EPA903-R-97-015
CBP/TRS 175/
1997
Chesapeake Bay
ry Manag
June 1
"H .EPA Report Collection
Information Resource Center
US EPA Region 3
Philadelphia, PA 19107
Chesapeake Bay Program
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FISHERY MANAGEMENT PLANS BACKGROUND
Chesapeake Bay fishery management plans (FMPs) are prepared under the direction of the
1987 Chesapeake Bay Agreement and serve as a framework for conserving and wisely using
fishery resources. Bay fisheries traditionally are managed separately by Pennsylvania, Maryland,
Virginia, and the District of Columbia. A Chesapeake Bay FMP provides a format for undertaking
compatible, coordinated management measures among the jurisdictions. In addition, it creates a
forum to specifically address problems that are unique to Chesapeake Bay. Habitat issues are
particularly important. The goal of Chesapeake Bay FMPs is to protect the reproductive capability
of a resource while allowing optimum harvest. The ecological, economic and sociological factors
affecting the resource must be considered in the process. Objectives include:
* determine biologically appropriate levels of harvest;
* identify habitat requirements and develop necessary protection and restoration measures;
* monitor and assess the status of the resource using fishery-dependent and independent
data;
* define management recommendations and identify effective enforcement procedures.
Development of a FMP is a dynamic, ongoing process. It begins with initial input by the
FMP Workgroup, which is under the Chesapeake Bay Program's (CBP) Living Resources
Subcommittee (LRSc). The FMP Workgroup consists of resource managers, scientists,
stakeholders, and conservationists. They evaluate the biological, economic and social aspects of a
particular resource; define problems and/or potential problems; and recommend strategies and
actions to address the problems. Throughout development, FMPs undergo scientific and public
review. The FMPs are adopted when signed by the Chesapeake Executive Council, the policy-
making body of the CBP. Upon adoption, the appropriate management agencies begin
implementing the recommended actions. In some cases, regulatory and legislative action must be
initiated to fully implement a management action. In other cases, additional funding and staffing
may be required. Progress of FMP implementation and status of the stock and fishery are updated
annually for each FMP species. As the status of a stock changes, management strategies are
changed accordingly. Amendments and revisions may be recommended by the FMP Workgroup
(see Appendix A for FMP revision and adoption schedule).
Internet Address (URL) • http://www.epa.gov
Recycled/Recyclable • Printed with Vegetable Oil Based Inks on Recycled Paper (20% Postconsumer)
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1997
Chesapeake Bay
Blue Crab
Fishery Management Plan
Prepared by
Blue Crab Fishery Management Plan Workgroup
Living Resources Subcommittee
Chesapeake Bay Program
June 1997
Printed on recycled paper by the U.S. Environmental Protection Agency
for the Chesapeake Bay Program
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Chesapeake Bay Program
CHESAPEAKE EXECUTIVE COUNCIL
ADOPTION STATEMENT
BLUE CRAB FISHERY MANAGEMENT PLAN
e, the undersigned, adopt the 1997 Chesapeake Bay Blue Crab Fishery Management
Plan. We agree to accept the 1997 Chesapeake Bay Blue Crab Fishery Management Plan as a guide to
conserving and protecting the blue crab resource for long-term ecological, economic and social benefits.
We further agree to work together to implement, by the dates set forth in the Plan, the management
actions recommended to address increased fishing effort, wasteful harvesting practices, stock assessment
deficiencies, regulatory issues, and habitat degradation.
We recognize the need to commit long-term, stable, financial support and human resources to the task
of managing the blue crab stock and addressing important research needs. In addition, we direct the
Living Resources Subcommittee to periodically review and update the plan and report on progress made
in achieving the plan's management recommendations.
Date June 4, 1997
CHESAPEAKE EXECUTIVE COUNCIL
FOR THE UNITED STATES OF AMERICA
FOR THE STATE OF MARYLAND
FOR THE COMMONWEALTH OF PENNSYLVANIA
FOR THE COMMONWEALTH OF VIRGINIA
FOR THE DISTRICT OF COLUMBIA
FOR THE CHESAPEAKE BAY COMMISSION
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Acknowledgments
The 7997 Chesapeake Bay Blue Crab Fishery Management Plan was developed under
the direction of the Blue Crab Fishery Management Plan (FMP) Workgroup, which is under the
Chesapeake Bay Program's Living Resources Subcommittee. The Blue Crab FMP Workgroup
and Living Resources Subcommittee would like to acknowledge the following groups who
significantly contributed to the development of this FMP:
• Chesapeake Bay Commission Bi-State Blue Crab Advisory Committee
and its Technical Workgroup
• Chesapeake Bay Stock Assessment Committee and its Subcommittee
• Submerged Aquatic Vegetation (SAV) Workgroup of the Living Resources
Subcommittee
• Habitat Objectives and Restoration Workgroup of the Living Resources Subcommittee
iv Acknowledgments
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TABLE OF CONTENTS
FORWARD viii
EXECUTIVE SUMMARY ix
GOAL STATEMENT AND OBJECTIVES xi
SECTION 1. BACKGROUND 1
Life History 1
Larval and Post larval Phases 1
Early Juvenile Stages 2
Adults arid Reproduction 2
Predator-prey Relationships 3
Biological Profile 4
Habitat Requirements 5
Vegetated and Unvegetated Shallow Water Habitats 5
Dissolved Oxygen Content 7
Fisheries 7
Commercial Fisheries 7
Commercial Fishing Effort 10
Recreational Fisheries 13
Stock Status 14
Abundance 14
Mortality and Exploitation 16
Chesapeake Bay Stock Assessment 16
Problems and Concerns 19
Fishing Pressure 19
Female Harvest 21
Male Harvest 21
Wasteful Harvesting Practices 22
International Trade and Implications for the Chesapeake Bay 23
Parasites and Disease 24
Water Quality 24
Submerged Aquatic Vegetation 25
Chesapeake Bay Program Efforts 27
Nutrient Reduction 27
Minimum Dissolved Oxygen Requirements 27
SAVand Wetland Protection and Restoration 28
Toxics Reduction Strategy 29
Research Needs 29
Table of Contents v
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SECTION 2. BLUE CRAB MANAGEMENT IN CHESAPEAKE BAY 52
Coordinated Baywide Management Efforts 52
Management Measures Since 1989 52
Virginia 52
Maryland 55
Potomac River Fisheries Commission 56
Improvements in Catch Statistics 56
Evaluation of Blue Crab Management 57
Conclusion 57
Blue Crab Management Strategies 59
1. Stock Status 59
2. Fishing Effort 60
3. Stock Assessment Needs 62
4. Wasteful Harvesting Practices 64
5. Regulatory Issues 68
6. Habitat Issues 69
REFERENCES 75
APPENDIX A. CHESAPEAKE BAY FMP ADOPTION SCHEDULE 87
APPENDIX B. DECISION MATRIX USED TO MAKE RECOMMENDATIONS
IN ACTION 6.2.2 88
APPENDIX C. LAWS AND REGULATIONS 90
APPENDIX D. GLOSSARY OF TERMS 97
APPENDIX E. PLAN DEVELOPERS AND CONTRIBUTORS 100
Blue Crab Fishery Management Plan Workgroup 100
Chesapeake Bay Stock Assessment Committee, Technical Subcommittee ... 101
Bi-State Blue Crab Advisory Committee, Technical Workgroup 102
vi Table of Contents
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TABLES AND FIGURES
Table 1. Participation and average harvest by license category for commercial crabbers in
Maryland for 1995 11
Table 2. Results of recreational surveys in Maryland 13
Table 3. Recreational crab licenses issued in Virginia, 1993 to 1996 14
Table 4. Strategies for SAV restoration and protection for postlarval blue crab settlement .... 73
Figure 1. Life history of the blue crab in Chesapeake Bay 32
Figure 2. Estimates of the total number of blue crabs in middle/lower Chesapeake Bay
vegetated habitats versus unvegetated habitats 33
Figure 3. Dissolved oxygen limitations for blue crab (Map) 34
Figure 4. Maryland commercial hard crab landings and dockside values 36
Figure 5. Virginia commercial hard crab landings and dockside values 37
Figure 6. Chesapeake Bay commercial soft and peeler crab landings 38
Figure 7. Effort and CPUE in Chesapeake Bay's blue crab fishery, 1945 to 1994 39
Figure 8. Distribution of commercial harvesters by crab pot use category in Maryland,
1991 and 1994 40
Figure 9. Maryland commercial license structure 41
Figure 10. Virginia commercial crab pot licenses 42
Figure 11. Virginia commercial dredge licenses 43
Figure 12. Virginia commercial trotline, scrape, and trap licenses 44
Figure 13. a. Landings from Virginia commercial dredge fishery 45
b. Adult female crab abundance from VIMS/W&M trawl survey 45
c. Commercial dredge harvest and adult female index regression 46
Figure 14. SAV recommendations to benefit blue crab postlarval settlement (Map) 48
Figure 15. Potential SAV habitat for blue crab (Map) 50
Table of Contents vii
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FORWARD
This 7997 Chesapeake Bay Blue Crab Fishery Management Plan serves four major
purposes, and depending on interests, the reader may want to focus on the relevant sections.
First, the Plan describes the nature and extent of the blue crab fishery on Chesapeake Bay. This is
covered in the Background section, pages 7-14, and includes hard crab, as well as soft and peeler
crab fisheries. Both commercial and recreational fisheries in the Maryland and Virginia portions of
the Bay are described.
Second, the Plan provides a framework for state actions to manage the blue crab as a
fishery. Stock status and analytical assessment, and concerns of the crab fishery are discussed on
pages 14-23. The elements of management are spelled out in the provisions of the Plan on pages
52-74. Although the framework identifies a number of areas where changes in the fishery should
result in management responses, no such actions would be triggered at this time from adoption of
the Plan.
Third, the Plan incorporates an innovative effort to identify specific geographic areas that
provide key habitat for the blue crab. Habitat requirements are identified on pages 5-7 in the
Background section. Pages 27-29 describe Chesapeake Bay Program habitat protection and
restoration goals and programs. Pages 69-74 of the management provisions of the Plan address
habitat issues; and Appendix B details the decision matrix used to guide habitat recommendations.
These habitat provisions are particularly important because, unlike other state and Federal fishery
management plans, Chesapeake Bay plans are signed by the Chesapeake Executive Council on
behalf of all applicable state and Federal authorities. This means that it is the responsibility of all
executive agencies, not simply the fishery management agencies, to carry out and abide by the
habitat protection and restoration provisions in the Plan.
Finally, the Plan outlines for the public the on-going scientific debate regarding the status
of the blue crab stock, the life cycle, and the effects of management actions on both. Much of the
discussion is related to studies still underway that are likely to be published in mid-1997. Once
available, these reports will help expand the discussion on blue crab biology and management. The
nature of the issues is outlined on pages 1-4 and 14-18 of the Background section; pages 29-31
regarding research needs; and pages 59-61 of the management section of the Plan, regarding
stock status and fishery effort. As the policy implications of these scientific findings are analyzed,
it may be appropriate to amend this fishery management plan to reflect any emerging consensus
on currently unresolved issues.
viii Forward
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EXECUTIVE SUMMARY
The blue crab stock behaves as one unit throughout Chesapeake Bay. A unified
management approach among Bay jurisdictions was initiated with the development of the 7959
Chesapeake Bay Blue Crab Fishery Management Plan (FMP). This FMP recognized the
importance of the resource, identified areas of concern, and recommended strategies to stabilize
fishing effort. Since 1989, new regulations have been implemented, commercial reporting has
improved, and additional data have been collected. In 1996, a Baywide stock assessment was
conducted and a targeting effort was initiated to define appropriate stock levels.
The 7997 Chesapeake Bay Blue Crab FMP incorporates new information and
management strategies. The overall goal has not changed substantially from the 1989 plan. The
goal is: to manage blue crabs in the Chesapeake Bay to conserve the baywide stock, protect its
ecological value, and optimize the long-term utilization of the resource. To achieve this goal, a
sustainable and prudent level of spawning stock must be maintained; regulations must adequately
protect the resource and optimize harvest; there must be fair allocation of the resource and
minimal conflict among user groups; data must be collected to monitor and manage the fishery;
research priorities need to be identified; submerged aquatic vegetation (SAV) should be protected
and restored in lower Bay nursery areas; and water quality should be improved.
This Plan is flexible and responsive to new knowledge, changes in fishing mortality rates,
and revised estimates of stock status. Major recommendations include: 1) restore and protect
habitat and water quality; 2) maintain regulations designed to stabilize the fishery and modify them
as necessary to achieve objectives of this Plan; 3) limit access to the fishery and lower the cost of
harvesting crabs; 4) prevent an increased rate of exploitation; 5) design and implement a survey to
estimate recreational catch and effort; 6) monitor the commercial fishery; 7) improve enforcement
of regulations; and 8) develop socioeconomic data collection to assess the social and economic
utilization of the blue crab resource.
A stock assessment conducted by the Chesapeake Bay Stock Assessment Committee
(CBSAC), not yet published, indicates that stock abundance during the 1980s was high and has
returned to average levels since 1991. Juvenile abundance has increased since the early 1970's,
and additional studies in Virginia indicate this may be correlated with the recovery of submerged
aquatic vegetation (SAV) in the lower Bay since the early 1980's. The blue crab fishery was
characterized as fully exploited, based on an estimated rate at which crabs are removed by the
fishery (fishing mortality rate) which allows for approximately 10% of the spawning stock (mature
females) to escape harvest (measured as 10% of the spawning stock in the absence of a fishery).
At present, there is no evidence of harvest exceeding sustainable limits (no recruitment
overfishing). This finding supports the need for caution. A fully exploited fishery should be
managed to prevent any further increase in the rate of fishing mortality. Since 1945, estimates of
fishing mortality varied without significant trend; however, fishing mortality did increase from
1990 to 1994, then declined in 1995. The Baywide stock assessment supports the need for
caution. In order to monitor trends and maintain the best possible understanding of the resource
and the fisheries, the Baywide stock assessment will be updated in two years, and every five years
thereafter. Additional studies will continue to be reviewed.
The CBSAC also evaluated effort in the Baywide commercial fishery. There has been a
major increase in commercial fishing effort since 1945, coinciding with a decrease in catch-per-
unit-effort (CPUE; example: crabs harvested per pot or yard of trotline). Most of this decrease
Executive Summary ix
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occurred between 1945 and 1970. A decline in CPUE can indicate a declining stock. However,
modeling efforts indicate that fishing mortality rates were stable over time and the decline in
CPUE was not indicative of decreased crab abundance, but rather, catch was distributed among
more pots as effort in the fishery continued to grow. Based on cumulative review of all the
current information, this FMP strongly recommends caution, noting that gear and participation are
currently at very high levels and any increase in fishing mortality could endanger the fishery and
the resource.
Our understanding of the blue crab is far from complete. The massive transport of crab
larvae out of the Bay and the subsequent return of variable numbers into the estuary may have
uncontrollable effects on the availability of crabs from year to year. Crab abundance may also be
affected by other environmental factors including the abundance of submerged aquatic vegetation
(SAV) habitat. In addition, there is investigation underway exploring whether the level of harvest
may be affecting the size distribution of crabs, resulting in a reduced total yield from the fishery
(growth overfishing). This issue will continue to be revisited in the next update of the Chesapeake
Bay Blue Crab Fishery Management Plan, the Baywide stock assessment and other investigations.
This plan sets forth general guiding principals based on the science as we know it today.
The partners of the Chesapeake Bay Program, which include Maryland, Pennsylvania, and
Virginia; the District of Columbia; the Chesapeake Bay Commission, a tri-state legislative body;
the U.S. Environmental Protection Agency (EPA), representing the federal government; and
participating citizen advisory groups, will continue to work towards meeting the goals of this plan
and furthering understanding of this complex animal. The plan is flexible and will be amended
periodically as we learn more about the blue crab population dynamics and the fishery in
Chesapeake Bay. The Chesapeake Bay Commission's Bi-State Blue Crab Advisory Committee
(BBCAC), with diverse membership from Maryland and Virginia, will continue to be a valuable
forum to assure complementary approaches to blue crab management among the jurisdictions and
insure that research needs are identified and pursued so that actions are timely and based on sound
science.
Executive Summary
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GOAL STATEMENT AND OBJECTIVES
The goal of the 7997 Chesapeake Bay Blue Crab Fishery Management Plan is to manage
blue crabs in Chesapeake Bay in a manner which conserves the Baywide stock, protects its
ecological value, and optimizes the long-term use of the resource.
To achieve the 7997 Chesapeake Bay Blue Crab Fishery Management Plan goal, the following
objectives must be met:
1. Maintain the stock of mature adult males and females at a size that minimizes low
reproductive potential (from harvest) as a cause of poor spawning success.
2. Maintain a clear distinction between conservation goals and allocation issues.
3. Minimize conflicts among user groups and between jurisdictions by coordinating
management efforts throughout Chesapeake Bay.
4. Promote a program of education and public information to help the public understand the
causes and nature of problems in the blue crab stock, its habitats and fisheries, and the
rationale for management efforts to solve these problems.
5. Develop a Baywide regulatory process that provides adequate resource protection,
optimizes the harvest, provides sufficient opportunity for recreational crabbers, and
considers the needs of other user groups.
6. Promote harvesting practices that minimize waste of the resource.
7. Restore and improve habitat and environmental quality to increase growth, survival and
reproduction of blue crab.
8. Identify and promote research to improve the understanding of blue crab biology, ecology
and population dynamics.
9. Initiate and/or continue studies to collect necessary economic, social, and fisheries data to
effectively monitor and manage the blue crab fishery.
Goal Statement and Objectives xi
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SECTION 1
BACKGROUND
The blue crab, Callinectes sapidus, is a dominant bottom-dwelling predator in estuaries,
lagoons and coastal habitats of the Western Atlantic, Caribbean and Gulf of Mexico (Williams,
1984). It is economically important throughout its range and has supported the largest single-
species crab fishery worldwide over the past decade (FAO, 1990). The blue crab harvest from
Chesapeake Bay accounted for over 50% of the national total during the late 1970s through the
early 1990s (Orth and van Montfrans, 1990). It consistently outranks harvests from other shellfish
species in Chesapeake Bay by weight and total dollar value. The recreational fishery also
contributes to the economy of the region and is believed to be significant, though the value is
currently unknown. Thus, the blue crab is an important natural resource requiring sound
management to protect its long-term health and ecological, social and economic benefits.
Life History
Larval and Postlarval Phases
In Chesapeake Bay, larvae (zoeae) are released by mature females in high-salinity water
near the mouth of the Bay (Van Engel, 1958; refer to life cycle in Figure 1). Larvae are
transported to the continental shelf, where development proceeds for about 30-45 days, through
seven or eight developmental stages (reviewed in Millikin and Williams, 1984; McConaugha et
a/., 1983; McConaugha, 1988). Larvae feed on zooplankton and plant material (Truitt, 1939).
High salinities in excess of 30 parts-per-thousand (ppt) are required for optimal development
(Costlow, 1967). Physiologically, larvae are poorly adapted to undergo proper development at
salinities much below 26 ppt, emphasizing the need for larval development in an oceanic
environment.
Change to the postlarval (megalopae) stage occurs on the near-shore Atlantic shelf
(Epifanio et al., 1984). A retention mechanism has been postulated for blue crabs inhabiting
western Atlantic estuaries such as Chesapeake Bay (McConaugha et al., 1983). This process
involves a southerly flow of water that traps and carries larvae south. At the same time, a
counter-current and wind-generated surface flow move larvae in a northerly direction. The
interaction between the southerly and northerly currents creates a circular pattern that prevent
larvae from being swept too far from the entrance of Chesapeake Bay.
In many marine species, larval or postlarval abundance and settlement into nursery areas
determines population size. Blue crab postlarval abundance, though highly variable in the Bay,
generally follows a neap-spring tidal cycle, with brief periods of high abundance following spring
tides by several days. Superimposed on this fortnightly pattern are peaks of abundance related to
wind events that transport megalopae towards the coast and into Chesapeake Bay (Goodrich et
a/., 1989). It is unknown if larvae hatched from adult females in adjacent coastal waters and
nearby estuaries are swept into the Chesapeake Bay in significant numbers or how they may
influence stock abundance. It is possible that weather events, such as hurricanes, may effect
offshore currents and consequently impact the number and origin of crab larvae entering the Bay
mouth during particular years.
Background 1
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Once within Chesapeake Bay, megalopae migrate vertically in response to light and tide.
They utilize nocturnal flood tides to assist transport up the estuary to shallow estuarine nursery
habitats (Olmi, 1993). During transport into the Bay, megalopae undergo physiological changes
which prepare them for the metamorphic molt into the first juvenile instar (Lipcius etal., 1990;
Metcalf and Lipcius, 1992).
Settlement of blue crab postlarvae was assessed in the lower portion of Chesapeake Bay
using artificial surfaces. Settlement occurs primarily between July and mid-November each year. It
is characterized by episodic pulses during periods surrounding full and new moons (Orth and van
Montfrans, 1987; van Montfrans el al., 1990). The potential exists that these episodic settlement
peaks, which account for more than half the annual total of blue crab postlarvae that enter into the
Bay, may be the major determinants of adult population size. Low, but continuous, settlement
over the summer and early fall and may also influence population size. Collection of postlarvae
from surface water and near the bottom may provide a measure of planktonic abundance and
postlarval settlement (van Montfrans et al., 1990; van Montfrans et al., 1995).
Early Juvenile Stages
Late premolt postlarvae settle in the lower Bay and utilize beds of submerged aquatic
vegetation (SAV, also called Bay grasses) as nursery areas until approximately the fifth juvenile
instar (Orth and van Montfrans, 1987; Pile et al., 1996). Large juveniles migrate out of grass beds
and are found in greatest abundance upriver, in lower bay tributaries. Eventually, they begin
appearing in upper-Bay Maryland waters. This evidence suggests lower salinity areas are
important for larger juvenile crabs, which ultimately grow and segregate by habitat. Large males
generally occupy the upper reaches of tributaries and the Bay; whereas, females remain in higher
salinity regions of the lower Bay and lower reaches of the tributaries (Hines et al., 1987).
Adults and Reproduction
Blue crabs mature at approximately 12 to 18 months of age (Van Engel, 1958). Under
current levels of fishing pressure, most crabs live from one to two years beyond maturity and the
typical lifespan of a crab is up to 3 years. However, the maximum age may be as long as 5-8 years
based on a few tag returns (Fischler and Walburg, 1962; Fischler, 1965; McConaugha, 1991;
McConaugha, 1993; McConaugha, unpublished). Most mating occurs from May through October
in lower- and mid-Bay habitats, where salinity preferences for males and females overlap. Female
crabs molt preceding maturity at approximately 4.5 inches in carapace length (115 mm; measured
from spine to spine; Knotts, 1989). The average size of an adult female is 6.1 inches (155 mm;
Knotts, 1989; Hines et al., 1987) and one hundred percent maturity is observed in female crabs
5.2 inches (130mm) and greater (Rothschild et al., 1992). Growth of female crabs is believed to
cease after the last molt preceding maturity (the terminal molt; Van Engel, 1958); however, there
is evidence that some females may attempt to molt again (Havens and McConaugha, 1990;
Rugolo et al., unpublished). Adult female crabs found molting in the wild are rare. Documented
specimen of mature female peeler crabs were preserved before molting was complete and is is not
known whether those crabs would have survived to become hard crabs (Abbe, 1974; Casey,
unpublished).
Male crabs "cradle" the females during the molt preceding maturity and guard them until
the new shell hardens. Mating takes place while the female is in her soft-shell phase. After the
2 Background
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pairs separate, males remain in lower salinities of the Bay and tributaries. Females migrate to
higher salinities of the lower Bay, where they develop an orange, external egg mass beneath their
aprons which may contain 750,000 - 8,000,000 eggs, depending on crab size (Prager et al.,
1990). The egg mass darkens over a two-week period as the orange yolk is consumed by the
developing larvae. Larvae develop large, black eye spots as hatching approaches. Spawning is
protracted and occurs over a period of one or two weeks. Spawning occurs from May to
September, with a minor peak in June and a major peak in July and August (McConaugha et al.,
1983; Jones et al., 1990). Individual females may spawn more than one time, depending on the
amount of sperm transferred during mating (Jivoff, 1995; Prager et a/., 1990). Successive spawns
may occur during the same year or females may overwinter before spawning again the following
spring. Early reproductive females generally spawn prior to the coming winter; whereas, those
maturing later spawn the following spring. Most males and many juveniles remain in lower
salinities of the mid- to upper-Bay and tributaries and overwinter in the sediment. Females
overwinter in the mid- and lower-Bay mainstem and at entrances of lower Bay tributaries.
Predator-prey Relationships
Blue crabs serve as both predator and prey in the benthic and planktonic food webs of
Chesapeake Bay. Postlarvae in the water column (Olmi, 1993) are a food source for plankton
feeders. Settled postlarvae and juveniles are eaten by eel, drum, spot, croaker, striped bass, sea
trout and catfish. Some sharks and cownose rays feed on juveniles and larger crabs. The federally
endangered species, Atlantic Ridley sea turtle (Lepidochelys kempi), migrates to the Bay every
summer for its preferred food, blue crab. Cannibalism of young blue crabs by larger crabs is
common (Mansour, 1992) and may regulate population abundance. Recent concern has been
raised over the recovery of striped bass, which prey on blue crabs. Goshorn and Casey (1993) and
Mosca et al. (1995) examined the relationship between striped bass abundance and blue crab
landings in Chesapeake Bay and found no significant relationship. Instances where blue crabs are
plentiful in the stomachs of striped bass are probably the result of opportunistic feeding (Booth
and Gary, 1993), though the impact remains to be quantified.
Adult blue crabs feed on bivalves, crustaceans, fish, annelids, plants and detritus (Darnell,
1958; Tagatz, 1968; Alexander, 1986). Although the blue crab is an opportunistic predator that
feeds on commonly occurring bottom dwellers (Laughlin, 1982; Mansour, 1992), recent research
indicates that thin-shelled bivalves (e.g., Macoma spp. and Mya arenarid) are preferred food.
Evidence suggests that blue crabs may control some bivalve populations (Lipcius and Hines,
1986; Eggleston, 1990; Eggleston et al., 1992; Mansour and Lipcius, 1993). When bivalves
become depleted, cannibalism on juvenile crabs increases (Mansour, 1992). Cannibalism may
serve as a self-regulating control on crab populations, particularly during periods of high crab
abundance or low alternative prey abundance (Mansour and Lipcius, 1993).
Background 3
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Biological Profile
Natural Mortality Rate 0.375 (Rugolo et al, unpublished)
Fecundity 750,000 to 8,000,000 eggs per spawn, may spawn 2 to 3 times.
Longevity Typical life span: about 3 years
Possible maximum life span: 5 to 8 years
Egg and Embryonic Development
Egg Bearing Season Females bearing external eggs ("sponges") occur May through
September
Area Egg bearing females are present infrequently in Maryland waters.
Presence is limited at salinities of 15-20 ppt (e.g. between the
mouth of the Potomac River and Wolf Trap Light), and most
abundant in the lower Bay and the mouths of the Bay's southern
rivers where characteristically higher percentages of females occur..
Embryonic Dev. Hatching is limited between the mouth of the Potomac River and
Wolf Trap Light, and increases substantially southward to the Bay
mouth and slightly beyond. It may take up to 45 days at 16°C and
10-12 days at 26°C (60-79°F). The incidence of dark sponges,
indicating late embryological stages, increases toward the Bay
mouth.
Larval Development
Transport Larvae are transported out of the lower Bay to the continental shelf
where most larval development occurs.
Zoeal Development Development of zoeae generally occurs from the southern end of
the Bay out to 40 miles in the coastal ocean. The highest rate of
growth and survival occur at salinities of 26 to 33 ppt and
temperatures of 66-84°F (19 to 29°F). Survival is limited below
26°C and 20 ppt. Once transformed, the megalopa stage reinvades
the Bay through wind generated transport, tides and changes in
behavior.
Postlarvae and Early Juveniles
Recruitment Generally occurs in the post-larval phase which invades estuaries
from the coastal ocean thereby establishing the new year class.
Location Lower and central Chesapeake Bay, primarily shallow water in beds
of submerged aquatic vegetation. Migration to the upper Bay and
tributaries may begin as early as September through November; late
migration begins the following spring.
Background
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Biological Profile (continued)
Subadults and Adults
Location Chesapeake Bay from Virginia Capes to tidal freshwater.
Salinity 0 to 33 ppt. Males most abundant in 3 to 15 ppt salinity;
females most frequently found in > 10 ppt. Most mating
occurs where salinity preferences overlap.
Temperature Upper limit approximately 90° F (32° C)
Dissolved Oxygen Recommended goal for selected Bay species, including blue
crabs, is 5.0 mg/L monthly average; however, juvenile blue
crabs are less tolerant than adult crabs and may need as much
as 6.0 mg/L monthly average or more.
Habitat Requirements
Vegetated and Unvegetated Shallow Water Habitats
Submerged aquatic vegetation (SAV) and other shallow water habitats are utilized by blue
crabs during postlarval settlement (Orth et al., 1996), juvenile development (Orth and van
Montfrans, 1987) and overwintering (Orth and van Montfrans, 1987; Montane et al., 1994), as
well as for protection during molting and soft shell phases of all size classes (Ryer et al., 1990).
Lower Chesapeake Bay SAV beds are most important for postlarvae and juvenile crabs (Heck and
Thoman, 1981; Penry, 1982; Heck and Wilson, 1987; Orth and van Montfrans, 1987; Orth et al.,
1996; Wilson et al., 1987; Montane et al., 1994). SAV beds comprised ofZostera marina
(eelgrass) and Ruppia maritima (widgeon grass) fall within the salinity range of invading
postlarvae. Orth et al. (1996) identified SAV beds within the range of postlarval blue crab
settlement.
Several studies documented that postlarval and juvenile blue crabs prefer SAV and similar
structural habitat over unvegetated shallow-water habitats (see Figure 15 for SAV bed locations).
Field tests of postlarval response to mud, live oysters, and live eelgrass found a significant
preference for eelgrass (Orth et al., 1996). Samples taken over ten years from mud, sand, marsh
creek, and SAV habitats found higher densities of blue crabs in SAV (Penry, 1982; Orth and van
Montfrans, 1987; Montane et al., 1994). Similarly, a study in Virginia's coastal lagoons found
that densities of newly settled larvae in sunken mats of macroalgae (commonly called seaweed)
are comparable to larval densities in lower Chesapeake Bay SAV beds (Brumbaugh, 1996). Small
juvenile crabs are five times more abundant in SAV than in adjacent unvegetated habitats (Orth et
al., 1996). Calculations of the total areal coverage of SAV and unvegetated habitats in waters less
than six feet (2 m) in depth were used to estimate juvenile abundance in each habitat. Total area
covered by unvegetated bottom is approximately five times greater than that of SAV (Figure 2a).
Juvenile crab density is approximately 30 crabs per square meter in SAV and only one crab per
square meter in unvegetated habitat (Figure 2b). Despite significantly higher coverage of
Background
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unvegetated bottom in Chesapeake By, more juvenile blue crabs were found in SAV (an estimated
2.7 billion crabs) than in unvegetated habitats (approximately 0.6 billion crabs; Figure 2c).
Postlarval and juvenile blue crabs prefer SAV and macroalgae over other available habitats
because they provide structure where postlarvae and juvenile crabs can hide from predators.
Studies in the lab and in the field show shallow water with no structural cover offers only partial
refuge for small crabs (Dittel et al., 1995). Predation rates of larvae in macroalgae mats are lower
than in "unvegetated" or open habitat with no refuge and macroalgae may be an important
settlement and refuge habitat in coastal areas (Brumbaugh, 1996). Predation of postlarvae and
juvenile crabs in SAV habitat was documented (Orth et al., 1996) and survival of young crabs
was higher in SAV than in unvegetated habitats (Pile, 1993). Metcalf et al. (unpublished data;
reviewed in Orth et al., 1996) suggest that the high density of postlarvae and juvenile crabs in
SAV habitat may insure that a greater proportion survive predation.
The geographic location of lower Bay SAV habitats offers another advantage to
postlarvae as they enter the Bay estuary. SAV beds are situated in shallow water between marshy
shores or creeks and deep open water. Grass beds are the first shallow-water refuges postlarvae
encounter. The faster postlarvae can take refuge, particularly in areas where postlarval density is
already high, the less likely they are to be preyed on.
Predation of juvenile crabs decreases with increasing crab size. Therefore, the faster crabs
molt to larger size classes, the less likely they are to be preyed on. Research indicates that
chemical cues from eelgrass are detected by postlarvae and induce molting to the first juvenile
crab stage (reviewed in Orth et al., 1996). In addition, molting frequency of juvenile crabs is
higher in SAV than in adjacent marsh creek habitat (Ryer et al., 1990). SAV probably provides
the greater food availability needed by young, growing crabs (Orth et al., 1984; Orth et al.,
1996).
Vegetative cover in much of the upper Bay is relatively sparse, when compared with the
lower Bay. The Rhode River is a small tidal tributary on Maryland's lower western shore. Ruiz et
al. (1993) found that adult blue crabs had significantly higher density in SAV beds in the Rhode
River than in nearby unvegetated areas; however, there has been little SAV in the Rhode River in
recent years. As juvenile crabs grow and disperse, they utilize other shallow-water habitats, as
well as SAV. Tidal guts of small creeks and rivers in and around salt marshes provide shallow-
water habitats for larger juveniles and mature crabs to feed and take refuge during molting (Orth
and van Montfrans, 1987; Hines et al., 1987; Thomas et al., 1990). Coarse woody debris (pieces
of wood over 2 centimeters or 0.8 inches in diameter) in shallow waters adjacent to forested
riparian zones provide valuable shelter for large crabs, particularly during molting phases, when
SAV is not present (Everett and Ruiz, 1993; Wolcott and Hines, 1989).
Habitat studies of American lobster, Homarus americanus, in Maine indicate that
availability of larval settlement habitat is the factor that determines the population size. Habitat
availability is even more important than larval entry into inshore waters, because larval entry is
influenced by annual weather patterns (Wahle and Steneck, 1991; 1992). Young lobster prefer
cobble bottoms, where they can hide from predators. They suffer high mortality in open habitats
of sand and mud (Wahle and Steneck, 1991). Juvenile blue crabs may also require shelter to
escape predation. Mortality of juvenile crabs is much higher in deep water and shallow water
habitats devoid of vegetative cover offer only partial refuge. Based on current research, SAV is
believed to be the primary structural habitat utilized by postlarvae and juvenile blue crabs in the
6 Background
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lower Bay. Some investigation of the importance of oyster reef habitat for blue crab has been
conducted; however, this habitat has been severely reduced in Chesapeake Bay due to
overharvesting, poor water quality and disease (CBP, 1994a).
Dissolved Oxygen Content
Jordan et al. (1992; based on Funderburk et al., 1991) recommended a monthly average
dissolved oxygen content of 5 mg/L for target species in Chesapeake Bay, which included blue
crabs. Blue crabs are tolerant of hypoxic (low oxygen) conditions; however, oxygen content less
than 0.5 mg/L at 77° F (25° C) is lethal within 4.3 hours (Lowery and Tate, 1986). Crabs exposed
to dissolved oxygen levels of 3.0 mg/L showed no mortality after seven days and less than 20%
mortality after 25 days, at approximately 70° F (20° to 21° C); however, tolerance decreased with
increasing temperature (dejFur et a/., 1990). Figure 3 depicts Baywide distribution of areas where
hypoxic and anoxic waters with a dissolved oxygen content of 3 mg/L or less frequently occurs
(Chesapeake Bay Program monitoring data, 1985 to 1994).
Juvenile crabs may be less tolerant of hypoxia than adults (Stickle eta]., 1989). Juvenile
mortality was 50% during 28 days of exposure to dissolved oxygen levels of 5.65 mg/L at 86° F
(30° C) and juvenile crabs may require more oxygen than was recommended by Jordan et al.
(1992) for other target species in Chesapeake Bay. Although dissolved oxygen tolerance limits for
larvae and postlarvae are unknown, they are not as likely to experience episodes of low dissolved
oxygen in the Atlantic Ocean or lower Chesapeake Bay.
Fisheries
Commercial Fisheries
The blue crab supports the largest single-species crab fishery worldwide in terms of
landings (FAO, 1990). The crab catch has the highest value of any Bay commercial fishery and
supports a recreational fishery of significant but undetermined value. Blue crabs are harvested as
hard shell crabs, peeler crabs just prior to molting, and soft shell crabs immediately after the molt.
Male crabs and immature female crabs are legal to harvest at 5 inches (127mm) in carapace width
as hard crabs. No size limits exist for mature female crabs. The minimum size for peeler crabs in
Maryland and the Potomac River is 3 inches; Virginia has no size limit on peeler crabs. Soft crabs
must be a minimum size of 3 l/2 inches (88mm) in Virginia, Maryland, and the Potomac River.
Hard Crab Fisheries
The hard crab fishery represents the largest commercial component of the crab fishery in
Chesapeake Bay, both in terms of total dollar value and quantity landed. Annual commercial hard
crab landings average 46 million pounds in Maryland (MDNR unpublished data, 1981 to 1995;
Figure 4; preliminary landings for 1996, 36.1 million Ibs.) and 40 million pounds in Virginia
(VMRC unpublished data, 1981 to 1995; Figure 5; preliminary landings for 1996, 32.5 million
Ibs.), for a baywide total of 86 million pounds. Recently, Chesapeake Bay landings have fluctuated
from a low of 53 million pounds in 1992 to a high of 107 million pounds in 1993. Baywide
landings in 1995 were below average (68 million pounds), and landings in 1994 were only slightly
below average (75 million pounds). Commercial reporting in Virginia and Maryland became
mandatory for all commercial harvesters in 1993 and 1994, respectively. Comparisons of the new
Background 1
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and old reporting system in Maryland give similar estimates of landings (MDNR unpublished data,
1994 to 1995). Virginia's voluntary reporting system provided landings estimated to be between
40 to 50% below actual landings (Vance, 1982; Rhodes and Shabman, 1994). Because Virginia's
new reporting system is mandatory and collects data from all harvesters, it is believed to be more
accurate (VMRC unpublished data, 1993 to 1995).
Principal techniques for commercially harvesting hard crabs include trotlines, crab pots
and dredges. The crab pot is the most widely used gear throughout Chesapeake Bay and harvests
approximately 60% of hard crabs landed in Maryland and over 80% of hard crabs landed in
Virginia. Crab pots catch both male and female crabs; male crabs represent a greater proportion of
the harvest in the upper portions of tributaries and upper Bay mainstem and female crabs
represent a greater proportion of the harvest in southern Maryland and Virginia. Female crabs
comprise approximately 40% of hard crab landings in Maryland (MDNR unpublished data, 1981
to 1995) and approximately 60% of hard crab landings from the crab pot fishery in Virginia
(VMRC unpublished data, 1993). Nearly all mature females are fertilized and carry eggs either
internally or during later stages as an external sponge. Sponge crabs represent a portion of the
crab pot harvest in the lower bay in Virginia during summer months and make up a very small
percentage of the population in Maryland, where they are illegal to harvest. In 1996, Virginia
placed restrictions on the harvest of late stage sponge crabs bearing brown and black eggs. Early
stage sponge crabs bear orange then yellow eggs.
Trotlines harvest approximately 40% of hard crab landings in Maryland (MDNR
unpublished data, 1981 to 1995), where commercial crab pots are prohibited in tributaries. The
Maryland trotline fishery primarily targets larger males in tributaries, though some females are
harvested in the lower reaches of tributaries. In Virginia, crab pots are permitted in tributaries and
trotlines are not commonly used.
The winter dredge fishery occurs exclusively in Virginia, in limited areas of the lower and
middle Bay mainstem. Dredges target hard crabs that overwinter in deeper water and the harvest
is estimated to consist of between 85% and 98% mature, inseminated female crabs (Van Engel,
1962; Schaffher and Diaz, 1988). The baywide winter dredge survey found 53.5% of adult female
crabs overwintered within commercial dredge boundaries in 1993 (see Volstad et al., 1994). Total
harvest by the winter dredge fishery is small compared with the hard crab pot fishery. Dredge
harvest averages approximately 7 million pounds and accounts for less than 20% of hard crabs
landed annually in Virginia (VMRC unpublished data, 1981 to 1995); whereas, crab pot landings
average approximately 32 million pounds (VMRC unpublished data, 1981 to 1995) and are
comprised of approximately 60% female hard crabs (VMRC unpublished data, 1993).
Dockside values for hard crabs have increased over recent years (Figures 4 and 5).
Dockside values in Maryland ranged from $18.0 million to $36.1 million during 1990 to 1995
(MDNR data; preliminary value for 1996, $25.2 million). In Virginia, the dockside value of hard
crabs doubled between 1993 and 1995. Dockside values in Virginia range from $9.1 million to
$30.6 million during the period 1990 to 1995 (VMRC unpublished data). Male crabs bring a
higher price per pound than female crabs. The average dockside value of large male hard crabs
(#1 males) in Maryland has increased from $0.73 per pound in 1990 to $1.29 per pound in 1995.
As a result of their greater value over female crabs, male crabs have experienced higher fishing
pressure, particularly in Maryland where they are most abundant (Casey et al., 1991). However,
the price of female crabs also has increased over recent years. In 1990, the average dockside value
8 Background
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for female hard crabs in Maryland was $0.23 per pound; prices steadily increased to $0.71 per
pound by 1995 (MDNR data). Price increases may be due to the discovery of Asian markets,
which prefer egg-laden crabs and the increasing demand for female crabs in live markets, where
male crabs have been priced out of many customers' range. Historically, the primary market for
female crabs has been picking houses where crabs are steamed and the meat is picked and
processed for container sale.
Soft and Peeler Fisheries
Annual landings of soft and peeler crabs average 2 million pounds in Maryland and 1
million pounds in Virginia (Figure 6; MDNR unpublished data, 1981 to 1995; preliminary 1996
landings in Maryland, 1.8 million Ibs.; VMRC unpublished data, 1981 to 1995; preliminary 1996
landings in Virginia, 1.7 million Ibs.). Available data suggest that landings of soft and peeler crabs
have increased since 1987. Virginia, however, relied on a voluntary data reporting system prior to
1993. Virginia's mandatory reporting system, in place since 1993, has produced a more complete
record of landings data and soft and peeler landings have averaged 1.6 million pounds through
1995 (VMRC unpublished data, 1993-1995).
Dockside values for soft and peeler crabs in Virginia also increased significantly in 1993
(Figure 6). Total dockside values from 1990 to 1992 averaged $1.7 million; from 1993 to 1995,
total dockside values averaged $3.6 million (VMRC unpublished data, 1990 to 1995). Dockside
values for soft and peeler crabs in Maryland have varied without trend and ranged from $1.6
million to $4.7 million during the period 1990 to 1995 (Figure 6; MDNR unpublished data, 1990
to 1995). However, the average price per pound for soft and peeler crabs steadily increased from
$2.34 per pound in 1990 to $2.81 in 1995 (MDNR unpublished data, 1990 to 1995). Although
soft and peeler crabs are a high value product, the process of holding crabs in shedding tanks is
labor intensive and overhead costs are greater than for the hard crab fishery.
Scrapes, peeler pots and peeler pounds/traps are used for the capture of soft crabs and
peeler crabs for the soft-shell and bait industries. Peeler crabs are also harvested as bycatch when
they enter hard crab pots. Peeler pots are the primary gear in Virginia, however, harvest by peeler
pots versus hard crab pots is unknown in Maryland. Virginia established a separate license for
peeler pots in 1994. Peeler crabs are harvested throughout spring and summer and peak harvest
occurs in the spring during "peeler runs" in both Maryland and Virginia. Crabs stop feeding when
they are close to molting; however, unbaited peeler pots are attractive refuge sites for molting
crabs. A common practice is to bait peeler pots with a live male "jimmy" crab to attract female
crabs just prior to their molt before maturity. Baited trotlines and hard crab pots also attract male
hard crabs cradling female peeler crabs. Soft and peeler crab harvest is not reported by sex,
however, harvest is believed to be largely immature female crabs. The impact of this fishery on the
blue crab population is difficult to assess due to inadequate reporting methods in the past. Peeler
crabs held in shedding tanks after their initial harvest may suffer high mortality, if not cared for
properly, and the extent of this mortality is currently unknown.
Background
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Commercial Fishing Effort
Baywide
Commercial fishing effort was estimated Baywide from 1945 to 1995 (Rugolo et al,
unpublished). Early data was obtained from Fisheries Statistics of the U.S. (Bureau of
Commercial Fisheries and NMFS, 1945 to 1989), and later estimates were derived from fisheries
statistics collected by the states (MDNR unpublished data, 1981-1995; VMRC unpublished data,
1973-1995). Effort was standardized to crab pots by dividing calculated values of catch per pot
into the total harvest by all gears to give estimates of nominal effort baywide. Baywide, nominal
effort increased five-fold from an estimated equivalent of 100,000 commercial crab pots at the
start of the time series, to a range of 500,000 to 600,000 commercial crab pots in the last decade
(Figure 7).
Maryland
Maryland has collected data on commercial fishing effort since 1981 and has seen
increases in commercial effort, particularly since 1992. The average number of pots during any
given month of the season in Maryland waters has grown from approximately 94,400 in 1991 and
1992, to approximately 130,000 in 1993 and 1994. The cause of this recent increase is seen in
Maryland's commercial reports, where harvesters record the number of pots in the water each
month. In 1991, most harvesters reported fishing 101 to 200 pots per person. In 1994 (the first
year pot limits were in place in Maryland), more people reported fishing 201-300 pots and greater
(Figure 8).
Increase in total gear fished and high effort extended over a greater portion of Maryland's
crabbing season may explain the exceptional harvest in 1993 and the average harvests in 1994 and
1995. These high harvests were in spite of reduced abundance since 1991, as indicated by fishery-
independent trawl and dredge surveys (Rugolo et al., unpublished). Another possible shift in
effort that has not been investigated is the movement from part-time and seasonal participants to
full-time harvesters dependent solely on blue crab harvest. As alternative fisheries closed or
became less profitable, license-holders may have shifted their efforts to harvesting blue crabs.
Three major license categories for commercial crabbing in Maryland currently exist. They
include the Limited Crab Catcher License (LCC), which permits the use of trotlines and up to 50
crab pots; the Crab Harvester License (CB3), which allows for the use of trotlines and up to 300
crab pots; and the Tidal Fish License (TFL), which is a consolidated license for the harvest of
fmfish and shellfish, including blue crabs with trotlines and up to 300 crab pots. Both CB3 and
TFL licensees may purchase additional allocations for the use of up to 600 pots (1 allocation) or
up to 900 pots (2 allocations), with the assistance of one or two unlicensed crew members,
respectively. Of the 6,646 commercial licenses issued in 1995 which permit crabbing, 73% (4,863)
were LCCs, 3% (205) were CB3s, and 24% (1,578) were TFLs. TFL license-holders landed the
largest portion of blue crab harvest in 1995. More specifically, TFL licensees permitted to fish up
to 900 pots landed 44% of the total blue crab harvest. The second largest portion of blue crab
harvest in 1995 was by LCC licensees (23%); CB3 licensees landed only 5.1% of the total blue
crab harvest (Figure 9).
LCC license-holders are largely part-time crabbers. Recreational crabbers are not allowed
to sell their catch or harvest more than one bushel per day for personal use. If a crabber wishes to
10 Background
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sell any portion of the catch, then that person must purchase an LCC or other commercial license.
Some recreational crabbers who wish to harvest more than one bushel per day for personal use
also hold LCC licenses. Harvest by CB3 license holders in Maryland with no allocations for
additional crab pots was less than 10,000 pounds per person (average). The low harvest is an
indication of part-time participation by a significant portion of license-holders (Table 1). When
averaged, harvesters with a TFL license with no allocations harvested more than 10,000 pounds
per person, indicating that a greater portion of these participants are full-time crabbers (Table 1).
Licensees with one and two allocations in both CB3 and TFL license categories harvested
significantly more per person and reflects greater full-time participation by licensees in these
categories (Table 1).
In 1994, Maryland law prohibited the sale of commercial licenses after April 1, 1996, after
which, a maximum allowable number of licenses must be determined. Depending on what level
commercial licenses are capped at, no new licenses will be issued unless the number of valid
licenses falls below the limit. Commercial licenses at the end of April, 1996, totaled 6,942 (4,872
LCC; 237 CB3; and 1,833 TFL). Despite the license moratorium, there is still potential for
growth in the commercial blue crab fisheries. Across all license categories, only 60% of
commercial license holders reported actually crabbing in 1995 (see Table 1 for participation by
license category). This indicates that 40% of licensed commercial crabbers did not participate in
the fishery. Non-participating license-holders represent a potential avenue for future growth. In
addition, many license-holders authorized to fish up to 600 and 900 pots are not taking full
advantage of their gear allocations. For example, during peak months of the crabbing season in
1995 (June through August), 420 TFL and CB3 licensees were authorized to use up to 900 crab
pots. However, only 96 licensees reported actually using more than 600 pots in June; 81 in July;
and 80 in August. Maryland's limited entry legislation expires in 1999 and if not renewed, the
fishery will return to open-access with a two-year delayed-entry program.
Table 1. Participation and average harvest by license category for
commercial crabbers in Maryland for 1995.
License Type
LCC
CB3
+1 allocation
+2 allocations
TFL
+1 allocation
+2 allocations
% of license holders who
reported harvest
61%
58%
72%
67%
57%
80%
83%
Average
Lb./person
2,659
8,627
13,364
33,156
10,917
24,087
52,053
Background 11
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Virginia
Virginia requires all commercial fishermen to purchase a Commercial Registration license
for $150, prior to obtaining a license for a specific gear. The Commercial Registration license
went into effect January 1, 1993, and a two-year delay process was also established for new
entrants to the commercial fisheries. The Commercial Registration license identifies the
commercial fishermen and facilitates the operation of the mandatory reporting system. In 1993,
3,837 commercial registration licenses were issued, 3,066 were issued in 1995, and 3,070 were
issued in 1996 (VMRC unpublished data, 1993 to 1996).
Crab pots are currently the principal commercial gear for catching crabs in Virginia tidal
waters and account for 80-90% of the hard crabs harvested (VMRC unpublished data). In 1996,
1,741 crab pot licenses were issued in Virginia, compared to 1,642 crab pot licenses in 1995 and
1,574 crab pot licenses in 1994 (Figure 10; VMRC unpublished data). Mandatory reporting data
from 1993 to 1995 reveal that 50% of licensed commercial crabbers in Virginia use 100 crab pots
or less per person (includes hard crab pots and peeler pots; VMRC unpublished data, 1993 to
1995). A 1992, socioeconomic study of Virginia's crab pot fishery estimated that 32.6% of
licensed crab potters derived no income from crabbing and utilized their license privileges for
personal use only (Rhodes and Shabman, 1994). Rhodes and Shabman characterized Virginia's
crab pot fishery as, "...an extremely diverse fishery, with vessel ages ranging from new to over 60-
years-old and with numbers of pots fished ranging from one to 600. The average boat length is 24
feet, demonstrating the small scale of most license holders. There is a relatively small group
(about 16% of license holders) who are large scale operators, but general indications are that this
is not a capital intensive fishery, with much high-tech equipment and many big operators." From
1993 to 1995, 20% of Virginia crab potters fished between 150 and 200 pots, 16% fished
between 250 and 350 pots, and only 5% of crab potters fished between 400 and 500 pots .(VMRC
unpublished data, 1993 to 1995).
In 1996, Virginia adopted restrictions on the sale of crab pot and peeler pot licenses,
thereby limiting effort in the crab pot fisheries. A commercial peeler pot license was established in
1994; 506 licenses were issued and sales increased to 585 in 1995 and 739 in 1996 (VMRC,
unpublished data). The Commercial Registration license fee discouraged some participants in
Virginia's crab pot fishery and many participants purchased a recreational license in place of the
commercial license. Figure 10 shows an apparent decline in the number of crab pot licenses in
Virginia; however, when the amount of peeler and recreational pot licenses are included, as they
were prior to 1994, the amount of pots used to harvest crabs is, in fact, still on the rise.
In 1993, a limited entry program was established for the Virginia crab dredge fishery. The
1993/94 dredge season was designated as a window of opportunity for anyone who wanted to
participate in the fishery. Consequently, the number of licenses sold during this dredge season
slightly increased. Beginning with the 1994/95 season, no crab dredge licenses will be issued to
any new applicant until the number of licenses drops below 225. Licensees must be actively
engaged in the fishery in order to retain their license. The number of crab dredge licenses sold in
1996 declined to 287, from a high of 375 in 1994 (Figure 11; VMRC, unpublished data, 1994-
1995).
Other types of gear used to commercially harvest crabs in Virginia include trotlines, crab
scrapes and crab traps (Figure 12). In 1996, only 20 commercial trotline licenses were sold,
indicating that trotlines are not an important commercial gear in Virginia. Crab scrape license
12 Background
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numbers have declined from a high of 447 in 1992, to 193 in 1995 and 205 in 1996 (VMRC,
unpublished data, 1992-1995). Likewise, crab trap numbers have steadily declined from 3,023 in
1980, to 1,787 in 1995 and 1,849 in 1996 (VMRC, unpublished data, 1995). This decline in gear
designed to target peeler crabs has apparently been redirected to the use of peeler pots, which
have been increasing.
Recreational Fisheries
Recreational gears include baited hand lines, mesh rings, collapsible traps, crab pots,
trotlines and dip nets. The Maryland General Assembly is considering a bill during the 1997
Session that would require recreational crabbers to purchase a license, though a license would not
be required to recreationally crab with handlines, dipnets, or crab pots from private property.
Revenues would fund an extensive survey of the recreational crab fishery. From 1989 to 1993,
Maryland required a license for noncommercial crabbers to harvest more than one bushel per day
and no license was required to harvest up to one bushel per day. Noncommercial license-holders
could not sell their catch but were permitted to use more gear than unlicensed sport crabbers. In
1993, 15,378 licenses were issued for noncommercial recreational crabbing in Maryland, more
than double the number of licensed commercial crabbers (6,489). Reported landings by licensed
noncommercial crabbers in 1993 totaled 6.1 million pounds. Maryland surveyed licensed and
unlicensed recreational crabbers in 1990 and estimated 500,000 recreational crabbers made 2.5
million trips and harvested approximately 11 million pounds of crabs (Stagg et al., 1992). Prior to
the 1990 survey, Maryland contracted the National Marine Fisheries Service (NMFS) to include
crabbing questions in the Marine Recreational Fishery Statistics Survey (MRFSS) during 1983
and 1988 (Table 2). The 1990 survey and the two MRFSS surveys were a combination of access
intercept (where crabbers are interviewed in the field) and random telephone surveys. Estimates
from the 1990 survey were calculated differently and may not be comparable to previous surveys.
Table 2. Results of recreational crabbing surveys in Maryland.
Year/Survey
1983/MRFSS
1988/MRFSS
1990/MDNR
Number of
Participants
500,000
Number of Recreational
Crabbing Trips
5.1 million
3.6 million
2.5 million
Recreational Harvest
41.2 million pounds
21.5 million pounds
11.5 million pounds
Historical estimates of recreational harvest in Virginia are not available. A recreational
crab pot license was adopted in Virginia in 1993 which allows the use of up to five crab pots and
unlimited harvest for noncommercial purposes. Recreational crab licenses may also be purchased
for trotlines and one crab pound per person. Licensed recreational crabbers are required to report
their catch to VMRC. Numbers of recreational crab licenses issued in Virginia from 1993 to 1996
are given in Table 3 (Figure 10 and 12; VMRC data). In addition to licensed recreational crab pot
activity, anyone can use two crab pots in Virginia tidal waters with no license to take as much as
one bushel of hard crabs and two dozen peeler crabs per day.
Background 13
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Table 3. Recreational crab licenses issued in Virginia, 1993 to 1996 (VMRC unpublished data).
Year
1993
1994
1995
1996
Crab pot license
361
394
418
383
Trotline license
57
57
Crab trap (pound) license
55
89
Stock Status
Abundance
Blue crab landings can widely fluctuate with changes in market conditions as well as
changes in resource abundance. Crab abundance may, therefore, not always be adequately
indicated by the level of landings. In lieu of fishery-dependent based assessments of resource
conditions, fishery researchers have increasingly relied on data obtained from surveys independent
of the fishery to monitor the resource. Fishery-independent surveys have been used to monitor the
Chesapeake Bay blue crab population since 1956. The surveys use the same sampling protocol
and effort is relatively consistent from year to year.
Virginia Trawl Survey
The longest-running survey for blue crabs in Chesapeake Bay is the Virginia trawl survey
(VIMS/W&M data, 1955 to present). The survey is conducted in the James, York, and
Rappahannock Rivers and Chesapeake Bay by dragging a trawl net. The survey has been
conducted annually from April through November, since 1955. An index of crab abundance,
expressed as the number of crabs caught per tow, is generated annually. Indices are generated by
life-history stage from different segments of the data. For example, the adult female index is based
on trawls during late summer and fall months. Effort in the Virginia trawl survey changed when
the gear was made more efficient in 1972 (a tickler chain was added). To correct for this and
make data from the two gear-types comparable, gear comparisons were used to generate a
conversion factor.
Preliminary analysis of survey indices corrected for gear changes over time tracks what
may be a long-term shift in the blue crab stock (Lipcius, unpublished). From 1956 to 1970,
juvenile blue crab abundance in Virginia was high and fell in the early 1970s. Since 1975, juvenile
crab abundance has shown a gradual and increasing trend back to pre-1970 levels (Lipcius,
unpublished). Scientists from Virginia speculate that this trend in blue crab abundance is
correlated with damage to lower Bay SAV habitat and thin-shelled clams (Macoma spp. and Mya
arenaria), which blue crabs prey on, when Tropical Storm Agnes affected the region in 1972
(Lipcius et a/., 1995). Increasing juvenile crab abundance in Virginia appears to track recovery of
lower Bay SAV beds in the years after Agnes. Adult female abundance from 1955 to 1970 in
Virginia followed the same increasing trend as juvenile crabs and also declined after 1970.
14 Background
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However, indices have shown no increasing trend since 1972 and adult female abundance has
remained low through 1995 (Lipcius et al., 1995). Lipcius et al. (1995) suggest either intense
natural mortality or fishing pressure is preventing crabs from entering the spawning stock. Catch
statistics for the Virginia commercial dredge fishery, which harvests primarily mature females,
also show a decline in winter harvests after 1972 (Figure 13a). When commercial dredge landings
are compared with adult female indices from Virginia's trawl survey, they correlate highly (Figure
13b). The winter dredge fishery is preceded by the fall crab pot fishery in Maryland and Virginia,
which also harvests primarily mature females as they migrate down the Bay to overwintering sites
(MDNR unpublished data, 1981 to 1995; VMRC unpublished data, 1993). Declining harvest by
the winter dredge fishery (Figure 13a), despite increased effort (Figure 11), may be evidence that
females are not surviving to complete their migration down the Bay, possibly due to earlier
harvest in summer and fall, or that spawning stock abundance is at a lower level since the passage
of Tropical Storm Agnes (Lipcius, unpublished).
Maryland Trawl Survey
A trawl survey was also initiated in Maryland in 1975 (MDNR unpublished data, 1975 to
1995). The Maryland trawl survey samples lower portions of the Chester, Choptank, and Patuxent
Rivers, Eastern Bay, and Tangier and Pocomoke Sounds. Abundance patterns from Maryland's
trawl survey, which is conducted May through October, often differ from Virginia. Survey indices
in Maryland indicate that adult blue crab abundance (>119mm or 4.8 inches carapace width) was
relatively high in 1977, low from 1978-1982, and was relatively high from 1983 to 1987. Since
1987 (1988-1995), crab abundance in Maryland has been moderate with the exception of 1992,
which was low. Abundance of juvenile crabs (<60mm carapace width or <2.4 inches) in Maryland
was low from 1978 to 1982 and fluctuated between high and moderate levels from 1983 to 1994,
with the exception of 1987, which was low. Juvenile abundance in 1995 was low overall,
however, surveys in late 1995 and the first two months in 1996 found unusually high numbers of
juveniles (MDNR unpublished data, 1977 to 1996). There is speculation that the extraordinarily
high abundance of juvenile crabs in several coastal states during this period was the result of
tropical storms and hurricanes in the Atlantic which influenced nearshore ocean currents
near shore.
Chesapeake Bay Winter Dredge Survey
A third survey, the Chesapeake Bay Winter Dredge Survey, randomly samples the entire
Chesapeake Bay and tributaries during winter months when crabs are inactive. A commercial-style
dredge is used to dig into the Bay sediments where crabs overwinter. Because the dredge survey
monitors the entire Bay, it provides an important and consistent way to measure Bay trends since
it uses one method baywide. The Virginia and Maryland trawl surveys provide additional
information on regional trends. However, the dredge survey only began in 1990, and the short
data set does not show long-term trends in crab abundance. The blue crab population in
Chesapeake Bay was estimated from the winter dredge survey by Rothschild and Sharov (1996).
Numbers of crabs per meter sampled were extrapolated to estimate the crab population for the
entire area of the Bay. The total population (all sizes and sexes) during the winter of 1995 was
estimated to be 770 million crabs, of which 336 million were crabs one-year-old or greater
Background 15
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(>60mm carapace width; or >2.4 inches). These estimates are thought to be conservative when
compared with total baywide landings.
Exploitation rates calculated from Virginia trawl survey data and crab pot survey data
from Calvert Cliffs, Maryland (Abbe and Stagg, 1996), have also been used to back-calculate
estimates of population size (Rugolo etal., unpublished). In 1995, the population (reported as
biomass) of crabs greater than 60 mm (2.4 inches) was estimated to be between 400.81 million
crabs (169.43 million pounds) and 438.14 million crabs (185.12 million pounds). Since 1968, the
average estimated population size from the same two surveys was 420.9 million crabs (181.10
million pounds) to 467.62 million crabs (201.91 million pounds) and the range was 236.74 million
crabs (97.98 million pounds) to 678.65 million crabs (288.52 million pounds).
Mortality and Exploitation
Fishing mortality (F) is a measure of the rate at which blue crabs are removed from the
population by the fishing activities of man. If F is constant over time, harvest will be greater
during times of high abundance and less during times of low abundance. Generally, F is not
directly measured. First, total mortality (Z) is evaluated and then natural mortality (M) is
subtracted, leaving F (F=Z-M). Estimates of mortality are derived from evaluating changes in
abundance over time, as measured by fishery-independent surveys. Fishing mortality may also be
estimated from commercial landings. Exploitation (u) is related to estimates of mortality and is the
fraction of a population that is removed by harvest (accounting for any concurrent natural
mortality) over the course of a year (Ricker, 1975). Exploitation and rates of mortality may also
be expressed as a percentage of the population (non-technical discussion in Wallace et al., 1994).
Blue crab fishing mortality is estimated using various surveys in Chesapeake Bay.
Rothschild et al, (1992) analyzed Baywide winter dredge survey data and commercial harvest.
Estimated values of M ranged between 0.17 and 0.37 and F was as high as 4.5 (exploitation =
92% to 95% for given range of M). Rothshild et al. considered estimates of F between 1.6 and
2.0 likely (exploitation = 70% and 82% for given ranges of M and F). Utilizing the same data,
Volstad etal. (1994) calculated exploitation rates of 50% to 92% for crabs over 2 inches (50mm)
carapace length. Neither Rothschild or Volstad included commercial soft and peeler crab harvest
or recreational harvest, which would increase estimates of F and u. Analysis of Maryland summer
trawl survey data by Casey et al. (1991) estimated M between 0.1 and 0.5 and F between 1.3 and
2.0 (exploitation = 70% to 73%). The above estimates of mortality were made by evaluating
changes in abundance between presumed year classes (based on observed size classes) and may be
biased where age of the animal is not well defined.
Chesapeake Bay Stock Assessment
In 1996, the Chesapeake Bay Stock Assessment Committee (CBSAC), of the Chesapeake
Bay Program, conducted a baywide stock assessment for blue crab (Rugolo et al., unpublished).
Forty years of data from four fishery-independent surveys were analyzed; these include the
Maryland Trawl Survey, the Virginia Trawl Survey, the Baywide Winter Dredge Survey, and a
crab pot survey off Calvert Cliffs, MD (1968-1995; Abbe and Stagg, 1996).
16 Background
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Mortality
Fishing mortality rates were calculated based on crab length frequencies from fishery-
independent surveys (length measured from spine to spine). Length-based estimates for Z ranged
from 0.875 to 1.54 (A = 58% to 78%) over the 40-year data series. Subtracting M (0.375; 20%
to 25% annually when Z = 0.88 to 1.54) provided estimates of fishing mortality rates (F). Since
1956, fishing mortality rates appear to have varied without trend (range: 0.50-1.16; exploitation
rate = 33%-59%), despite a five-fold rise in fishing effort in the commercial fishery since 1945. A
slight increase in fishing mortality was noted in the early 1990s, however, there was a drop in
1995. Fishing mortality rates in recent years (1990 to 1996) have been around 0.9 to 1.0
(exploitation rate = 51% to 54%).
The CBSAC stock assessment found no indications of recruitment overfishing. Indices of
abundance from the four surveys were expressed as the number of crabs caught per unit of effort
(i.e. crabs per trawl, crabs per square meter sampled). Indices of abundance from surveys indicate
that the blue crab population was high in the late 1980's through 1991 and, since 1991, has
returned to levels typical during years prior to the 1980s. Juvenile recruitment indices in the 1990s
have been increasing, further indicating that recruitment overfishing is not occurring. Given the
steady state of exploitation and recruitment for 40 years, it appears that the blue crab has been
able to withstand annual exploitation rates up to 59% (F = 1.16).
Threshold Limit for Fishing Mortality
The blue crab fishery was characterized by the CBSAC stock assessment as fully
exploited. This description is based on a threshold limit fishing mortality rate that allows for at
least 10% of the spawning stock (measured by weight) to escape the fishery to reproduce (F10%;
measured as 10% of the spawning stock in the absence of a fishery). The target rate should be set
at a safer level. The selected FIOS of 1.2 (exploitation rate = 60%) should be a maximum limit.
Results indicate that fishing mortality rates for blue crab in Chesapeake Bay have remained at or
below the estimate of F10% .
Stock assessment is an analytical process that incorporates understanding of the life
history of the species and historical performance of the fisheries. The status of "fully exploited"
includes the assumption that the maximum attainable age of the blue crab species in the absence of
fishing pressure is eight years and that female crabs cease spawning at age six years (based on
present estimates of reproductive ability). Changes to these variables produce results that are less
protective of the resource. Selection of the maximum age of eight for blue crab produces higher
estimates of fishing mortality rates at F10%. The selection of age eight is based on the results of a
historical blue crab tagging study (McConaugha, 1991; 1993) which resulted in several recoveries
of crabs age five and six-years-old and one recovery in 1995 corresponding to a 7.5 year-old crab.
Calculations based on previous estimates of maximum age at six and four years produced higher
estimates of threshold mortality rates at F10%. These previous estimates would produce
management practices that are less protective of the resource. Although corresponding estimates
of actual fishing mortality rates were also higher, the assumption of a shorter life span implied that
the stock could withstand a higher level of fishing mortality than had been measured in the recent
past.
Background 17
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Fishing Effort and Gear Efficiency
Since 1945, deployment of more gear has not resulted in any proportional increase in
fishing exploitation rates. This has been explained by the catchability (q) of the crab pot (the
ability of the gear to catch crabs or the catch efficiency of the gear). A crab pot is capable of
attracting crabs presumably within some constant radius (i.e. crabs beyond a certain distance will
not be attracted to the bait) and, of the crabs within range of the gear, some will not be attracted
to it for various reasons. Crab pots and trotlines are static gears which require that crabs approach
the gear voluntarily (as opposed to active gears such as trawls and dredges, which actively
capture animals and prevent them from escaping). Some crabs may choose not to approach a pot
or trotline because they are not searching for food or they may avoid pots saturated with crabs,
which can be cannibalistic. Crab pots within close proximity may compete with each other. Also, a
certain portion of crabs may be able to escape the gear. Small-scale studies in Maryland, where
blue crabs were marked and left abandoned in pots, found that some crabs were able to find their
way out of the gear over time, depending on the time of year (Casey and Wesche, 1981).
Catchability (q) measures the average portion of a fish stock that a unit of gear (i.e. one
crab pot) is capable of catching (i.e. the mortality rate, F, per unit of fishing effort) and should not
be confused with CPUE. CPUE measures the number or weight (biomass) of crabs caught per
unit of gear (for example, Figure 7 is expressed in pounds per pot). CPUE may be influenced by
changes in crab abundance (for example, higher abundance means more crabs are available to be
caught); whereas, catchability measures the portion of a stock that will be captured, regardless of
abundance. CPUE can also be influenced by catchability. Increased effort in a fishery can affect
catchability in one of three ways: 1) catchability may remain the same and more gear will result in
a greater total harvest; 2) catchability may increase as the probability of crabs encountering the
gear increases, also resulting in a greater total harvest; or 3) catchability may decrease as the gear
competes with each other to catch the same portion of crabs, resulting in stable harvest in spite of
increased effort. In scenario one, CPUE would only fluctuate as a result of changes in stock
abundance and could be used as an indicator of stock health. In the second scenario, CPUE may
increase regardless of stock abundance and can give a false indication that the stock is healthy. In
scenario three, CPUE may decrease and give a false indication that the stock is declining. The
CBSAC stock assessment estimated nominal fishing effort in the Chesapeake Bay blue crab
fishery. Nominal fishing effort (f) is the unit of effort measured in time (days fished) and number
of gear units. Since 1945, nominal fishing effort has risen fivefold; whereas, catchability (q) has
declined. This has resulted in decreased CPUE (Figure 7) and the steady state of fishing mortality
(F).
Economic Implications
Although the results of the stock assessment are positive for the current status of the blue
crab resource, they do indicate that the resource is not being harvested in the most economical
manner. Prior to 1994, blue crab fisheries in Maryland and Virginia were open access and had
only limited obstacles to obtaining a license to participate in the commercial harvest of blue crabs.
Rising numbers of participants since the 1940s has resulted in increased competition between
participants and overcapitalization of the commercial fishery. As competition for the same number
of crabs has intensified, the catchability of the gear has decreased and CPUE declined. In its
current state, participants in the fishery are deploying more gear and working harder to catch an
equivalent portion of the available stock.
18 Background
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Problems and Concerns
Fishing Pressure
Maximum Sustainable Yield (MSY) is defined by Ricker (1975) as the largest average
catch or yield that can continuously be taken from a stock under existing environmental
conditions. In effect, it is the greatest poundage of blue crabs that can be removed from the bay
without reducing the capacity for the crabs to replenish the population to the same level for
harvest in future years. When MSY is exceeded and stock replenishment is at risk, the resource is
said to be recruitment overfished. Larkin (1977) argued MSY is not attainable on a sustainable
basis. Often, MSY is modified for optimum yield (OY) by factoring in economic, social or
ecological issues and OY is frequently used as justification for harvest exceeding MSY (National
Academy Press, 1994). The collapse of certain fish stocks has been attributed, in part, by Ludwig
et al. (1993) to management based on MSY estimates.
In addition to Ricker's (1975) definition of MSY, he notes that for species with fluctuating
recruitment, the MSY is dependent on yearly abundance. The size of the blue crab stock is initially
controlled by entry and settlement of blue crab postlarvae in nursery habitats (i.e., the survivors of
the larval phase) and abundance can fluctuate annually. To prevent recruitment overfishing of
stocks with variable abundance, as has occurred in many other exploited species (Holmes, 1994),
it may be necessary to take fewer fish in some years. For managers to apply such a method,
abundance must be predicted with confidence prior to the harvest season. Given the past failures
of MSY (Ludwig et a/., 1993; Larkin, 1977) and the scientific uncertainty of some parameters
used in the current stock assessment of blue crab (Rugolo et a/., unpublished), a conservative
approach to blue crab management in Chesapeake Bay is recommended.
Growth Overfishing versus Recruitment Overfishing
Two types of overfishing, growth and recruitment overfishing, are defined by this
management plan. Growth overfishing occurs when the losses in weight (biomass) from harvest
and natural mortality exceed the gain in weight due to reproduction and growth. Hence, there is a
net loss of biomass from one year to the next (NMFS, 1993) which is characterized by a
decreasing proportion of older and larger individuals in the catch. Growth overfishing may
continue without any visible effect on the number of individuals in a stock (i.e. reproduction
remains high enough to replace individuals removed by the fishery); however, if fishing pressure is
too high, it can result in recruitment overfishing. Recruitment overfishing is the rate of fishing
above which recruitment to the exploitable stock is reduced and is characterized by a reduced
spawning stock and generally very low production of young year after year (NMFS, 1993).
The decline in the blue crab population in Chesapeake Bay in the early 1990s, along with
increased fishing effort and decreased CPUE in the commercial fishery since 1945, were believed
to be symptomatic of a stock in the process of being recruitment overfished. However, the decline
in CPUE occurred between 1945 and 1970 and fishing mortality rates since 1945 vary within a
relatively constant range and appear to be stable (Rugolo et al., unpublished). When long-term
trends were analyzed, blue crab abundance was unusually high in the 1980s and the reported
decline from 1990 to 1995 was a return to average levels of abundance. Abundance of juvenile
crabs during this same time period has been increasing and indicates that recruitment overfishing
Background 19
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is not occurring. In the case of blue crabs, greater effort has produced stable landings and no
increase in the portion of the stock being removed by the fishery (fishing mortality).
In addition to threshold harvest limits (F10%), the level of F at which the greatest yield per
recruit is seen from the fishery (F^ was estimated for Chesapeake Bay (Rugolo et al.,
unpublished). Yield per recruit refers to the size or weight per crab harvested and larger crabs
generate a higher yield per recruit. Current levels of F between 0.8 and 1.0 exceed the estimated
Fmax of 0.64. Currently, there is not consensus among Bay scientists surrounding the implications
of growth overfishing. The debate is complex and combines the concerns of economic stability of
the fishery and the biological well-being of the resource. A recent analysis by Abbe and Stagg
(1996) cites growth overfishing as the probable cause for an observed and gradual decline in the
mean size of male crabs 5 inches and greater from 1968 to 1995. Although the decline is reported
to be statistically significant (p=0.001), there is also a high level of variation in mean size over
time (r2=0.356). Given the variation, mean lengths of legal size male crabs in this study decreased
by approximately 10 mm (0.4 inches) over the time period. Rugolo etal. (unpublished)
acknowledge that, while current levels of F are in excess of FmM , evidence of growth overfishing
(i.e. decreasing size) should be coupled with an increase in fishing mortality rates over time.
Results of the baywide stock assessment did not detect any increasing trend in F from 1956 to
1990 and the rise in F seen between 1991 to 1994 did not exceed F10S. Furthermore, from a
management perspective, the present level of effort and participation in the fishery would have to
be reduced to levels measured in 1956, or less than one-sixth of current levels, before an increased
yield from the fishery could be obtained.
From a risk-averse perspective, there is concern that current levels of F not only exceed
Fmax' but are approaching the recruitment overfishing threshold (F10%). Measured attempts to scale
down effort could provide a buffer against recruitment overfishing, in addition to improving the
performance of the fishery. Because there is no current danger of stock collapse at present levels
of fishing mortality, this could be done gradually, over time, and in consultation with the industry.
Adopting a target fishing mortality rate such as Fnax as a reference point would move the fishery
further away from the recruitment overfishing level, providing a buffer for errors in estimates of
limiting levels of exploitation, while simultaneously providing yield per recruit benefits. The
debate surrounding growth overfishing is constructive and the issue will continue to be revisited in
upcoming years as the baywide stock assessment is updated and additional studies become
available.
Target Setting Task Force
In addition to the CBS AC stock assessment, the Chesapeake Bay Program (CBP) formed
a Target Setting Task Force to develop methods for measuring the progress of efforts to protect,
restore, and enhance selected Bay species. Targets can help define the status of the stock and its
probable status under alternative management strategies. Blue crab targeting efforts focus on an
exploration of two areas: environmental factors that affect stock size and recruitment; and the
spatial and temporal patterns of blue crab by life history stage. The results are anticipated to
provide indices and life history models that are region-specific and sex-specific and explore stock-
recruitment relationships. The target setting exercise for blue crab should be complete in 1998 and
will provide managers with another tool to monitor stock status trends and respond with
management measures which are effective for protecting the resource and the fishery.
20 Background
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Female Harvest
The number of crabs recruiting to Chesapeake Bay in any given year relies, in part, on the
size of the spawning stock from which the young originated. The spawning stock includes all
females that survive natural and fishing mortality to reproduce. It is not limited to those crabs
possessing an egg mass, nor to those mated females that do not show eggs. Except during
molting, when crabs are vulnerable to predation, juvenile females larger than 80-100 mm in
carapace width (approximately 3.2-3.9 inches) suffer relatively low natural mortality and should
reproduce if they are not removed by the fisheries.
Portions of the potential spawning stock are removed from the population by different
segments of the fishery. When regulating harvest and effort, due consideration should be given to
the fisheries and their respective harvest of potential spawning stock. The crab pot fishery lands
the greatest portion of female hard crabs (MDNR unpublished data, 1981 to 1995; VMRC
unpublished data, 1993). The extent of female harvest by the soft and peeler fishery is unknown.
Male Harvest
Insemination rates of female crabs and the amount of sperm they receive from male crabs
during mating may be dependent on the abundance and size of male crabs in the population.
Insemination rate is the proportion of females in the population that successfully mate during their
terminal molt to maturity. The sperm that a female receives at the time of mating, which is during
the maturation molt, is stored for many months in paired storage vesicles (spermathecae) until
they produce broods of eggs during the spawning season. If female blue crabs mate only one time
and with only one male, as published by Van Engel (1958), the amount of sperm she receives
must last for her lifetime of brood production. If females fail to find a suitable mate at the time
they are ready to mate, they are thought to be unable to contribute to the spawning stock. In
addition, a small male may not be able to transfer enough sperm for the female to fertilize all of
the eggs she is capable of producing.
Research indicates that fishing pressure has probably not affected insemination rates of
female blue crabs, which are generally high (>95%) in Maryland and Virginia portions of
Chesapeake Bay, South Carolina, and Florida (Wenner, 1989; Jivoff, 1995). However, in the
upper Chesapeake Bay, the amount of sperm that mated females receive is highly variable among
individuals and among years, with large proportions of newly mated females having spermathecae
which were only partially full (range 20-100% full) during 1990 to 1994 (Jivoff, 1995). Controlled
laboratory and field experiments show that variation in the amount of sperm received by a female
blue crab is regulated by male size, sex ratio, and short-term mating history (Jivoff, 1995). Small
males transfer less sperm than large males, and females receive less sperm when small males are
over-represented in mating pairs (Jivoff, 1995; in press). More sperm is transferred to females in
crab stocks with a sex ratio dominated by males than when males are proportionately less
abundant (Jivoff, 1995). Recently mated males are less willing to mate again and, when they do
re-mate, they transfer less sperm than males that have not mated recently (Jivoff, 1995; in press).
Exploitation of male crabs in other fisheries has demonstrated effects on the amount of sperm that
females receive (Paul and Paul, 1992; Sainte-Marie and Lovrich, 1994; Sainte-Marie el a/., 1995).
Consequently, it is important for managers to consider not only the impact of harvesting mature
female crabs, but, also, the influence on males in the population. Male reproductive capacity can
have a significant effect on the lifetime reproductive success of females.
Background 2 \
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Wasteful Harvesting Practices
Harvesting practices are identified as wasteful when they decrease economic yield from
the fishery or make crabs unavailable for future harvest. For example, buckrams, which are crabs
that have recently shed but have not yet grown into their new shell, are light weight and yield less
meat than fully developed hard crabs. Small size limits in the soft and peeler fishery results in a
greater number of crabs harvested per pound of meat. Small crabs contain less meat and, although
they have high market value, their harvest may not maximize yield from the resource. The
consumer preference for large softshell crabs shipped into Maryland demonstrates a market
demand for large softshell crabs (Uphoffel a/., 1993). Increased size limits could make
Chesapeake Bay's product more competitive.
Blue crabs are cannibalistic predators and sublegal-sized crabs retained in crab pots with
larger crabs experience high mortality rates (Eldridge et al., 1979). Cull rings installed in the mesh
of a crab pot provide a circular opening that allows undersized crabs to escape. In South Carolina,
Eldridge et al. (1979) tested 2.4 inches and 2.5 inches diameter cull rings in standard crab pots for
small crab escape efficiency. Pots with two 2.4 inches rings reduced sublegal crab catch by 62%
and pots with two 2.5 inches rings reduced sublegal catch by 76% when compared with no cull
rings. Raynie and Casey (1992) investigated the use of one to three cull rings, 2.25 inches in
diameter, in crab pots for practical use in Chesapeake Bay. No legal-sized crabs escaped through
the rings and pots retained 83%-89% less sublegal crabs than pots with no cull rings. These
results are slightly higher than Eldridge et al. (1979) found in South Carolina. The South Carolina
study employed greater numbers of pots and is considered more statistically sound.
Commercial watermen have expressed concern for the potential loss of small peeler crabs
and mature females that are legal to harvest. Virginia investigated the loss of small, mature
females from cull rings and found that a cull ring with a 2 3/16 inches diameter allowed only
minimal losses (VMRC unpublished data, 1995). Self-culling crab pots reduce injury to sublegal
crabs and save time because crabs do not need to be culled by hand.
Crab pots lost to storms or left abandoned at the end of the fishing season, often called
ghost pots, are attractive refuge sites for blue crabs. Crabs and fish trapped inside abandoned pots
die and attract other animals into the pots (Guillory, 1993). This process of self-baiting is a
problem in many other pot fisheries including lobster, king crab, snow crab and black cod. As a
cannibalistic species, blue crabs may be attracted by dying crabs impounded in abandoned traps.
In Louisiana, Guillory (1993) found 55% mortality of impounded crabs. A similar study by Casey
and Wesche (1981) examined 40 unbaked pots on a weekly basis in Sinepuxent Bay, Maryland,
from July through December. A total of 1,033 crabs were impounded; 33% of the impounded
crabs were unable to escape and subsequently died. Pots abandoned during winter months in
Chincoteague Bay, Maryland, caught fewer crabs than pots abandoned during warmer months,
but mortality increased to 100% in the winter months. Such high mortality may have been due to
decreased water temperature and a crab's inability to bury in sediments (Casey and Daugherty,
1989).
Watermen interviewed from the Chesapeake Bay region estimated 10-30% of pots are lost
each year (Casey, 1990). The lobster fishery in New England (New England Fish. Mgt. Counc.,
1983) proposed developing biodegradable escape panels. Casey (1990, 1992) studied materials
for degradability in Chesapeake Bay. Escape panels made of jute decayed within two months. This
may not be accepted by watermen who would have to replace them frequently throughout a
22 Background
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season. Cotton twine escape panels were unreliable and decay rates varied. Materials that
degraded in six to nine months also proved impractical. Fouling tended to clog escape vents as
panels degraded. Other options included nongalvanized wire mesh over a portion of the pot or
burning off galvanizing with a torch in a section chosen for escape. Nongalvanized wire rusts and
weakens over time. Variability in the degradation times of escape vent materials under different
environmental conditions needs thorough examination before a recommendation can be made.
International Trade and Implications for the Chesapeake Bay
The United States is one of the largest exporters of crabs and crab products worldwide in
terms of dollar value. In 1994, United States exports of crabs and crab products totaled $347
million (NMFS, 1995). Chesapeake Bay blue crab harvest has accounted for over 50% of national
landings since the 1970's (Orth and van Montfrans, 1990), though growing crab fisheries in the
South Atlantic and Gulf states have been increasing their contribution to the national harvest.
Crab fisheries are developing worldwide, particularly for crabs of the genus Portunus, which are
similar in appearance and marketability to blue crab (Petrocci and Lipton, 1994).
In addition to being one of the world's largest exporters of crabs, the United States was
the second largest importer of crab and crab products in 1993, outranked only by Japan (Petrocci
and Lipton, 1994). Venezuala, Mexico, Indonesia, Thailand, South Korea, and China are the
largest source of crabs imported to the U.S. . Imports in 1993 were worth over $150 million
(Petrocci and Lipton, 1994). As more countries develop crab fisheries and processing techniques,
the crab supply worldwide will continue to grow. From 1982 to 1991, worldwide landings of crab
species increased by almost 60%. Petrocci and Lipton (1994) provided recommendations for the
Chesapeake Bay product to remain competitive in the domestic and international market. In
particular, they stressed the importance of distinguishing the Chesapeake product as one of
superior quality and taste. The development of value-added products that stimulate and maintain
consumers' desire for the region's product was also suggested.
Petrocci and Lipton (1994) assessed Asian crab fisheries and production and predicted
Asia would grow in international importance for crab harvest and productivity. Asian resources
are reportedly abundant and underutilized, which makes the product inexpensive. Worldwide
landings of Portunus have increased from 56,400 metric tons (mt) in 1982 to 227,100 metric tons
in 1991. Worldwide landings of blue crab increased during the same time period (99,900 mt to
111,700 mt), though not as rapidly as for Portunus. However, the fisheries for Portunus include
numerous species; whereas, the blue crab fisheries harvest a single species. Petrocci and Lipton
(1994) stressed the importance of acknowledging the potential for competition from abroad and
the relationship between the long-term health of the resource and the ability to compete in an
international market. In the Chesapeake region, Petrocci and Lipton warned of the effects of
overcapitalization, high levels of fishing pressure, and competition that drive the product price up.
Limited access to the fishery was recommended to prevent overcapitalization, increase
productivity, and lower the cost of harvesting crabs. To remain competitive in the global market,
managers and the industry are urged to focus on the health of the resource, rather than short-term
availability from one season to the next. Petrocci and Lipton's (1994) conclusion is in accordance
with the goal of this management plan and the recommendation that limited entry and stabilization
of fishing effort be implemented Baywide as a management strategy.
Background 23
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Parasites and Disease
Diseases and infections in the blue crab population can bring about wide and varied
effects, both actual and perceived, on the blue crab and its industry. Even the perception of
disease and pathogens, once shared with the public, can have considerable effects on the industry
and on management. A variety of pathogens can affect crustaceans, including viruses, bacteria,
fungi, protozoans and helminths. Some cause unattractive necrotic lesions on the shell or black
pigmentation in the meat, rendering affected crabs unmarketable. Other pathogens may reduce
fecundity, while still others are documented to cause significant mortalities. The parasitic
dinoflagellate, Hematodiniutn perezi, was first described by Newman and Johnson (1975) from
blue crabs in coastal areas of North Carolina, Georgia and Florida. In recent years, the parasite
has been detected in blue crabs from coastal bays of Maryland and Virginia (Messick, 1994) and
crab mortalities have been associated with the parasite.
The relationship between stress and disease is a well documented phenomenon.
Sindermann (1989) found that the occurrence of disease was higher in stressed populations. In a
number of instances, degraded water quality has been implicated in blue crab disease (Engel and
Noga, 1989; McKenna etal, 1990). Because many infections are contagious to other crabs and
may be an indication of stress in a population, existing diseases and parasites, such as
Hematodinium, should be actively monitored in both Maryland and Virginia.
Water Quality
Worldwide, estuaries are experiencing water quality problems as a result of human
activities in coastal areas. Chesapeake Bay, one of the world's largest estuaries, has experienced
deterioration of water quality from nutrient enrichment, sediment inputs, and high levels of
contaminants. Declines in living resources are attributed to degradation of water quality (Horton
and Eichbaum, 1991).
Excess Nutrients and Anoxia
High levels of nitrogen and phosphorus in the Bay's mainstem and tributaries lead to
favorable conditions for explosive algae blooms. Phytoplankton in the water column are so
abundant during such blooms that they block sunlight to underwater Bay grasses and plankton
deeper in the water column. Grasses and plankton subsequently die and decompose. This
decomposition uses oxygen at an accelerated rate, causing water oxygen levels to drop. Lowered
dissolved oxygen inhibits Bay grass respiration and limits the amount of area suitable for many
forms of aquatic life. Anoxic (no oxygen) and hypoxic (low oxygen) conditions kill benthic food
organisms.
During the months of May to September, deeper waters of the mid-Bay mainstem, from
Baltimore to the mouth of the Potomac River, are subject to anoxic conditions (Officer et al.,
1984; Taft et al., 1980; see Figure 3). The anoxic portion of the Bay varies from year to year.
Although low dissolved oxygen levels are, in part, a result of natural conditions in the Bay, the
anoxic portion has been increasing in size and duration in recent years. Dissolved oxygen
depletion was first documented as hypoxic areas, or areas of reduced oxygen content. Over the
years hypoxic conditions have worsened to anoxic conditions (Officer et al., 1984) Historically,
the affected area was limited to a narrow strip of the deep channel in the Bay. In some years,
anoxic conditions now cover a much wider area, with fringes of hypoxia stretching across almost
24 Background
-------
the width of the Bay and down to the Bay mouth (Officer et al., 1984). Cross-current winds and
low pressure storms often push anoxic water into shallow areas.
As winter approaches, decomposition of organic matter slows down and oxygen supplies
are replenished with greater mixing of fresh and saltwater layers (diminished halocline) in the Bay
mainstem. The depletion of filter feeders in the Bay, particularly oysters, may aggravate the
situation. Oysters filter feed on phytoplankton suspended in the water column, and, unlike other
phytoplankton feeders, overwinter in the Bay. Spring warming stimulates feeding early in the
season. Today, a large portion of the spring phytoplankton bloom goes ungrazed (Newell, 1988),
adding to organic accumulations later in the season and potentially further contributing to anoxia.
Toxics
Blue crabs that overwinter in sediments are exposed to accumulations of toxic substances.
Their preference for feeding on bottom-dwelling organisms, such as filter feeding bivalves, also
make them likely candidates for toxics bioaccumulation. However, because blue crabs are
migratory and have a short life span, toxic accumulation has not been a problem. Crabs examined
in the two most polluted areas of Chesapeake Bay, the Elizabeth River (Norfolk, VA) and
Patapsco River's Baltimore Harbor (MD), were highly tolerant of toxic environments. Minimum
amounts of contaminants were found in muscle tissue; higher levels of some contaminants were
accumulated in the hepatopancreas (Garreis and Murphy, 1986). Blue crab larvae may be sensitive
to contaminants in the water. Sublethal doses of toxics slow larval development (Epifanio, 1984).
Van Heukelem (1991) summarized literature on contaminants to blue crabs. Contaminants
included petroleum hydrocarbons, polynuclear aromatic hydrocarbons, polychlorinated biphenyls,
kepone, mirex, malathion, halogenated compounds, chlorine and chlorine-produced oxidants, and
heavy metals including cadmium, chromium and mercury. No literature was found on the effects
of arsenic, copper, lead, mercury, nickel or zinc.
Submerged Aquatic Vegetation
One of the major factors contributing to the high productivity of Chesapeake Bay has been
the historical abundance of submerged aquatic vegetation (SAV, also called Bay grasses). SAV
provides important habitat for settling postlarvae (Orth and van Montfrans, 1987) and molting
crabs (Ryer et al., 1990). SAV growth is restricted to shallow water areas and is limited by light
availability. Therefore, water quality is of utmost importance for successful re-establishment of
SAV.
Nutrient and sediment effects
A Baywide decline of all SAV species in Chesapeake Bay occurred in the late 1960's and
early 1970's (Orth and Moore, 1983; 1984). The decline was attributed to increasing amounts of
nutrients and sediments in the Bay (Kemp el al., 1983; Twilley et al., 1985). Soil runoff increases
as the wetlands and forests are lost to development and agriculture. Without forest or grass
buffers and wetlands, eroded soil and nutrients enter water bodies (Schlesinger, 1991). Nitrogen
and phosphorus from agricultural and urban landscape fertilizers enter the Bay as runoff or as
dissolved ions percolated into groundwater. Atmospheric nitrogen oxide from the burning of
fossil fuels is deposited on the water's surface via rain or dry deposition.
Background 25
-------
Suspended sediments and excess nutrients in the water have impacted SAV in varying
ways, primarily through light-related perturbations. Sediments from surrounding uplands or
resuspended from bottom deposits can severely limit light penetration through water. Nutrients
enhance the growth of phytoplankton in the water column and epiphytic algae that grow on SAV
leaf surfaces. Phytoplankton and epiphytes block light that would normally reach SAV leaves,
reducing photosynthesis. The spectral character of the light may also be changed, placing
additional stress on SAV growth and survival.
Researchers believe that recent efforts to improve water quality, through nutrient input
reductions and managed shoreline development, have influenced the recovery of SAV in
Chesapeake Bay. Although recent restoration efforts have led to an improved status of SAV in
the Bay, there are still only approximately 60,000 acres of SAV in the Bay and its tributaries.
Chesapeake Bay Program scientists estimate that historically 400,000 to 600,000 acres of SAV
might have existed. It is believed that most of the major SAV declines in Chesapeake Bay have
occurred outside the primary settlement and nursery areas for the blue crab (Orth et al., 1995).
However, these vegetated habitats are of such vital importance to maintaining historically high
population abundances of crabs that they should be recognized and preserved (Orth et al., 1996).
Figure 14 shows areas of particular importance to postlarval settlement and juvenile development.
Outside of the primary settlement areas for blue crab postlarvae, SAV beds are also important
refuge sites during molting and soft-shell phases. Figure 15 displays potential SAV habitat for
blue crabs baywide. Baywide, SAV beds are an important component of the Chesapeake Bay
ecosystem and, as such, indirectly impact the blue crab population by supporting communities of
prey items and regulating water quality.
Effects of physical disruption
Human activities in coastal areas and on the water reduce the area of shallow water
available for crabs and SAV and physically disrupt SAV in shallow water habitats. Shoreline
structure, such as bulkheads, revetment and breakwaters, increase wave energy near shore and
reduce shallow water habitat suitable for bay grasses. Grasses sliced at the base by dredging for
commercial fisheries must recover before they can offer refuge to blue crabs. The effects of heavy
crab scrapes dragged through grass beds to collect soft and peeler crabs are unknown. Areas of
high frequency scraping may be scarified the same way high frequency propeller contact scars
grass beds, often resulting in permanent alteration of the habitat (Fonesca et al., 1992). Large
boats are being utilized more by crab scrapers, and the crab scrape fishery is expanding as more
watermen drop out of the oyster fishery and outfit their boats and power rigging for the crab
fishery. The use of power winders to haul scrapes has not been investigated for the potential to
damage SAV habitat. Virginia limits the size of scrapes and prohibits mechanized hauling of crab
scrapes. Hand pulling limits the weight of scrapes that can be hauled. Clam dredging may also
cause local SAV destruction via physical disruption (Hurley, 1991).
26 Background
-------
Chesapeake Bay Program Efforts
Nutrient Reduction*
The 7957 Chesapeake Bay Agreement (Chesapeake Executive Council, 1987), signed by
the jurisdictions of Maryland, Virginia, Pennsylvania, and the District of Columbia, established a
goal of reducing controllable sources of nutrients to the Bay by 40% from 1985 levels by the year
2000. Controllable sources include runoff from agriculture, urban and suburban areas; shoreline
erosion; and point sources such as sewage treatment plants. It was estimated through analysis of
computer models that achieving the 40% reduction goal would reduce anoxic conditions in the
Bay by 20 to 25% in an average year. The same model also estimated that anoxic conditions
would increase by 15 to 20% over a ten-year period if no nutrient reduction occurred. From 1984
to 1992, phosphorus concentrations in the Bay declined by 16% and nitrogen levels held steady
with no decline. Effects of nutrient reduction efforts take several years before results are visible
(Kunishi, 1988) No consistent pattern of improvement in the Bay's dissolved oxygen or a
reduction of algae has been noted to date (CBP, 1995b).
Uncontrollable sources of nutrients not included in the 40% reduction goal, most notably,
atmospheric deposition, add significant amounts of nitrogen to the Bay. Atmospheric nitrogen
deposited directly into the water may account for 10% of the nitrogen load to the Bay.
Furthermore, accounting for atmospheric nitrogen deposition in the entire Bay watershed
increases the estimate to 40%. Nitrogen released to the atmosphere from the burning of fossil
fuels is regulated on the federal level by the Clean Air Act. The federal Act mandated a 2 million
ton reduction in nitrogen oxide emissions by the year 2000, however, it does not establish a cap
for total nitrogen oxide emissions to compensate for future growth and fossil fuel demand. The
Clean Air Act also requires automobiles built after 1993 to have 60% reduced nitrogen oxide
emissions. Although this mandate is expected to reduce nitrogen emissions, the result will be
much less than 60%, due to the growing demand for automobiles and the continued use of
vehicles manufactured prior to 1994. Studies by the Maryland Department of the Environment
and the U.S. Environmental Protection Agency concluded that future growth will cancel out much
of the reduction of atmospheric nitrogen resulting from the Clean Air Act. By the year 2010, the
net result may only be about a 5% reduction.
Minimum Dissolved Oxygen Requirements
Action 6.1.2 of this Plan recommends minimum standards for dissolved oxygen in
Chesapeake Bay waters for blue crabs. Achieving the minimum standards depends on four factors.
1. The Bay jurisdictions should continue to work towards the goal of 40% reduction in
controllable nutrient sources.
2. Without capping nutrient loads, the minimum dissolved oxygen requirements
recommended by this plan can not be maintained. The jurisdictions should continue to
1 Reviewed in: Chesapeake White Paper. 1993. Nutrients and the Chesapeake: Refining the Bay cleanup effort.
Alliance for the Chesapeake Bay. Baltimore, MD; Richmond, VA; Harrisburg, PA.
Background 27
-------
work towards capping nutrient loads to the Bay, once the 40% reduction is accomplished,
as agreed on in 1992 (Chesapeake Executive Council, 1992).
3. The Bay jurisdictions should continue to study the cost and benefits of going beyond the
federal Clean Air Act. The Bay jurisdictions are leaders in resource conservation and have
set major precedents for watershed management. A stronger commitment to reducing
atmospheric pollution would be of great benefit to Chesapeake Bay, set precedent for air
quality as an integral part of watershed management, and provide new leadership for
regional watershed management.
4. The Bay jurisdictions should work cooperatively with outside jurisdictions that impact the
Chesapeake Bay airshed.
A fifth possible mechanism for nutrient reduction is through biological control. Oyster repletion
efforts in the Bay are underway with a revised management plan with progressive new strategies
(CBP, 1994a). However, disease and parasites are affecting oyster recovery and repletion goals
are long-term. Other Bay species are also considered beneficial for their uptake and removal of
nitrogen, though it is unknown what quantity of nutrients is reduced by biological means.
SA V and Wetland Protection and Restoration
Action 6.2.1 of this Plan outlines the Chesapeake Bay Program directive for SAV
restoration (CBP, 1993; see Figure 15). The goals are supported and reinforced by this Plan. The
success of SAV restoration and protection is most dependent on nutrient reduction, as discussed
earlier. In addition, protection of existing SAV and future restoration efforts is dependent on
efforts to reduce sediment loads to the Bay. Wetland and riparian buffer protection and
restoration benefits SAV by preventing shoreline erosion, trapping sediments and absorbing
nutrients before they can enter the water. The Chesapeake Bay Program's Riparian Buffer
Directive (CBP, 1994c) seeks to protect and restore riparian buffers. A 1996 riparian forest
buffers initiative furthers the Bay Program's commitment to improving water quality and
enhancing habitat with the goal of increasing riparian buffers on 2,010 miles of stream and
shoreline in the watershed by the year 2010 (Chesapeake Executive Council, 1996). In 1988, the
Chesapeake Bay Program also established a "no net loss" policy for wetlands in the Chesapeake
Bay watershed with a long-term goal of net gain (CBP, 1988).
The Chesapeake Bay Program has identified threats to SAV from physical disturbance and
provides guidelines to protect existing and restored SAV habitat (CBP, 1995a). The highest
priority is to protect shallow water habitat that supports existing or potentially restored SAV
down to the one meter depth contour from physical disruption. The Chesapeake Bay Program
also recommends protection of shallow water habitat to the two meter contour. Shallow water
habitat is important to blue crabs and protection of shallow water habitats and SAV is of direct
benefit.
Protection and restoration of SAV and water quality is most important for blue crab in
areas where postlarval settlement and juvenile development occurs. Priority areas for SAV
restoration that specifically benefit the critical postlarval stage of blue crab have been identified
(Figure 14; Action 6.2.2, Table 4). Water quality monitoring results from segments within
28 Background
-------
Chesapeake Bay and its tidal tributaries that were within the likely range of postlarval blue crab
settlement, as defined by Orth et al. (1996), were identified by the Chesapeake Bay Program's
SAV Workgroup. Segments were classified into four categories by comparing SAV survey data
(from Orth et a/., 1995) and water quality data (CBP, unpublished data, 1984-present). Actions
are recommended for each category, based on two assessments: 1) the present amount of SAV
compared to the maximum extent mapped from 1978 to 1991; and 2) recent water quality
measurements in each segment in comparison with median water quality standards that support
SAV growth in different salinity zones within the Bay (Batiuk et al., 1992; Dennison et a/., 1993;
see Appendix B for decision matrix used to make recommendations in Action 6.2.2). In general,
SAV in a segment starts to increase when about 80% or more of the water quality habitat
requirements are met in that segment, especially when they have been met for several years in a
row (see Batiuk et al., 1992, for water quality requirements for SAV).
Toxics Reduction Strategy
In 1994, the Chesapeake Executive Council of the Chesapeake Bay Program adopted the
Chesapeake Bay Basinwide Toxics Reduction and Prevention Strategy (CBP; 1994b). The goal
of the toxics strategy is:
"a Chesapeake Bay free of toxics by reducing or eliminating the
input of chemical contaminants from all controllable sources to
levels that result in no toxic or bioaccumulative impact on the
living resources that inhabit the Bay or on human health. "
The strategy commitments go beyond point-source control, and begin to address the more
difficult tasks of controlling stormwater runoff and atmospheric deposition. Implementation of
efforts to identify the origin of nonpoint source toxics will be used to develop strategies to reduce
contaminants from those sources in the future.
RESEARCH NEEDS
Three categories for research needs can be identified for blue crabs: 1) biological data; 2)
economic profile data; and 3) data needs for management. The first two are directly related to the
third, data needs for management. Biological data needs include age and growth for more
precision and accuracy in stock assessments; a better understanding of life history, such as factors
that affect settlement and recruitment; and the effects of changes in habitat quality and quantity.
Economic profile data includes a characterization of the people of various segments of the
fisheries (commercial and recreational) and their practices. Both sets of information are valuable
for assessing the impact and effectiveness of various management strategies such as limits on
fishing effort, harvest restrictions, and limited entry. Other data needs that directly impact
management decisions include accurate fishery statistics and gear design studies. Priority research
needs are listed below:
Background 29
-------
1. Develop an accurate method and determine criteria that may be used to assess the age of
blue crabs and use these data to determine the age structure of the population and
longevity of the species.
2. Develop criteria that would define overfishing, its potential effects on the adult and
juvenile portions of the stock, and methods for recovering the stock should it become
overfished. Set stock targets and indicator triggers that will signal potential problems.
3. Determine annual estimates of spawning stock size and size of the recruiting year class and
examine their relationship and factors that affect their relationship.
4. Determine the level of spawning stock which would conserve reproductive potential in a
range of environmental conditions and develop prudent targets for the size of that stock.
5. Develop Chesapeake Bay-wide estimates of catch and effort by life history stage, year
class, sex, and gear type in the commercial and recreational fisheries.
6. Quantify the carrying capacity of habitats for different sizes and sexes of blue crabs to
identify critical areas of habitat which provide maximum blue crab productivity.
7. Obtain basic information pertaining to the reproductive biology of blue crabs and stock-
recruitment relationships.
8. Develop analytical models and supporting databases to evaluate the social and economic
conditions in the fishery and the effects of management and actions on those conditions.
9. Support fishery independent surveys to augment or refine collection and compilation of
fisheries data and improve and fully utilize the winter dredge survey, the only Baywide
sampling program.
10. Study the relationship between laws, regulations, and enforcement and the status of the
stock.
11. Encourage studies of atmospheric and aquatic environments of the continental shelf, their
effects on the blue crab larval and megalopal populations, and their relationship to stock
size of the blue crab in Chesapeake Bay.
12. Evaluate sources of natural mortality (including predation mortality rates) at various life
history stages of the blue crab.
The blue crab is a complex animal with a complex life cycle. Although understanding of
this species has grown, there is still much that is unknown. Research needs will continue to be
identified through the Bay Program, and in particular through the Chesapeake Bay Commission's
30 Background
-------
Bi-State Blue Crab Advisory Committee. This committee has a Technical Workgroup (comprised
of leading crab scientists and economists from around the Bay region) which advises them on
research needs and management issues. There is a strong working relationship between the Bi-
State Blue Crab Advisory Committee and the partners in the Chesapeake Bay program that will
ensure that expanding knowledge of the blue crab and its fishery is incorporated into the
Chesapeake Bay Program's Fishery Management Plan and the fishery and habitat management
programs of the jurisdictions.
Background 31
-------
SUBMERGED AQUATIC VEGETATION
(SAV)
LARVAE
POSTLARVAE
JUVENILES
MATURE MALES
MATURE FEMALES
Figure 1. Life history" of blue crab in Chesapeake Bay.
1. Larvae are hatched in lower Bay and exit into adjacent coastal waters.
2. Larvae develop and re-enter the estuary as postlarvae.
3. Postlarvae settle in lower Bay, particularly in beds of SAV, and develop into juvenile crabs.
4. Juvenile crabs disperse into tributaries and up the Bay.
5. Mature males and females mate in mid-salinity waters.
6. Females migrate to high salinity waters in the lower Bay, develop eggs, and spawn.
7. Males move into lower salinity waters up tributaries and in the upper Bay.
32
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Figure 6. Soft and peeler landings and
values in Chesapeake Bay.
Source:
VA -1952-72, NMFS; 1973-95, VMRC; new reporting system implemented 1993.
MD - 1952-79, NMFS; 1980-95, MDNR
38
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42
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Figure 11.
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VMRC Plans & Statistics
43
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CRAB TROTLINE LICENSES
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NUMBER OF LICENSES.
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NUMBER OF LICENSES
SO SS 70 71 SO S( SO SS
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Figure 12. Virginia trotline,
scrape and crab trap licenses.
600
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CRAB SCRAPE LICENSES
1960 - 1996
NUMBER OF LICENSES
«0 66 70 76 80 86 90 96
YEAR '
SOURCE, VMRC. PLANS t STATISTICS DEPT.
44
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Figure 13a. Landings from Virginia's commercial dredge fishery and average landings
for the periods indicated. NMFS and VMRC data.
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Figure 13b. Adult female crab abundance (catch per unit effort) from
VIMS/W&M trawl survey by year for 1956-1992. Note the relatively low level of
abundance during the past two decades. Dashed lines indicate means for each
period shown. Survey areas were the York, James and Rappahannock Rivers.
45
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VIMS/W&M Index
Figure i3C Indices of stock abundance (catch per unit effort) for
1981-1993. Shown are the commercial dredge harvest and the
adult female index from the VIMS trawl survey. The lower plot is
the resulting regression of dredge harvest on adult female index,
with years indicated.
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SECTION 2
BLUE CRAB MANAGEMENT IN CHESAPEAKE BAY
Management of the Chesapeake Bay blue crab stock across geographic regions and state
boundaries is a dynamic and complicated process. Since the adoption of the 1989 Chesapeake
Bay Blue Crab FMP (CBP, 1989), management measures implemented in Maryland and Virginia
limit entry into the fishery and attempt to cap fishing effort. The following sections summarize
Baywide management strategies and actions since 1989 and provide a framework for management
strategies in the years to come. For a complete list of regulations and legislation pertaining to blue
crabs, see Appendix C.
Coordinated Baywide Management Efforts
In January, 1996, the Chesapeake Bay Commission formed the Bi-State Blue Crab
Advisory Committee, an ongoing committee of representatives from Maryland and Virginia. The
committee will meet at least twice each year to address key elements of the Blue Crab Fishery
Management Plan and other mutual interests. The Bi-State Blue Crab Advisory Committee offers
a discussion and decision forum that supports state efforts to develop consistent and coordinated
Baywide crab management policy. The committee consists of eight members each, from the
Virginia and Maryland blue crab advisory committees (Maryland's Blue Crab Steering Committee
and Virginia's HJR 609 Committee); six additional members from the Maryland and Virginia
Delegations to the Chesapeake Bay Commission; the chair of the Bay Program's Living
Resources Subcommittee; and a representative from the Potomac River Fisheries Commission
(PRFC). The above membership represents the principal appointed officials of marine resources
from each state, key legislators, watermen, fisheries managers, recreational crabbers, and
individuals from the crab industry. Importantly, this membership approach continues the core
representation of each state's crab committees, which have already taken the first steps toward bi-
state action through joint meetings and ongoing communication. A select group of scientists and
economists will serve as a Technical Workgroup to examine ecological and economic issues,
analyze current data, and distill relevant fishery information for the committee's review.
Management Measures Since 1989
Virginia
Authority
The Virginia Marine Resources Commission (VMRC) is the state regulatory agency
charged with managing marine resources in tidal waters. Regulations are adopted by a panel of
commissioners appointed by the Governor. Virginia's legislative body, the General Assembly,
52 Blue Crab Management in Chesapeake Bay
-------
defines the regulatory authority of VMRC and also votes on legislation in addition to regulations
passed by VMRC.
Regulatory and Legislative Changes Since 1989
In June 1989, VMRC restricted crab dredging from sunrise to sunset through regulation.
In June 1990, a regulation was promulgated governing the use, placement and maintenance of
crab traps/pounds. At the General Assembly level, a bill was passed in 1990 that prohibited the
placement of crab, eel or fish pots in a government marked channel. In 1991, House Joint
Resolution #384 was passed which directed the Chesapeake Bay Commission to establish a
committee to study issues related to the conservation of the living resources of the Chesapeake
Bay. Consequently, the Living Resources Roundtable was formed and began meeting in May
1991. The 1992 session of the General Assembly passed a law, as recommended by the Living
Resources Roundtable, which required that all commercial fishermen obtain a registration license.
A two-year delay process was established for new entrants. The VMRC was given authority to
limit or delay the number of participants entering any specific fishery, to require catch reports, and
to delay the start of the crab dredge season until after December 1. In addition, the crab pot
removal period was shortened by two weeks, to January 1-31.
In August 1992, Virginia adopted a regulation that established the procedures for the
registration of commercial fishermen and the manner and form of mandatory harvest reports. This
has provided more complete data and information to manage the crab fishery.
In 1993, the Virginia General Assembly enacted a law authorizing VMRC to establish
recreational gear licenses. In other action, the commercial license fee structure for crab gear was
revamped. New commercial licenses were established, including a peeler pot license and a license
for shedding crabs. A regulation was promulgated in May, 1993, by the VMRC which established
recreational licenses for up to five crab pots, one crab trap/pound and one crab trotline. In June
1993, the Commission passed a regulation designed to conserve small crabs, which required one
unobstructed cull ring (25/16 inches diameter) in each hard crab pot, effective January 1, 1994.
At their November meeting, the VMRC held public hearings and considered several proposals
pertaining to controlling fishing effort and minimizing wasteful harvesting practices. After
receiving public comments, the Commission reduced the daily catch limit in the crab dredge
fishery from 25 to 20 barrels per vessel and established a limited entry system for the crab dredge
fishery. The number of crab dredge licenses issued as of March 31, 1994, would be set as the
maximum number for future seasons and the maintenance level was set at 225.
The 1994 session of the General Assembly removed the specifications for crab dredge
dimensions in the Code of Virginia and authorized the VMRC to promulgate a regulation limiting
the size of crab dredges. For the 1994/95 dredge season, the maximum dredge width of eight feet
was reestablished. In October, 1994, Virginia approved a regulatory package of seven
conservation measures for the blue crab commercial fishery. A 14,500-acre winter crab sanctuary
was established upriver from the Hampton Roads Bridge Tunnel and dredging was prohibited in
that area. A second summer spawning sanctuary (48,000 acres) was established Bayside of
Kiptopeke on the Eastern Shore and crabbing was prohibited from June through September 15.
Language was removed from the regulation allowing obstruction of cull rings during economic
hardship. A second, smaller cull ring with an inside diameter of 2 3/16 inches was mandated in all
Blue Crab Management in Chesapeake Bay 53
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hard crab pots. To address the issue of small mature females escaping through cull rings in certain
areas, the larger (2-5/16 inches) cull ring was allowed to be closed within the dredge boundaries,
in Pocomoke and Tangier sounds as well as on the seaside of the Eastern Shore. Four cull rings
were required (1-1/2 inches inside diameter) in each peeler pound. Gear limits were set on peeler
pots with 400 pots per vessel from April through June, and a 400 pot per person limit from July
through November with no more than two licensed peeler potters allowed per vessel. A season
was also established, whereby peeler and hard crab pots must be removed from the water by
December 1 and not set out again until April 1.
In 1995, the General Assembly authorized the City of Norfolk to declare Pretty Lake a
crab sanctuary by adoption of an ordinance. In other action, the placement of food in peeler pots
was prohibited; previously, it was lawful to place food for jimmy crabs in peeler pots from
September 16 through May 14. House Joint Resolution 609 (HJR 609) directed the Virginia
delegation to the Chesapeake Bay Commission, VMRC and four industry representatives to study
blue crabs. It also recommended a Blue Crab Fishery Management Plan (FMP) be prepared by
VMRC, in consultation with research institutions and representatives of industry. The FMP was
to be designed to reverse any fishing practices, environmental stress and habitat deterioration
negatively impacting the short-term and long-term viability and sustainability of the crab stock in
Virginia waters.
The HJR 609 Committee met several times during 1995. Scientists presented technical
reports on the status of the crab resource, including spawning stock information, survey results
and research needs. Managers reviewed a draft of the 7997 Chesapeake Bay Blue Crab FMP, and
presented current management policies and field research. The Committee voted not to change
the current minimum sizes of crabs in 1995, primarily because consistency among Atlantic and
Gulf coast states was needed. Members endorsed a proposal to establish a minimum 3!/2 inches
size for soft crabs instead of cull rings in peeler pots. The Committee also voted to recommend
legislation which will allow VMRC to define, by regulation, peeler crabs in order to reduce
mortality. In addition, the HJR 609 Committee recommended that the 1997 Chesapeake Bay Blue
Crab Management Plan be adopted as Virginia's Plan, with a few revisions including: enhanced
provisions regarding SAV; updated regulatory actions by the VMRC; and continued bi-state
coordination and cooperation.
The 1996 session of the General Assembly authorized VMRC to modify the statutory
definition of peeler crab, by regulation and authorized greater flexibility in setting the crab dredge
season, based on conservation factors. Language clarifying the crab cull law was also adopted. In
February 1996, Virginia adopted several regulations designed to protect and conserve the blue
crab resource. A minimum size limit of 3 Va inches was established for softshell crabs and a
prohibition on the possession of dark sponge crabs was passed. Limits on the sale of commercial
hard crab and peeler pot licenses for 1996 were established. Crabbers who held pot licenses in
1995 were allowed to purchase licenses for the same amount of pots in 1996. Crabbers with a
history of potting and crew who obtained documentation were granted restricted licenses and
hardship exception cases were considered. In addition, maximum daily hard crab pot limits were
set. Crabbers were restricted to 300 crab pots in the tributaries or 500 pots in other tidal waters;
however, no person could set more than a maximum of 500 pots statewide.
54 Blue Crab Management in Chesapeake Bay
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Maryland
Authority
Maryland's Department of Natural Resources (MDNR) is the state regulatory agency
charged with managing fisheries in state waters. Authority to regulate is granted to MDNR by the
Maryland State Legislature. The Maryland State Legislature must approve any changes to the
fishing license structure and votes on legislation in addition to regulations passed by MDNR.
Regulatory and Legislative Changes Since 1989
Prior to 1994, there was no limit on the number of crab pots a commercial fishermen
could fish in Maryland. A new license structure, which took effect in 1995, retains the Limited
Crab Harvester License (up to 50 pots) and consolidates licenses for more than 50 pots and all
other gears into one Crab Harvester License. Crab Harvesters are limited to 300 crab pots per
vessel, and licensees may buy single and double allocations for one to two crew members which
permits 300 additional pots per allocation, not to exceed 900 pots per boat. The Tidal Fish
License, which consolidates finfish, shellfish and crabs in one license, is also limited to 300 pots
with allocations up to 900 pots per boat. The deadline for crew authorization application was
August 31, 1994.
In 1994, Maryland passed legislation that limits new entries into the commercial fishery.
The Limited Entry Bill gives MDNR authority to establish a prescribed number of people to
participate in any given fishery. No new licenses have been issued since April 1, 1996. The license
moratorium will remain in effect until the number of licenses drops below a prescribed number,
which will be determined by 1999. As licenses are lost voluntarily, by revocation, expiration or
death, the fishery will be capped at a maximum number of participants, and fishing effort will be
limited.
In 1994, times when commercial and recreational crabbers can set and fish their gear in
Maryland were defined in regulation (see Appendix C). To limit effort in the number of man-hours
spent fishing, start and end times were staggered to minimize conflicts between user groups.
The noncommercial crab license was eliminated through legislation prior to the 1994
harvest season. Maryland currently has no licensing system for recreational crabbers, which
includes crabbers who were previously licensed as noncommercial crabbers since 1994.
Unlicensed recreational crabbers were limited to five crab traps and/or rings per person; the
licensed noncommercial crabber was allowed up to 50 traps and/or rings. All recreational crabbers
since 1994 have been limited to 10 traps and/or rings per person, not to exceed 25 traps and/or
rings per boat. Trotline, which was limited to 500 feet for recreational crabbers and unlimited for
noncommercial crabbers, is now limited for all recreational crabbers to 1000 feet per person, not
to exceed 2000 feet per boat. Recreational harvest since 1994 has been limited to no more than
one bushel per person and no more than two bushels per boat. A recreational crabbing license was
proposed to the Maryland Legislature in 1994, 1995 and 1996, but was not adopted. The
Maryland General Assembly is considering a bill during the 1997 Session that would require
recreational crabbers to purchase a license, excluding recreational crabbers using handlines or
dipnets, and private property owners using crab pots from their property. Revenues would fund
an extensive survey of the recreational fishery.
Blue Crab Management in Chesapeake Bay 55
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Cull rings enabling undersized crabs to escape have been used on a voluntary basis for
several years. Current Maryland regulation requires one cull ring 2 5/16 inches in diameter or one
section of 2 inches by 2 inches square mesh with four openings in all crab pots with mesh size
greater than 1 !/2 inches or less than 2 inches. The cull ring may be obstructed at any time of year
for the purpose of catching peelers.
The maximum number of crab pots that can be set from private property in Maryland is
two. Prior to 1994, some counties were allowed four. The proposal that pots be set or
constructed so trapped air-breathing animals could survive until released was rejected.
In 1996, Maryland passed a regulatory package for blue crabs. All commercial harvest was
prohibited one day per week and recreational harvest by trotline, traps, and rings was prohibited
one day per week. A second cull ring 2 3/16 inches in diameter was required in all crab pots with
mesh at least 1 !4 inches and less than 2 inches. Hard crab pots were redefined as pots with mesh
1 '/2 inches and greater. Peeler pots must have at least 1 inch mesh.
Potomac River Fisheries Commission
Authority
Blue crab fishery activity on the tidewater portion of the Potomac River is managed by the
Potomac River Fisheries Commission (PRFC), an eight-member body empowered under the
Maryland-Virginia Compact of 1958. The Commission meets quarterly to establish and maintain a
program of conservation and improvement of the fishery resources of the river. The Commission
will develop appropriate Actions and Implementation plans, along with Maryland and Virginia, to
address the Problems and Strategies identified in this Management Plan.
Regulatory Changes Since 1989
The Potomac River Fisheries Commission (PRFC) implemented limited entry into the
commercial crab pot fishery, beginning in 1995. Entrants had until January 31, 1995, to renew
existing licenses or to become eligible to receive a commercial license. Issuance of commercial
crab pot licenses will be capped at 500.
Improvements in Catch Statistics
Commercial reporting systems in Virginia (VMRC) and Maryland (MDNR) surveyed a
portion of harvesters (MD, 1981 to 1994) or dealers (VA, 1973 to 1993) each month. Reporting
in Virginia was voluntary and Maryland conducted random samples. Since 1993, both states have
converted to mandatory reporting by all commercial harvesters and collect information on
amounts of gear and effort, as well as biological characteristics of the catch. Because the various
life history stages of blue crab are found in different areas of the Bay and the population is
assumed to represent a single stock across state lines, uniform Baywide catch records for both
commercial and recreational harvests are necessary to adequately monitor the resource.
56 Blue Crab Management in Chesapeake Bay
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Evaluation of Blue Crab Management
Implementing a combination of effort control management strategies, i.e. gear, time and
license reductions or stabilization, may be effective at containing harvest (National Academy
Press, 1994). Although the current regulations on the harvest of blue crabs are significant for both
states, it is not yet clear at what level effort may be capped. Maryland's gear limit for crab potters
still allows for growth in the fishery. In years prior to gear limits, a large portion of harvesters
reported using 200 pots or less. A limit of 300 pots per person may permit effort in the fishery to
increase before it stabilizes. In addition, crew allocations allow for up to 900 pots per boat and
crew members may be unlicensed. License stabilization in the form of the 1994 limited entry law is
a giant step towards stabilizing effort in the entire Maryland crab fishery. Maryland has not yet
defined what number of licenses the fishery will be capped at. Levels of harvest and harvest rates
in following seasons will likely determine whether the fishery should be capped at current license
levels or if reduction is necessary.
Virginia recently adopted a regulation which limits the amount of effort in the crab pot
fisheries by two methods for the 1996 crab season. This regulation was designed to protect and
conserve the blue crab resource by limiting the number of commercial hard crab pot and peeler
pot licenses issued and to further control fishing effort by establishing limits on the number of
commercial hard crab pots that can be set or fished. Another regulation was already in effect that
restricts the number of peeler pots that can be set or fished. This new regulation, in combination
with all of the other conservation measures that Virginia has implemented within the last few
years, is designed to stabilize fishing effort, increase productivity and conserve the blue crab
resource.
Conclusion
Managers from both jurisdictions are careful not to assume recent regulations will be
completely effective in limiting effort and harvest in the fishery. These new restrictions and their
effectiveness at stabilizing fishing effort must be evaluated. If these actions prove successful in
limiting fishing effort on the blue crab stock in Chesapeake Bay, this management plan will have
succeeded in the objective of being a "problem preventing" tool rather than solely a "problem
solving" plan.
This Plan is designed to be flexible and responsive to new knowledge, changes in stock
abundance or fishing mortality rates, and new or revised estimates of stock status. Future
management decisions will also depend on the effectiveness of current regulations. Virginia and
Maryland still have substantial differences in their management regulations. Although the states
are striving for uniformity, differences in regulations are often the result of life history and
behavioral characteristics of the blue crab and differences in the fisheries. Therefore, compatibility
of regulations may be more appropriate in some instances.
Over the course of the next several years, intensive research and monitoring will be
necessary to evaluate whether the Bay states have insured the long-term survival of the blue crab
resource or whether new solutions must be sought to preserve the resource. Maryland and
Blue Crab Management in Chesapeake Bay 57
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Virginia should continue their cooperative approach in the management and study of this species.
Forums such as the Bi-State Blue Crab Advisory Committee will be valuable in assuring open
communication and discussions regarding the most up-to-date science, effectiveness of current
regulations, and needed changes to management actions.
58 Blue Crab Management in Chesapeake Bay
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Blue Crab Management Strategies
1. Stock Status
Problem LI: Stock Status
Estimates of stock abundance (Rugolo et a/., unpublished) indicate that the blue crab
population was high in the late 1980s through 1991 and has returned to average levels of
abundance since 1991. Juvenile recruitment indices have been increasing and estimates of fishing
mortality have varied without trend between 0.8 and 1.0 (1968-1995). The blue crab fishery is
characterized as fully exploited. This description is based on a fishing mortality rate that allows for
at least 10% of the spawning stock to escape the fishery to reproduce (F10%; i.e. the estimated
weight of the adult female stock if no crabs were removed by the fishery, divided by the estimated
total weight of the current adult female stock as influenced by fishing pressure, equals 0.10 or
10%). Results of the Chesapeake Bay blue crab stock assessment indicate that fishing mortality
rates have remained at or slightly below estimates of F10% . Although the results of the stock
assessment are positive for the blue crab stock, they do indicate that the fishery is overcapitalized
(refer to Problem 2.1: Fishing Effort). As long as the fishery does not become more efficient at
harvesting blue crabs, the stock should be able to sustain the current level of fishing pressure.
Strategy 1.1
To provide long-term protection for the blue crab stock and maintain a stable stock,
quantitative targets (such as abundance, biomass, or other indices) will be developed as references
for evaluating stock status and implementing fisheries or habitat management measures. Targets
will be the safe management levels. Limits will be the maximum limits for sustainability.
Actions
L1.1 The Baywide blue crab stock assessment will be updated in 2 years, and every 5
years thereafter, to monitor trends in the blue crab population. New information
from other assessments will be evaluated, as well.
Implementation: 1998
1.1.2 The Chesapeake Bay Blue Crab Target Setting Task Force will: 1) examine habitat
and environmental variables as they relate to stock size and recruitment; 2)
examine blue crab harvest and abundance by life history stage, time, and area; and
3) develop a regional, stage-based model to predict life stages and regions of
greatest sensitivity of blue crab to changes in exploitation patterns and rates.
Implementation: 1998
1.1.3 The Chesapeake Bay Commission Bi-State Blue Crab Advisory Committee, a joint
panel of legislators, representatives of the industry and commercial and
recreational fisheries, and other interests from Maryland and Virginia, will convene
twice a year to review the status of the blue crab resource baywide and the
effectiveness of current regulations and coordinate efforts. Data and assessments
Blue Crab Management in Chesapeake Bay 59
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will be provided to the panel by a technical committee of scientists and resource
managers. The panel, based on information provided by the technical committee,
will recommend actions as necessary to stabilize harvest and effort at levels that
protect the reproductive potential of the blue crab stock.
Implementation: 1996
/. 1.4 The Technical Workgroup (TWO) of the Chesapeake Bay Commission's Bi-State
Blue Crab Advisory Committee (BBCAC) will assess the economic impacts and
benefits of various biologically-determined limits and target levels. In addition, the
TWO will assess the economic ramifications of policies designed to stabilize
harvest and effort levels which protect the reproductive potential of the blue crab
stock.
Implementation: Ongoing
/. 7.5 The states will develop estimates of prudent and sustainable spawning stock which
gives reasonable promise that the spawning stock will not be so depleted as to
reduce future abundance.
Implementation: Ongoing
2. Fishing Effort
Problem 2.1: Fishing Effort
Prior to 1994, Maryland and Virginia fisheries were open access, with no limits the
number of participants and few limits on amounts of gear. As a result, baywide fishing effort for
blue crab has increased five-fold since 1945. Over this same time period, fishing mortality and
total harvest have remained stable. However, high numbers of participants in the fishery, increased
competition between participants, and subsequent overcapitalization of the commercial fishery
have resulted in a decreased CPUE. Harvesters must deploy greater amounts of gear to harvest
equal amounts of crabs. Only limited information regarding fishing effort and harvest in the
recreational fishery is available.
Strategy 2.1
Limited entry in the commercial fishery is being implemented in Maryland, Virginia and
the Potomac River. In addition, limits on commercial and recreational fishing effort were recently
enacted and a design for a baywide survey of recreational catch and effort is being developed. The
implementation of these management measures will be monitored and evaluated to determine
effectiveness of capping effort, preservation of the social value, and economic sustainability of the
fisheries.
Actions
2.1.1 Maryland will determine a maximum number of commercial crabbing licenses and
licenses with crew allocations, as required under the state's Limited Entry Law
60 Blue Crab Management in Chesapeake Bay
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(Annotated Code of MD, Nat. Res. Article 4-701). Maryland shall consider the
number of people historically participating in the fishery, annual harvest, mortality,
total biomass, size, number, incidental catch, target species, and any other factors
that are necessary and appropriate. ,
Implementation: 1998
2.7.2 Virginia will continue to evaluate its crab pot and peeler pot limited entry program
which was established January 1, 1996. Further adjustments to the program will
depend on the future status of the stock and stabilization of the fishery. Minor
adjustments to the program will be necessary to insure its long-term application.
Implementation: 1997
2.1.3 The Potomac River Fisheries Commission (PRFC) will continue to evaluate its
crab pot limited entry program.
Implementation: Ongoing
2.1.4 Maryland, Virginia, and the PRFC will continue to manage blue crab fisheries
through the use of time limits, seasons, gear restrictions, catch limits, and size
limits, as necessary, to prevent further increases in fishing effort.
Implementation: Ongoing
2.7.5 Maryland will design a survey that estimates catch and effort by the recreational
fisheries in Maryland and which could be applied baywide. Virginia will continue
to monitor licensed recreational crab harvest data.
Implementation: Maryland, 1999; Virginia, ongoing.
2.7.6 The Technical Workgroup of the Bi-State Blue Crab Advisory Committee will
design sample survey procedures that can be used to build a comprehensive effort
and economic data base for the fishery. Cost estimates for implementation of the
surveys will be provided.
Implementation: 1999
Problem 2.2: Gear Efficiency
With the exception of the scrape fishery and winter dredge fishery, which are both limited
in size and area, the blue crab fishery uses passive gears that allow for escapement of a portion of
the blue crab population. Changes in the efficiency of the fishery, such as improved gear designs
or new gears, have the potential to harvest a greater portion of the blue crab population and
overexploit the resource.
Blue Crab Management in Chesapeake Bay 61
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Strategy 2.2
The jurisdictions will continue to monitor trends in the commercial and recreational
fisheries and manage those fisheries in a manner that allows adequate escapement of blue crabs
from harvest and prevents overfishing.
Action
2.2.1 Maryland and Virginia have defined gear for the purpose of catching crabs through
regulation and legislation (Appendix C). Any major changes to gear, as currently
defined, will be evaluated prior to approval to determine the potential impacts on
the efficiency of the blue crab fishery and fishing mortality rates.
Implementation: Ongoing
2.2.2 Maryland, Virginia and the PRFC have modified reporting methods to acquire
more accurate and detailed data. The mandatory reporting systems collect data on
areas fished, gear types and amounts, hours fished, amounts harvested, and
biological data. New reporting methods will continue to be used to monitor effort
in the commercial fisheries, including effort by life history stage, sex, and gear
type. The jurisdictions will continue to coordinate efforts to develop compatible
reporting systems. The effectiveness of current regulations also will be monitored
through reporting methods.
Implementation: Ongoing
3. Stock Assessment Needs
Problem 3.1: Commercial Reporting
Virginia and Maryland implemented mandatory reporting by all commercial harvesters in
1993 and 1994, respectively. The states collect data on fishing effort, harvest by area, and harvest
by market category (male, female, soft/peeler). The PRFC also requires reporting of similar data
by all commercial harvesters on Potomac River. Further refining of data collection and analysis
may be necessary to obtain consistent data sets that are comparable across jurisdictions. Prior to
1993, Virginia's reporting system did not collect data on effort or market category and it will take
several years before trends and comparisons become apparent.
Strategy 3.1
New reporting methods will be used with continued fishery-independent surveys to
monitor blue crab stocks.
Actions
3.1.1 Maryland, Virginia, and PRFC will continue to collect comparable data and refine
data collection to achieve greater consistency.
Implementation: Ongoing
62 Blue Crab Management in Chesapeake Bay
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3.1.2 Maryland and Virginia will monitor commercial landings to evaluate the
relationship between fishery-dependent and fishery-independent estimates of
abundance and coordinate management efforts.
Implementation: Ongoing
3.1.3 Maryland and Virginia will explore methods to collect more accurate data on soft
and peeler crab harvest.
Implementation: 1998
Problem 3.2: Recreational Harvest
Little is known about the blue crab recreational catch, fishing effort, and the economic
impact of recreational crabbing in Chesapeake Bay. Virginia instituted mandatory reporting for all
licensed recreational crabbers, including the amount harvested per day, amount and types of gear
used, and area. A license is required in Virginia for recreational use of up to 5 crab pots, 300 feet
of trotline and/or one crab pound/trap. Maryland has been unsuccessful in attempts to require
recreational licenses since 1994 and recreational harvest is unreported. The Potomac River
Fisheries Commission has twice considered a recreational crab pot license as a tool to collect
recreational data, but no license has yet been enacted for the Potomac.
Strategy 3.2
There will be a baywide effort to collect recreational catch and effort data. The economic,
social, and biological impact of the recreational harvest will be evaluated.
Action
3.2.1 Maryland will consider a recreational crabbing license to complement efforts
outlined in Action 2.1.4 to obtain recreational catch and effort data.
Implementation: 1997
Problem 3.3: Research Needs
The population dynamics of the blue crab stock is not fully understood. Additional
information is needed concerning natural and fishing mortality rates, as well as the stock-
recruitment relationship. The effects of environmental variables and fishing mortality on year-class
strength and availability, female spawning potential, age, and growth are also areas that require
improved understanding.
Strategy 3.3
The baywide effort to collect population data on blue crabs will continue and current
methods will be improved.
Blue Crab Management in Chesapeake Bay 63
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Actions
3.3.1 Maryland and Virginia will continue cooperation with the Baywide Winter Dredge
Survey. Data analysis will be refined.
Implementation: Ongoing
3.3.2 Maryland and Virginia will continue to encourage research that examines the
relationships between spawning stock and recruitment and the effects of
environmental parameters on fluctuations in crab abundance.
Implementation: Ongoing
3.3.3 Signals of year class abundance early in the life history will be sought and
evaluated as guides or triggers for management actions.
Implementation: Ongoing
3.3.4 Studies of the stock of blue crabs on the ocean side of the Eastern Shore, its
abundance and economic value, and its potential contribution to the larval and
megalopal stock on the continental shelf that may eventually become part of the
Bay stock are encouraged.
Implementation: Ongoing
3.3.5 Age and growth studies will be emphasized.
Implementation: Ongoing
4. Wasteful Harvesting Practices
Problem 4.1: Economic Yield
Harvesting small crabs or buckrams does not maximize economic value of the resource.
For example, the economic yield of crabs is not always optimum if buckrams (recently shed crabs
whose shell is in the process of hardening), which yield small amounts of meat, are marketed.
Strategy 4.1
Optimum use of the blue crab resource will be promoted by eliminating and/or minimizing
wasteful harvest practices. Harvesters and consumers should be educated concerning poor-quality
or poor-value crabs.
Actions
4.1.1 Size limits which achieve the greatest economic yield for the fishery will be
evaluated.
Implementation: 1997
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4,1.2 Maryland and Virginia will continue to promote the release of buckrams through
brochures and/or newsletters that identify buckrams and demonstrate the potential
weight gain through time.
Implementation: Ongoing
4. L3 Maryland and Virginia will educate the consumer about wasteful harvesting
practices and the effects of waste on the resource, so consumers may be better
informed when purchasing crabs.
Implementation: 1997
Problem 4.2: Cull Apparatus
Small crabs retained in hard crab pots suffer high mortality rates due to predation by larger
crabs. Cull rings may also allow the escape of small, legal-size peelers and mature females during
certain seasons. Cull rings that allow sublegal crabs to escape are required in all jurisdictions;
however, legislation in Maryland allows cull rings in hard crab pots to be obstructed when fishing
for peelers through 1999.
Strategy 4.2
The biological benefits and economic impact of cull rings in crab pots will be investigated.
Maryland will define specific seasons when cull rings may be obstructed for harvesting peelers,
considering both impact on the resource and economic benefit.
Actions
4.2.1 Maryland will define seasons for peeler fishing with hard crab pots (pots with mesh
size 1.5 inches or greater) for which cull rings may be obstructed to minimize the
impact on the resource and maximize economic benefits. Outside of the defined
season, unobstructed cull rings will be enforced.
Implementation: 1997
4.2.2 Legislation in Maryland allowing cull rings in hard crab pots to be obstructed when
fishing for peelers is effective through 1999. Maryland will evaluate the effects of
requiring unobstructed cut! rings and identify management options with minimum
economic impact and maximum benefit to the resource. Seasonal obstructions and
cull ring placement and size should be considered.
Implementation: 1997
4.2.3 The Potomac River Fisheries Commission will require two cull rings (one 2 5/]6
inches minimum and one 2 3/16 inches minimum) in hard crab pots and two cull
rings 1 '/2 inches minimum in peeler pots.
Implementation: 1997
Blue Crab Management in Chesapeake Bay 65
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Problem 4.3: Female Harvest Rates
The harvesting of sponge crabs and females at other life history stages may result in a loss
of reproductive capability.
Strategy 4.3
Landings and fishery-independent data will be reviewed to determine if low reproductive
potential and poor spawning success are resulting from female harvest.
Actions
4.3.1 Virginia and Maryland will continue to collect data on female size at maturity,
migration, distribution, and harvest by sex. This data will be used to examine the
effects of female harvest on crab population dynamics. Result will be used to guide
management measures that protect the reproductive potential of blue crabs.
Implementation: Ongoing
4.3.2 Maryland will investigate the interstate trade of blue crabs to quantify the number
of sponge crabs entering the Maryland market. Sponge crabs may not be legally
harvested in Maryland. The state will investigate the economic impact of
prohibiting possession or sale within the state.
Implementation: 1997
4.3.3 Maryland and Virginia will evaluate studies that examine the effectiveness of
sanctuaries as a conservation tool. Sanctuaries include areas where harvest is
prohibited seasonally and year-round, and protected nursery habitats. States will
consider establishing sanctuaries in areas identified as optimum sites in Chesapeake
Bay.
Implementation: 1997
Problem 4.4: Abandoned Pots
Lost and abandoned crab pots are attractive refuge sites that trap and, eventually, kill
significant numbers of crabs and finfish. Pots are lost when boat propellers cut buoy lines, during
storms, and by sabotage. Pots also may be crushed by clam dredging. Abandoned pots are self-
baiting. Weak and dead crabs attract other crabs into abandoned pots. Abandoned pots trap and
drown air breathing animals, such as terrapins, that inhabit tributaries. Biodegradable materials
and escape panels have been the subject of preliminary investigation in Maryland. In addition to
being a hazard to aquatic life, abandoned pots can be navigational hazards for boats. Enforcement
of regulations that prohibit pot abandonment is difficult and fines are not significant enough to
discourage the practice.
Strategy 4.4
The deliberate abandonment of crab pots will be discouraged and escape mechanisms on
pots will continue to be researched.
66 Blue Crab Management in Chesapeake Bay
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Actions
4,4.1 Virginia and Maryland will continue to address regulation of abandoned crab pots,
including significant fines that may discourage deliberate abandonment.
Implementation: 1996
4.4.2 Virginia and Maryland will continue to investigate materials for biodegradable
escape panels and latches in crab pots. Escape mechanisms for air breathing
animals and devices to prevent them from entering crab gear will also be
investigated.
Implementation: Ongoing
4.4.3 Maryland and Virginia will educate commercial crabbers about the problems of
abandoned crab pots and Maryland will educate property owners about the effects
of pots left unfished.
Implementation: 1996
4.4.4 The Potomac River Fisheries Commission will provide a mechanism to identify and
remove abandoned crab pots.
Implementation: 1996
Problem 4.5: Shedding Mortality
The mortality rate of green crabs (a peeler crab without red or pink coloration in the swim
fin) held in shedding floats is high compared with peelers that are close to molting. Mortality rates
in shedding floats and poorly operated shedding systems also may be high.
Strategy 4.5
Information will be provided to shedders to minimize mortality in shedding operations.
Actions
4.5.1 Maryland and Virginia will continue to provide technical information to shedding
operations that promote reduction of peeler mortalities associated with holding
practices and problems related to green crab mortality.
Implementation: Ongoing
4.5.2 Virginia established a commercial shedding license, effective January 1, 1994, and
will monitor data reports.
Implementation: Ongoing
4.5.3 Maryland will investigate a joint venture with commercial watermen's associations
to establish a shedding facility for the purpose of research and education.
Implementation: To be determined.
Blue Crab Management in Chesapeake Bay 67
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5. Regulatory Issues
Problem 5.1: Commercial/Recreational Conflict
The blue crab fishery provides economic, social, and recreational benefits to the
community. Conflict between commercial crabbers and recreational boaters has become a serious
problem in some of the more densely populated areas of Virginia and Maryland. From the
recreational boater's point of view, crab pot floats are interfering with recreational boating. From
the commercial waterman's perspective, recreational boaters are interfering with crab potting,
because they inadvertently run over and cut off crab pot floats. There is competition for trotline
space in Maryland tributaries.
Strategy 5.1
Conflicts among user groups and the general boating public can be minimized by time
limits, daily harvest restrictions and gear restrictions to allocate use of the resource.
Action
5.1.1 Maryland and Virginia will continue to monitor conflicts between crabbers and
recreational boaters, enforce existing regulations on open and closed crabbing
areas and buoy-free channels, and consider additional buoy-free channels.
Implementation: Ongoing
5.7.2 The Potomac River Fisheries Commission will continue to prohibit placement of
crab pots in federally marked navigation channels.
Implementation: Ongoing
Problem 5.2: Enforcement
The interstate shipment of crabs between states with inconsistent size limits and other
restrictions may circumvent efforts to protect the Chesapeake Bay stock from illegal fishing
activities. Enforcement of regulations is necessary to deter illegal fishing activities; however,
regulations such as gear limits are often difficult to enforce.
Strategy 5.2
Maryland and Virginia will continue to work towards complimentary management of the
baywide blue crab resource and improve enforceability of current regulations.
Actions
5.2.1 Maryland and Virginia will work to achieve consistent minimum sizes and
comparable conservation measures, where possible, for all crabs harvested in
Chesapeake Bay.
Implementation: Ongoing
68 Blue Crab Management in Chesapeake Bay
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5.2.2 Virginia will investigate the feasibility of a crab pot tagging system to improve the
enforceability of gear limits.
Implementation: 1997
5.2.3 The Potomac River Fisheries Commission will impose a 3 '/2 inches minimum size
limit on soft crabs.
Implementation: 1996
6. Habitat Issues
Problem 6.1: Anoxia
Excess nutrients enter the Bay from agricultural and urban runoff, sewage treatment
plants, and atmospheric deposition. High nutrient loads support algal blooms, which produce
anoxic conditions in the Bay. The anoxic portion of the Bay has steadily increased in size and
duration and is reducing the amount of suitable habitat for crabs. Declining habitat area increases
intraspecies competition. The area available for blue crab fishing compresses and commercial
fishing suffers due to the high mortality of crabs retained in pots in anoxic and hypoxic areas.
Strategy 6.1
The 1987 Chesapeake Bay Agreement (Chesapeake Executive Council, 1987) committed
the signatories of Maryland, Virginia, Pennsylvania, and the District of Columbia, to "achieve by
the year 2000 at least a 40 percent reduction of nitrogen and phosphorous entering the mainstem
Chesapeake Bay." Oxygen content goals for the Bay are also recommended.
Actions
6.1.1 The jurisdictions will implement tributary strategies to achieve the goal of 40%
nutrient reduction to the Chesapeake Bay mainstem by the year 2000. Major goals
outlined by the tributary strategies include:
Maryland:
* Upgrade 50 wastewater treatment plants to control nitrogen and
phosphorus discharges.
* Encourage farmers to implement nutrient management plans and
plant cover crops.
Pennsylvania:
* Implement nutrient control efforts on the state's farm lands.
* Fence hundreds of miles of streams to keep livestock out.
District of Columbia:
* Upgrade Blue Plains wastewater treatment plant, the greatest
source of nutrients from the District.
Blue Crab Management in Chesapeake Bay 69
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* Control combined sewer overflow to reduce the frequency of
overloads.
* Control additional runoff at construction sites, new development,
public education, and habitat restoration.
Virginia:
* Present a nutrient reduction strategy for Virginia's portion of the
Potomac River to the General Assembly by January 1, 1997.
* Present nutrient reduction strategies for the Rappahannock, York,
and James Rivers to the General Assembly by January 1, 1998.
Implementation: 2000
6.1.2 Baywide dissolved oxygen goals for selected Chesapeake Bay species, including
blue crab, are recommended as follows1:
a. All waters of Chesapeake Bay and its tidal tributaries should
contain a minimum of 1.0 mg/L dissolved oxygen at all times;
b. all waters above pycnocline of Chesapeake Bay and its tidal
tributaries should contain a monthly average of 5.0 mg/L dissolved
oxygen; and
c. dissolved oxygen concentrations between 1.0 and 3.0 mg/L should
not occur for longer than 12 hours and the interval between
excursions of dissolved oxygen between 1.0 and 3.0 mg/L should
be at least 48 hours throughout Chesapeake Bay and its tidal
tributaries.
The jurisdictions will consider the above recommendations when reviewing their state
standards. Juvenile blue crabs may be less tolerant of hypoxic conditions and the above
recommendations should be evaluated specifically for juvenile blue crabs.
Implementation: Recommendations in effect upon adoption of this plan.
Problem 6.2: Submerged Aquatic Vegetation and Intertidal Wetlands
Shoreline development that reduces shallow water habitat, heavy boat traffic, crab
scraping, and clam dredging all contribute to local destruction of submerged aquatic vegetation
(SAV). Crab scraping in Virginia is restricted to hauling by hand and hard crab bycatch is illegal.
In Maryland heavy scrapes with power winders are used during the early season to catch hard
crabs. Nutrient influx, as discussed in problem 6.1, and sediment runoff are responsible for
widespread declines in SAV throughout the Bay. The loss of SAV and intertidal wetlands has
resulted in the loss of blue crab habitat, particularly for crabs in juvenile and molting stages.
1 Adopted from Chesapeake Bay Dissolved Oxygen Goal for Restoration of Living Resources Habitats (Jordan et
al., 1992).
70 Blue Crab Management in Chesapeake Bay
-------
Strategy 6.2
The SAV Workgroup of the Chesapeake Bay Program's Living Resources Subcommittee
recommended strategies for SAV protection and restoration to benefit blue crab postlarval
settlement. The recommendations apply to the segments of Chesapeake Bay which are shaded and
stippled in Figure 3 and only in shallow water (2 meters deep or less), which is considered
potential SAV habitat (Batiuk et al. 1992). The Bay mouth (segment CBS) was not identified as
an SAV restoration area because there is very little potential SAV habitat there (Category D).
Table 4 in Action 6.2.2 includes information on recent SAV trends in each segment and
categorizes segments by condition. In general, areas where SAV area is currently increasing are
preferred as restoration sites over areas with recent declines. Causes for SAV declines in 1994
and 1995 are not well known. It remains unknown whether or not SAV should be planted in areas
with declining SAV populations. If recent SAV declines continue in segments from Category A,
they may have to be reclassified as Category B.
SAV restoration efforts focused in segments of Category B would provide the most
benefit to blue crab postlarval settlement habitat. Category B includes the lower reaches of four
major rivers on the Bay's western shore (Patuxent, Potomac, Rappahannock, and York rivers),
and two small tributaries on Maryland's lower eastern shore (Manokin and Big Annemessex
rivers). Nutrient and/or suspended sediment reduction efforts are needed in segments in Category
C before restoration efforts can be considered and include the lower James River and three other
small tributaries on Maryland's lower Eastern shore (Nanticoke, Wicomico, and Pocomoke
rivers). However, water quality in these segments can also be influenced by activities in segments
up-river and up-Bay.
The Chesapeake Bay Program is committed to, "achieve a net gain in SAV distribution,
abundance, and species diversity in the Bay and tidal tributaries over present populations"
(Chesapeake Executive Council, 1990). The Bay jurisdictions will maintain a priority status on
protection of SAV and intertidal wetlands.
Actions
6.2.1 The Chesapeake Bay jurisdictions will work to restore SAV to their historic levels.
Chesapeake Bay Program restoration goals and targets for SAV (CBP, 1993) are
as follows:
Tier I Goal Restore SAV Baywide to 114,000 total acres in areas
known to have been inhabited by SAV from 1971 to 1990.
The goal is to achieve this recovery by 2005.
Tier II Target Restore SAV to all shallow water areas delineated as
existing or potential SAV habitat down to the 1 meter depth
contour. Total restoration area: to be determined.
Tier III Target Restore SAV to all shallow water areas delineated as
existing or potential SAV habitat down to the 2 meter depth
contour. Potential restoration area: 611,000 acres.
Blue Crab Management in Chesapeake Bay 71
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Implementation:
Tier I: Ongoing
Tier II: 2005 or following full implementation of Tier I
Tier III: Following full implementation of Tier II
6.2.2. Segments of Chesapeake Bay for SAV protection and restoration which would
benefit blue crab postlarval settlement in areas 2 meters deep or less are identified.
Segments and recommended actions are provided as protection and restoration
goals and should also be reviewed when evaluating proposed activities which
would cause physical disruption or degradation of water quality in areas 2 meters
deep or less. Recommended actions are based on a decision matrix provided in
Appendix B. Segments and recommendations are as follows:
72 Blue Crab Management in Chesapeake Bay
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Table 4. Strategies for SAV Restoration and Protection for Postlarval Blue Crab Settlement
CBP
Segment'
Segment Name
(see Figure 3 for map of
segments)
1994 SAV acres
(% of Tier I
goal)1
1994 %
\VQ Goals
Met3
Trends in SAV area
Recommended Action: Protect existing SAV and maintain water quality (Category A)
CBS
EE3
CB6
WE4
CB7
Lower Central
Chesapeake Bay
Tangier Sound
Western Lower
Chesapeake Bay
Mobjack Bay
Eastern Lower
Chesapeake Bay
8,727 (56%)
11,301 (72%)
1,463 (76%)
11,343 (78%)
9,259 (81%)
80%
100%
80%
100%
100%
SAV area up 1 978- 1 992, declined
1993-1995
SAV area up 1 978- 1 993, declined
in 1994 and 1995
SAV area up 1 978- 1 993, declined
in 1994 and 1995
SAV area stable since 1 991
SAV area up 1978-1993, declined
in 1994 and 1995
Recommended Action: Protect existing SAV, maintain water quality, and restore SAV where feasible
(Category B)
LEI
LE2
ET8
ET9
LE3
LE4
Lower Patuxent River
Lower Potomac River
Manokin River
Big Annemessex R.
Lower Rappahannock
Lower York River
0 (0%)
345 (49%)
165 (25%)
400 (45%)
485 (11%)
193 (25%)
100%
100%
80%
100%
100%
100%
Few propagules present?
SAV increased 1992-95
SAV up & down since 1985
SAV area stable since 1 99 1
SAV area up 1 984- 1 993, declined
in 1994 and 1995
SAV increased 1991-95
Recommended Action: Improve water quality, then restore SAV where feasible (Category C)4
LE5
ET6
ET7
ET10
Lower James River
Nanticoke River
Wicomico River
Pocomoke River
15(38%)
0 (0%)
0 (0%)
0 (0%)
40%
40%
60%
40%
SAV increased 1993-95
No SAV mapped, 1978-95
No SAV mapped, 1978-95
No SAV mapped, 1978-95
1 SAV in other areas of Chesapeake Bay are also valuable as habitat for juvenile and adult crabs.
2 Number of acres of SAV mapped in 1994 (1994 acres as a % of the Tier I goal, Orth et ai \ 995).
3 % of 4 or 5 water quality goals for SAV that were met or borderline in 1994.
4 One segment in Category D not listed because it is not suitable for SAV restoration (see text).
Blue Crab Management in Chesapeake Bay 73
-------
Implementation: Recommendations for restoration must be balanced with other
restoration priorities and is contingent upon funding. Recommendations for protection of
existing SAV are in effect upon adoption of this plan.
6.2.3 The Bay jurisdictions will cooperatively prepare a report that links land use
activities in the Chesapeake Bay watershed and human activities within
Chesapeake Bay to negative impacts on fish and shellfish habitat. The document
may be used by permitting agencies, local governments, citizens, and commercial
and recreational harvesters and will be accompanied by an extensive literature
review section and compendium of laws and regulation pertaining to fish and
shellfish habitat.
Implementation: 1997
6.2.4 Maryland will consider limits on scraping for hard crabs in the early crabbing
season and maximum weight limits for crab scrapes.
Implementation: 1997
Problem 6.3: Toxics
The blue crab appears to be a resilient species. Its migratory nature and short life span
make it less susceptible to bioaccumulation of contaminants. Toxicology studies in Baltimore
Harbor and the Elizabeth River, the two most heavily polluted areas of the Bay, found minimal
accumulation of toxins in tissues of blue crabs. Once toxins are allowed to accumulate, their
effects are difficult or impossible to reverse. Blue crabs could be affected by the loss of benthic
foods and/or toxins may accumulate beyond some threshold that exceeds the crab's level of
tolerance. Blue crabs are most sensitive to toxics during their larval stages.
Strategy 6.3
The Chesapeake Bay Program will continue its commitment to the goal of, "a Chesapeake
Bay free of toxics by reducing or eliminating the input of chemical contaminants from all
controllable sources to levels that result in no toxic or bioaccumulative impact on the living
resources that inhabit the Bay or on human health" (CBP, 1994b).
Actions
6.3.1 Regions of concern will be identified with criteria set by the Chesapeake Bay
Basinwide Toxics Reduction and Prevention Strategy (CBP, 1994b). Within
regions of concern the sources and amounts of pollution will be determined,
control methods will be explored and implemented, and important habitats within
the area and land uses with negative effects will be identified.
Implementation: Ongoing
74 Blue Crab Management in Chesapeake Bay
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Messick, G. A. 1994. Hematodinium perezi infections in adult and juvenile blue crabs, Callinectes
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Metcalf, K. and R. Lipcius. 1992. Relationship of Habitat and Spatial Scale with Physiological
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Millikin, M. and A. Williams. 1984. Synopsis of biological data on the blue crab,
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Montane, M., R. Lipcius, J. Haner and M. Seebo. 1994. A field study of the population dynamics
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Officer, C, R. Biggs, J. Taft, L. Cronin, M. Tyler and W. Boynton. 1984. Chesapeake
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Orth, R. and K. Moore. 1983. Chesapeake Bay: An unprecedented decline in submerged
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Orth, R. and K. Moore. 1984. Distribution and abundance of submerged aquatic vegetation
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86 References
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Appendix A. Schedule for Reviewing and Updating Chesapeake Bay Fishery
Management Plans*
SPECIES
Blue C'rab
Striped Bass
Summer Flounder
Weakfish/Spotted Seatrout
Shad & Hemng
Oysters
Bluefish
American Eel
Horseshoe Crabs
Atlantic Croaker/Spot
Black Drum
Black Sea Bass
Red Drum
Spanish/King mackerel
REVIEW SCHEDULE
1 989-adopted
1997 -revised
1 989- adopted
1 0/95 - reviewed
1 0/97- Amend. #1
1991 -adopted
4/96 - reviewed
6/97 - Amend. #1
1 990- adopted
4/96 - reviewed
1 989 - adopted
7/95 - reviewed
12/97 - Amend. #1
1989 -adopted
1 993 - reviewed
1 994 - revised
1990 -adopted
7/95 - reviewed
1 997 - amend
1991 -adopted
1 0/96 - reviewed
1 994 - adopted
1991 -adopted
1 0/96 - reviewed
1993 -adopted
1 997 - review
1996 -adopted
1 993 - adopted
1 997 - review
1994 -adopted
1 998 - review
UPDATE SCHEDULE
Annually
Annually
Annually
Annually
1999
2001
1996
1998
1998
2000
1999
2002
1999
2002
1998
2001
2000
2003
1998
2001
2000
2003
2001
2004
* The review and update schedule will be adjusted as necessary depending on the species-specific needs and/or issues.
Appendix A
87
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Appendix B. Decision Matrix Used to Make Recommendations in Action 6.2.2
Decision matrix used to make recommendations in Action 6.2.2 to maintain and increase
the amount of SAV in each area of high postlarval blue crab settlement.
Category
A
B
C
D
Recent SAV
area
Moderate to
high
Low (50% or
less of Tier I"
goal met)
Low
Low
Potential SAV
area
Moderate to
High
Moderate to
High
Moderate to
High
Low
Recent water quality
for SAV growth
Adequate (80% or
more of goals met or
borderline)
Adequate
Inadequate (less than
80% of goals met or
borderline)
Adequate or
inadequate
Recommended action
Protect SAV and
maintain water quality
Protect SAV, maintain
water quality, restore
SAV where feasible
Improve water quality,
then restore SAV
where feasible
No action (Not listed in
Table 4,. Action 6.2.2,
for this reason)
"See Action 6.2.1 for Tier I goal.
Recommended actions in the above matrix are defined as follows:
• Protect SAV: Prevent physical disruption of SAV and potential SAV habitat, mainly by
avoiding disruptive activities or limiting them to areas outside SAV habitat or outside the
SAV growing season (CBP, 1995a).
• Maintain or improve water quality: All signatories of the 1987 Chesapeake Bay
Agreement (Chesapeake Executive Council, 1987) should implement the "tributary
strategies for nutrient reduction" called for in the 1992 Amendments to the Chesapeake
Bay Agreement (Chesapeake Executive Council, 1992), to reduce nutrient and sediment
runoff. More actions to reduce runoff are needed in areas that do not currently meet the
SAV habitat requirements than in areas that currently meet them.
• Restore SAV where feasible: This involves a series of linked actions, currently being
defined by the SAV Workgroup. They are based on successful restoration efforts in
Chesapeake Bay and elsewhere in the U.S. (Fonesca 1992; 1993). The first steps involve
assembling existing SAV and water quality monitoring data and collecting any additional
data needed, including sediment characteristics and potential for disturbance. Potential
areas for SAV planting should have historically supported SAV, but currently have little;
88 Appendix B
-------
have water quality and sediment characteristics adequate to support SAV; and have low
potential for disturbance. Results from pilot SAV planting projects are being reviewed to
refine these guidelines and add planting technique.
Appendix B 89
-------
APPENDIX C. LAWS AND REGULATIONS
Limited Entry:
Maryland Limited entry for all commercial crabbing licenses. No new tidal fish licenses will
be issued after April 1, 1996, after which, the state will evaluate the current license
structure and determine the number at which commercial licenses will be capped.
Virginia No crab dredge licenses will be issued to any new applicant after March 31, 1994,
until the number of licenses drops to 220 or below, as of December 10 of any year.
Crabbers who held crab pot licenses in 1995 were allowed to purchase licenses for
the same amount of pots in 1996. Applicants who did not hold a valid crab pot
license in 1995 must meet the following criteria to receive a license after 1995:
... List criteria here ...
Potomac Only Maryland and Virginia residents may commercially crab. Maximum of 593
commercial crab pot licenses; number of pots selected for on license cannot be
changed later. Only one license per boat.
Non-Commercial License
Virginia
Maryland
Potomac
River
-none required for up to 2 crab pots
-license required for up to 5 crab pots
-none required
-none required
90 Appendix C
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Minimum Size Limit:
Peelers
Soft Crabs
Male, Hard
Crabs
Females,
Mature Hard
Crabs
Female,
Immature
Hard Crabs
Virginia
No
minimum
size
3.5 inches
5 inches
No
minimum
size •
5 inches
Maryland
3 inches
3.5 inches
5 inches
No
minimum
size
5 inches
Potomac
3 inches
3.5 inches
5 inches
No
minimum
size
5 inches
Tolerance
MD&VA-lO/bushel
VA - 35/barrel
Potomac - 4/bushel and
10/barrel
MD and Potomac -
Sponge crabs prohibited
VA - Minimum
tolerance for brown and
black sponge crabs
VA- 10/bushel and
35/barrel
Creel Limit:
Maryland
Virginia
Potomac
All recreational crabbers -
Unlicensed sport crabbers
Licensed sport crabbers -
Unlicensed sport crabbers
Licensed sport crabbers -
1 bushel/person/day
2 bushels/boat/day
1 bushel/person/day
2 dozen peelers/person/day
No limit
1 bushel/person/day
3 dozen soft or peelers/person/day
No limit
Appendix C
91
-------
Harvest Quotas:
Maryland None in effect
Virginia Winter dredge fishery 20 barrels/boat/day
(Dec. 1 -March 1)
Spring crab pot fishery 51 bushels/boat/day
(April 1 - May 31) 17 barrels/boat/day
Potomac None in effect
By-catch Restrictions:
Maryland Sponge crabs prohibited; imported sponge crabs must be legally harvested from
the state of harvest and accompanied with a bill of landing.
Virginia Possession of hard crabs prohibited while scraping. Minimum tolerance for harvest
of brown and black sponge crabs.
Potomac Possession of sponge crabs, spawn crabs, blooming females, mother crabs, or
females from which the egg pouch or bunion has been removed is prohibited.
Gear Restrictions:
Maryland Crab Pots
-Cubic and rectangular pots permitted
-Cubic pots cannot exceed 24 inches on any side
-Rectangular pot size limit 12 inches x 24 inches x 48 inches
-All hard crab pots must be wire mesh 1.5 inches by 1.5 inches or greater
-All peeler pots must be wire mesh at least 1.0 inches by 1.0 inches; pots with
mesh 1.5 inches by 1.5 inches or greater are not defined as peeler pots
-One 2 5/16 inches and one 2 3/16 inches cull ring in the top or side panels of all
hard crab pots, with mesh between 1.5 inches by 1.5 inches and 2.0 inches by 2.0
inches; may be closed when fishing for peelers
-Must be marked with a buoy attached to the pot and clearly visible on the surface
and marked with ID number with 2 inches letters
-Commercial limit 300 pots per licensee, additional allocations for up to two crew
members, up to 900 pots per boat
-Shoreline property owners limit 2 pots per property from piers or poles within
100 yds. of shore for personal consumption only and must be marked with name
and address
92 Appendix C
-------
-Peeler pots may only be baited with one male hard crab and enough food for the
male crab
Trotlines
-Unlicensed sport crabber limit 1000 feet; not to exceed 2000 feet per vessel
Maryland -Length measured along the baitline
-May not be set within 100 feet of another trotline
Scrapes or Dredges
-Total width may not exceed 60 inches
-Teeth prohibited
-Diver, chain or other device to hold it to the bottom prohibited
-Flat plate on scraping bar prohibited
-Limit 2 scrapes or dredges per engine-powered boat, only one overboard
-Scrapes may not be affixed to each other
Bank Traps
-Enclosure no more than 4 feet long and 4 feet wide
-Limit 1 row of hedging no more than 75 feet long
-Hedging may not exceed 1/3 the distance across the body of water in which its
placed
Channel Pounds
-Enclosure no more than 8 feet long and 4 feet wide
-Limit 2 rows of hedging no more than 100 feet long
-Hedging may not exceed 1/3 the distance across the body of water in which its
placed
Bank Traps and Channel Pounds
-Must be spaced 100 yards apart
-A 12 inches air space from surface of water at mean high tide required
-Must be marked with name and license number with 2 inches letters
Seines
-Maximum length 50 feet
-Must be hauled up in water
Collapsible Traps
-Limit 10 traps or rings for noncommercial crabbers from shore, bridge or pier
-Limit 25 per vessel for noncommercial crabbers
-Flat bottom and not more than 4 sides, each < 1 ft2
-Must have manual tension on the closing mechanism
-Those not attached to structures must be marked with a buoy and owner ED
-Cannot be set within 100 feet of trotline
SCUBA Diving
-Capture of crabs using diving apparatus prohibited
Virginia Crab pots
-Wire or thread mesh 1.5 inches or greater
-Crab pot buoys must display assigned number
Appendix C
93
-------
-One 25/16 inches and one 23/16 inches cull ring in upper parlor on opposite
sides; the 25/16 inches cull ring may be obstructed within commercial dredge
boundaries in the Bay, and in Pocomoke and Tangier Sounds
- Limit 300 pots/person in tributaries; limit 500 pots/person in Bay mainstem; limit
500 pots total per person in all tidal waters.
-Unlicensed sport crabber limit 2 pots
-Licensed sport crabber limit 5 pots
-Recreational pots must display "R" on buoys
Peeler Pots
-Wire mesh, no minimum mesh size
-Bait only with live adult male hard crabs; food for male crabs in peeler pots
prohibited
-Baiting prohibited Sep. 16 to May 14
-No cull ring required
-Limit 400 pots/vessel April-June
-Limit 400 pots/person July-Nov.
-Limit 2 licensees per boat
Trot Line
-Sport crabber limit 300 feet
Scrapes
-Mouth not to exceed 4 feet overall
-No teeth on bar
-Haul by hand only
-Limit 2 scrapes/boat overboard at one time
-No tolerance for hard crabs
Dredges
-Inside mouth not to exceed 8 feet
-Teeth permitted
-When 2 or more dredges are fixed together, total width may not exceed 16 feet
-Use of more than 2 dredges at one time prohibited
-One dredge on each side of boat or two dredges joined over stern
-Hydraulic methods to dislodge crabs prohibited
Rakes. Dredges, and Scrapes (except hand rakes)
-May not be used on seaside of Eastern Shore in water less than 4 feet at mean low
tide
Traps/Pounds
-Four 1.5 inches cull rings in retention box
Potomac -Crab pots, trotlines, dip nets, patent trotlines, and peeler traps permitted
-Minimum mesh size for hard crab pots, 1 '/£"
-One 2 5/16 inches cull ring required in exterior panel of upper chamber of all crab
pots, may be closed May and June
-Second cull ring, 2 3/16", required in all pots
94 Appendix C
-------
-Two 1 Vz" cull rings required in peeler pots
-Four 1 '/21' cull rings required in peeler traps (pounds)
-Dredges prohibited scrapes
-Culling container required on all vessels; must be cleared before leaving area of
crabbing
-Noncommercial limits: 1 pot/person/day; 1000'trotline/person; unlimited
collapsible traps; dip nets allowed
Area Restrictions:
Maryland -Crab pots permitted in waters of Chesapeake Bay proper, Pocomoke Sound and
waters of Somerset County in Tangier Sound
-Crab pots prohibited in all other bays, sounds, and tributaries; in less than 4 feet of
water except in designated areas; and within 200 yards of a public beach May 1 -
Sept. 30
-Crab scrapes prohibited in portions of Choptank River, Little Choptank River, St.
Mary's River, Calvert Bay, Smith Creek, and all submerged lands leased for oyster
cultivation.
-Minimum distance of 100 feet between trot lines
-Bank traps/crab pounds only permitted in Somerset and St. Mary's Co. and waters
surrounding Eastern Neck Island
-One stake may be set in riparian waters by the respective landowner or leasee
marking site for bank traps or channel pounds between March 1 and March 14.
-After March 15, 8 a.m., any licensee may stake sites for bank traps and pounds.
-Bank traps and hedging must be in place by May 1 to maintain stake, and bank
traps and pounds must be removed by Dec. 1.
-Hand-drawn net scrapes only permitted in waters of Queen Anne's Co. and Kent
Co.
Virginia -Minimum distance of 100 yards between crab traps or crab pounds
-Crab pots prohibited in marked navigational channels
-Dredges prohibited in rivers, estuaries, inlets, or creeks except seaside of
Accomack and Northampton counties
-Unlawful to take crabs for resale from lower Bay crab sanctuaries and Pretty Lake
sanctuary June 1 to Sept. 15, inclusive
-Fixed fishing devices prohibited within 300 yards of Chesapeake Bay Bridge
Tunnel
-Crab scraping permitted in Tangier Island crab scrape sanctuary, unlawful to set
crab pots or take hard crabs by any gear
-Dredges prohibited upriver of Hampton Roads Bridge Tunnel
Appendix C 95
-------
Potomac -Crab pots prohibited within 200 yards of any public beach May through
September
-No pots or floats in federally marked navigation channels
Season/Time Restrictions:
Maryland -Closed season for commercial and recreational crabbing December 1 to March 31
-Closed season for crab scrapes Oct. 31 to April 14
-Scraping from April 15 to Oct. 30 one hour before sunrise to sunset
-Commercial crabbing with crab pots, bank traps, channel pounds, collapsible
traps, net rings, handlines, or dipnets prohibited 5 p.m. to 4:30 a.m. and trotlines
between 5 p.m. and 3 a.m.
- Commercial crabbing prohibited on either Sunday or Monday except holidays;
harvester must display the letters SUN or MON on port side of vessel near stern to
identify the chosen day off.
-Recreational crabbing prohibited between 5 p.m. and 5:30 a.m. in Chesapeake
Bay or sunset to 5:30 a.m. in tidal Bay tributaries. No limits from shore, bridges,
or piers.
-Recreational crabbing with collapsible traps, net rings, and trotlines is prohibited
on Wednesdays.
Virginia -Crab dredging prohibited April 1 to November 30
-Crab dredging prohibited on Saturday
-Commercial crabbing prohibited on Sunday (except peeler traps or floats, pens or
onshore facilities for soft crab shedding)
-Commercial crabbing prohibited between sunset and 3 hours before sunrise
-Crab dredging prohibited sunset to sunrise
-Crab pots (hard and peeler) prohibited Dec. 1 - March 31
-Crab traps/pounds must be removed by December 31
-Crabbing prohibited June 1 to Sep. 15 in lower Bay crab sanctuaries
Potomac -Commercial crabbing prohibited between sunset and one hour before sunrise
-No closed season
-Noncommercial, same as commercial
96 Appendix C
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Appendix D. Glossary of Terms and Acronyms
Anoxia: No oxygen.
Apron: Hard flap underneath a crab that protects the abdomen.
Benthos: Community of organisms associated with the bottom, such as clams that live in the
sediments.
Bivalve: Mollusk with two shells connected by a hinge (ex: clams, oysters).
Buckrams: Crabs that have recently shed, but have not grown into their new shell. Buckrams are
light weight and yield less meat than fully developed hard crabs.
Catchability (q): The average portion of a fish stock that a unit of gear (i.e. one crab pot) is
capable of catching. Catchability is a measure of the catch efficiency of the gear.
Catch Per Unit Effort (CPUE): The number or weight (biomass) of crabs caught per unit of
gear. CPUE may be influenced by changes in crab abundance. For example, higher abundance
means more crabs are available to be caught.
CBP: Chesapeake Bay Program
CBSAC: Chesapeake Bay Stock Assessment Committee
Cradle: When a male crab carries a female peeler crab just prior to maturity so that mating can
occur immediately after the hard shell is molted.
Cull rings: Plastic rings worked into the mesh of a crab pot and large enough in diameter to allow
small, sublegal crabs to escape.
Exploitation (u): The fraction of a population that is removed by fishing over the course of a
year (also accounts for any concurrent natural mortality). Exploitation may also be expressed as a
percentage of the population.
Fmtl: The level of fishing mortality (F) at which the greatest poundage (yield) is seen from the
fishery. Ynax is the biological reference point used to define overfishing.
F,0./.: Fishing mortality rate that allows for at least 10% of the spawning stock to escape the
fishery to reproduce. F10% is measured as 10% of the estimated spawning stock under unfished
conditions.
Fishery dependent: Data obtained from commercial or recreational harvest.
Appendix D 97
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Fishery Independent: Data collected from an independent survey rather than from commercial
or recreational harvest.
Fishing mortality (F): a measure of the rate at which blue crabs are removed from the
population by the fishing activities of man. If F is constant over time, harvest will be greater
during times of high abundance and less during times of low abundance. F= Z-M.
FMP: Fishery Management Plan
Fully exploited: When a fishery is fully utilized and additional harvest is discouraged to avoid
overfishing. In an underutilized fishery, additional harvest does not threaten the population.
Ghost pots: Crab pots lost to storms or left abandoned at the end of the fishing season.
Growth overfishing: The losses in weight (biomass) from harvest and natural mortality exceed
the gain in weight due to reproduction and growth. Growth overfishing results in a net loss of
crab poundage from one year to the next, which is characterized by a decreasing proportion of
older and larger crabs in the catch.
Hypoxia: Low oxygen.
Insemination rate: The proportion of females in the population that successfully mated during
their terminal molt.
Instar: Crabs increase shell size when old shells are molted (shed) and new shells are soft and
expandable. Instar is the hard shell stage between molts when a crab is not increasing in size.
Maximum Sustainable Yield (MSY): The largest average catch or yield that can continuously
be taken from a stock under existing environmental conditions. The MSY for Chesapeake Bay
blue crabs is the greatest poundage of crabs that can be removed from the Bay without reducing
the capacity for the crabs to replenish the population to the same level for harvest in future years.
MDNR: Maryland Department of Natural Resources
Megalopae: Blue crab postlarvae.
Natural mortality (M): The rate of removal of crabs from a population due to natural death
(disease, predation, old age).
Nominal fishing effort (f): Fishing effort measured in time (days fished) and number of gear units
(ie. number of pots).
98 Appendix D
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Optimum yield (OY): A modified MSY that considers economic, social or ecological issues. OY
is frequently used as justification for harvest exceeding MSY.
Overcapitalization: When harvesters invest in and deploy amounts of fishing gear greater than
what is necessary to harvest a given amount of crabs. For example, when a harvester enters the
fishery using 100 pots to catch 20 bushels of crabs, and later increases his investment to 200 pots
but still catches only 20 bushels of crabs.
Passive gear: Gear that requires the animal to enter voluntarily (as opposed to active gears such
as trawls and dredges which must move to trap animals and prevent them from escaping.
Plankton: Small or microscopic algae and organisms associated with surface water and the water
column.
ppt: Parts per thousand.
Recruitment: Entry of crabs from one size class to the next class higher. May also refer to entry
of crabs into the population as they are spawned and develop into juvenile crabs, or entry of
juvenile crabs into the mature population as they grow.
Recruitment overfishing. The rate of fishing above which recruitment to the fishable stock is
reduced. Recruitment overfishing is characterized by a reduced spawning stock and generally very
low production of young year after year.
SAV: Submerged Aquatic Vegetation. Also called grass beds.
Size class: Crabs within close size range of each other, and presumably close in age.
Soft shell phase: Immediately after a crab molts when the new shell is soft and expandable.
Spawning stock: All females that survive natural and fishing mortality to reproduce.
Spermatheca: A receptacle on the underside of female crabs for receiving and holding sperm for
use later to fertilize eggs.
Terminal molt: Last molt in female blue crabs that precedes maturity.
Total mortality (Z): Natural mortality plus fishing mortality.
Year class: see size class.
Zoeae: Blue crab larvae
Appendix D 99
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Appendix E. Plan Developers and Contributors
Blue Crab Fishery Management Plan Workgroup
Dorothy Leonard, Co-chair, Maryland Department of Natural Resources (MDNR)
Jack Travelstead, Co-chair, Virginia Marine Resources Commission (VMRC)
Nancy Butowski, Asst. chair, MDNR
George R. Abbe, Academy of Natural Sciences
Wayne O. Abbott, Citizen
William E. Abbott, Citizen
Jack C. Brooks, Dorchester Seafood
K. A. Carpenter, Potomac River Fisheries Commission
James Casey, MDNR
Jim Casey, Casey Seafood, Inc.
Eddie Crockett, Citizen
Jeff Crockett, Tangier Watermen's Association
Eugene Cronin, Citizen
James O. Drummond, Citizen
Bonnie Fitch, Citizen
John W. Freeman, Citizen
C. M. Frere, Maryland Natural Resources Police
William Goldsborough, Chesapeake Bay Foundation
John Graham, Citizen
Wade Harding, Citizen
Edward Houde, Chesapeake Biological Laboratory
Michael Howard, Natural Resources Police
W. Pete Jensen, MDNR
Anne Lange, National Marine Fisheries Service (NMFS)
Romauld Lipcius, Virginia Institute of Marine Sciences (VIMS)
Doug Lipton, Sea Grant, University of Maryland Extension Service
Andrew J. Loftus, Natural Resources Consultant
William MacDonald, Chesapeake Bay Commission
Larry Minock, Virginia Council on the Environment
Michele Monti, Alliance for the Chesapeake Bay
Bill Moore, Citizen
Peter Nixon, Citizen
Richard Novotny, Maryland Saltwater Sport Fishermen's Association
Ed O'Brien, Maryland Charterboat Association
Ira Pamer, Citizen
Beverly Sauls, MDNR
Vernon O. Setterholm, Citizen
100 Appendix E
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Larry Simns, Maryland Watermen's Association
Bobby Taylor, Citizen
Mike Thorne, Citizen
Andrew Tolley, Toddville Seafood Inc.
Jack Travelstead, Virginia Marine Resources Commission (VMRC)
William Van Heukelem, Horn Point Environmental Laboratory, University of Maryland
Jacques van Montfrans, VIMS
Mary Roe Walkup, Citizen
Louis Whittaker, Sea Products, Inc.
Woody Zembar, Eastern Shore Seafood Co.
Appendix E 101
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Chesapeake Bay Stock Assessment Committee, Technical Subcommittee
Louis Rugolo, Subcommittee Chair, MDNR
Anne Lange, National Marine Fisheries Service (NMFS)
Karen Knotts, MDNR
Victor Crecco, Connecticut Department of Environmental Protection
Mark Terceiro, NMFS, Southeast Fisheries Science Center
Chris Bonzek, VIMS
Cluney Stagg, MDNR (formerly)
Robert O'Reilly, VMRC
Douglas Vaughan, NMFS, Southeast Fisheries Science Center
Bi-State Blue Crab Advisory Committee, Technical Workgroup
Ann Swanson, Workgroup Chair, Chesapeake Bay Commission
L. Eugene Cronin, Citizen
Michael Fogarty, Chesapeake Biological Laboratory, University of Maryland
M. Elizabeth Gillelan, National Oceanic and Atmospheric Administration (NOAA)
Edward Houde, Chesapeake Biological Laboratory, University of Maryland
James Kirkley, Virginia Institute of Marine Sciences (VIMS)
Rom Lipcius, VIMS
Douglas Lipton, University of Maryland
John R. McConaugha, Old Dominion University
William D. MacDonald, Chesapeake Bay Commission
Robert J. Orth, VIMS
Leonard Shabman, Virginia Polytechnic Institute
Willard Van Engel, VIMS
Jacques van Montfrans, VIMS
Roy Insley, Virginia Marine Resources Commission (VMRC)
Harley Speir, Maryland Department of Natural Resources (MDNR)
102 Appendix E
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Chesapeake Bay Program
The Chesapeake Bay Program is a unique regional partnership leading and
directing restoration of Chesapeake Bay since 1983. The Chesapeake Bay
Program partners include the states of Maryland, Pennsylvania, and Virginia;
the District of Columbia; the Chesapeake Bay Commission, a tri-state legislative
body; the U.S. Environmental Protection Agency (EPA), which represents the
federal government; and participating citizen advisory groups.
In the 1987 Chesapeake Bay Agreement, Chesapeake Bay Program partners set
a goal to reduce the nutrients nitrogen and phosphorus entering the Bay by 40%
by the year 2000. In the 1992 Amendments to the Chesapeake Bay Agreement,
partners agreed to maintain the 40% goal beyond the year 2000 and to attack
nutrients at their source—upstream in the tributaries. The Chesapeake
Executive Council, made up of the governors of Maryland, Pennsylvania, and
Virginia; the mayor of Washington, D.C.; the EPA administrator; and the chair
of the Chesapeake Bay Commission, guided the restoration effort in 1993 with
five directives addressing key areas of the restoration, including the tributaries,
toxics, underwater bay grasses, fish passages, and agricultural nonpoint source
pollution. In 1994, partners outlined initiatives for habitat restoration of
aquatic, riparian, and upland environments; nutrient reduction in the Bay's
tributaries; and toxics reductions, with an emphasis on pollution prevention.
The 1995 Local Government Partnership Initiative engages the watershed's
1,650 local governments in the Bay restoration effort. The Chesapeake
Executive Council followed this in 1996 by adopting the Local Government
Participation Action Plan and the Priorities for Action for Land, Growth and
Stewardship in the Chesapeake Bay Region, which address land use
management, growth and development, stream corridor protection, and
infrastructure improvements. A 1996 riparian forest buffers initiative furthers
the Bay Program's commitment to improving water quality and enhancing
habitat with the goal of increasing riparian buffers on 2,010 miles of stream and
shoreline in the watershed by the year 2010.
Since its inception, the Chesapeake Bay Program's highest priority has been the
restoration of the Bay's living resources—its finfish, shellfish, bay grasses, and
other aquatic life and wildlife. Improvements include fisheries and habitat
restoration, recovery of bay grasses, nutrient reductions, and significant
advances in estuarine science.
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U.S. Environmental Protection Aga
Region III !r.Fc>: ration Resource
Center (jF/.'sji}
Philadelphia, FA T"i07
U.S. Environmental Protection Agency
Chesapeake Bay Program Office
410 Severn Avenue
Annapolis, MD 21403
1-800-YOUR BAY
www.epa.gov/chesapeake
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