Chesapeake Executive Council
903R88113
Stock Assessment
Plan
Chesapeake
Bay
Program
Agreement Commitment Report
TD
225
.C54
S861
copy 2
July 1988
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Stock Assessment Plan
An Agreement Commitment Report from
the Chesapeake Executive Council
U.S. Environmental Protection Agenqf
Region 111 Information Resourca
Center (3PM52)
841 Chestnut Street
Philadelphia, PA 19107
Annapolis, Maryland
July 1988
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ADOPTION STATEMENT
We, the undersigned, adopt the Chesapeake Bay Stock Assessment Plan, as developed by
the Chesapeake Bay Stock Assessment Committee, in fulfillment of Living Resources Commit-
ment Number 2 of the 1987 Chesapeake Bay Agreement:
"...by July, 1988, to develop, adopt and begin to implement a Bay-wide plan
for the assessment of commercially, recreationally and selected ecologically
valuable species."
The Plan proposes improved means of assessing stocks of finfish and shellfish in the
Chesapeake Bay. It identifies outstanding data needs for stock assessment models for Bay
fisheries. Recommendations include improved ways to collect catch, effort, and biological data
from commercial and recreational landings, in addition to long- term surveys for estimating relative
abundance of important species in all regions of the Bay and its tributaries. There are
recommendations in the Plan for studies of early life stages designed to examine natural and
human-caused sources of mortality and to investigate biological effects of pollution, habitat loss,
and disease.
The data collected in the recommended trawl and seine surveys will be used by the stock
assessment groups to develop short-term management related information and by monitoring
groups to track long-term trends. These stock assessments will be used in the development of
fisheries management plans due for thirteen species between July 1989 and 1992.
We agree to support the Plan's recommendations for new efforts to collect basic, short- and
long-term data, consistent Bay-wide, that are essential for stock assessment and monitoring. We
recognize the need to commit financial and human resources to the task of developing and
implementing the recommendations of the plan. Finally, we direct the Chesapeake Bay Stock
Assessment Committee to prepare annual reports detailing the progress made in implementing the
Plan's recommendations.
For the Commonwealth of Virginia
For the State of Maryland
For the Commonwealth of Pennsylvania
For the United States of America
For the District of Columbia
For the Chesapeake Bay Commission
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FOREWORD
We, the undersigned, adopt the Chesapeake Bay Stock
Assessment Plan, as developed by the Chesapeake Bay Stock
Assessment Committee, in fulfillment of the living resources
commitment:
"by July 1988 to develop, adopt and begin to implement
a Bay-wide plan for the assessment of commercially,
recreationally and selected ecologically valuable
species."
The Plan proposes improved means of assessing stocks of
finfish and shellfish in Chesapeake Bay. It identifies
outstanding data needs for stock assessment models for Bay
fisheries. Recommendations include improved ways to collect
catch, effort, and biological data from commercial and
recreational landings in addition to long-term surveys for
estimating relative abundance of important species in all
regions of the Bay and its tributaries. There are
recommendations in the Plan for studies of early life stages
designed to examine natural and human-caused sources of
mortality and to investigate biological effects of
pollution, habitat loss, and disease.
The data collected in the recommended trawl and seine
surveys will be used by the stock assessment groups to
develop short-term management related information and by
monitoring groups to track long-term trends. Stock
assessment information will also be used in the development
of fisheries management plans, scheduled for completion for
13 species between July 1989 and 1992.
We agree to support the Plan's recommendations for new
efforts to collect basic, short and long-term data,
consistent Bay-wide, that are essential for stock assessment
and monitoring. We recognize the need to commit financial
and human resources to the task of developing and
implementing the recommendations of the plan. Finally, we
direct the Chesapeake Bay Stock Assessment Committee
annually to prepare reports detailing the progress made in
implementing the plan's recommendations.
111
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ACKNOWLEDGEMENTS
The development of this plan has been a cooperative effort of
the Chesapeake Bay Stock Assessment Committee (CBSAC) and its
coopted experts. The following scientists authored sections
of the Plan: Herb Austin, Erik Earth, Chris Bonzek, John
Boreman, Bess Gillelan, Dick Hennemuth, Marta Nammack, Mike
Prager, Louis Rugolo, and Cluney Stagg. Chapter 2 is an
edited version of the soon to be released Status of Stock
Knowledge report which was edited by Herb Austin and authored
by members of the CBSAC SOSK working group. The Plan was
edited by Erik Earth. Special thanks are due to Dick
Hennemuth, Bess Gillelan, and Verna Harrison for guiding the
Plan through the development and adoption process. The
remainder of the Committee assisted substantially through
their review and comment on the Plan. The membership of the
committee is as follows:
Members
Dick Hennemuth, Chairman, NOAA NEFC
John Boreman, NOAA NEFC
Bess Gillelan, NOAA EPO
Charlie Wooley, USFWS
Lou Rugolo, Vice-chairman, MD DNR
Steve Jordan, MD DNR
Brian Rothschild, UMCEES CBL
Herb Austin, VIMS
Jack Travelstead, VMRC
John McConaugha, ODU
G. P. Patil, PSU
Marta Nammack, DC DCRA
Alternates
Chris Bonzek, MD DNR
Cluney Stagg, CBL
Mark Chittenden, VIMS
Erik Earth, VMRC
Cynthia Jones, ODU
Marilyn Boswell, PSU
Coopted Experts
Nick Bolgiano, PSU
Jim Colvocoresses, VIMS
Gerard DiNardo, UMCEES CBL
Ed Houde, UMCEES CBL
Pete Jensen, MD DNR
Mike Prager, ODU
Harley Speir, MD DNR
Kevin Summers, VERSAR
Liasons
Betty Bauereis, CAC
Kent Mountford, EPA
Bill Rickards, STAC
IV
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TABLE OF CONTENTS
PAGE
FOREWORD iii
ACKNOWLEDGEMENTS iv
EXECUTIVE SUMMARY vii
I. Introduction - Fisheries Management and Stock
Assessment goals, objectives, and information
needs 1
II. Characteristics of Selected Chesapeake Bay
Fishery Species 5
American Shad 8
Black Drum 8
Bluefish 10
Blue Crabs 11
Croaker 12
Eel 13
Menhaden 14
Oysters 15
River Herrings 17
Red Drum 19
Spot 20
Striped Bass 21
Summer Flounder 22
Weakfish 24
White Perch 25
Yellow Perch 25
Other Ecologically Important Species 26
III. Approach to Stock Assessment 29
IV. The Data Collection Programs 35
Fishery Dependent Data - studying the harvests . . 35
Fishery Independent Data - surveying the
populations 48
Recruitment Process Studies 55
V. Implementation 59
RELATED READINGS 66
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LIST OF FIGURES
PAGE
Figure 1. Status of Stock Knowledge 7
Figure 2. Conceptual Relationships for
Fishery Models 31
Figure 3. Sample Fish Ticket 43
Figure 4. Sample Area and Gear Coding
for Fish Tickets 44
Figure 5. Sample Species Coding for
Fish Tickets 45
Figure 6. Flow of Activity and Responsibility
for Chesapeake Bay Stock Assessment 61
LIST OF TABLES
Table l. Common Gears for Fishery
Independent Sampling 49
Table 2. Additional Funding Requirements
to Fullfill Stock Assessment
Program Recommendations 65
VI
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EXECUTIVE SUMMARY
In recognition of the important values - economic,
recreational, ecological, aesthetic, symbolic - that are
attributed to Chesapeake Bay living resources, the 1987
Chesapeake Bay Agreement contains an entire category of
commitments related to restoring and protecting the Bay's
living resources. The Chesapeake Bay Stock Assessment Plan
responds to one of these commitments:
By July 1988, develop, adopt, and begin to implement a
Baywide plan for the assessment of commercially,
recreationally, and selected ecologically important species.
The Plan was developed by the Chesapeake Bay Stock
Assessment Committee, a federal/state committee sponsored by
the National Oceanic and Atmospheric Administration (NOAA).
Membership includes scientists and resource managers from
Maryland, Virginia, Pennsylvania, the District of Columbia,
NOAA National Marine Fisheries Service and Estuarine
Programs Office, and the US Fish and Wildlife Service.
This summary highlights the conclusions and recommendations
of the Stock Assessment Plan.
BACKGROUND
Stock assessment is the interpretation of fish population
data for describing the status of fish stocks and for
predicting the results of fishery management options. Stock
assessment analyses take population characteristics such as
growth, mortality, and reproduction and relate them to
controlling factors which include fishing pressure and
environmental distress such as climatic fluctuations,
pollution, and habitat degradation.
Maryland, Virginia, and the District of Columbia have all
been conducting stock assessments on selected species, but
many of the ongoing programs are limited in terms of
geographic coverage and range of species. The Plan
concludes that existing programs do not constitute a
comprehensive stock assessment program for the Bay and its
tributaries. In response, the Plan recommends the
cooperative development of routine, systematic assessments
in conjunction with cooperative, long-term data collection
programs for the Bay's fishery species.
vn
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WHAT DO WE KNOW ?
Chapter 2 of the Plan describes present knowledge of several
representative Chesapeake Bay finfish and shellfish species.
For some species, such as menhaden, there is adequate
information upon which to make informed management
decisions. Other species, such as the oyster, have not
received the level of attention their importance would seem
to warrant.
For the most part, the programs in the Plan have not been
described in a species specific manner, since it was felt
that this would be the most effective means of depicting the
needs of stock assessment. Specific requirements for
individual species will be reviewed in a document entitled,
Statusf Trends. Priorities, and Data Needs for Chesapeake
Bay Fisheries, to be produced during the summer of 1988.
DATA NEEDS
In general, there is sufficient basic biological information
for many species, but little reliable catch, effort, and
recruitment data is available. This deficiency is
significant because these data are the major types of
information required for stock assessment analyses.
Stock assessment data needs include improved catch data,
fishing effort data, and biological data (length, age,
weight, sex) from commercial and recreational fisheries.
These three categories are called "fishery dependent" data.
"Fishery independent" data are also necessary so that
unbiased information essential for stock assessments is
collected on juveniles and adults. Fishery independent
sampling does not rely on commercial or recreational
fishermen for collecting fish and is conducted through
standardized surveys, such as the Maryland beach seine
survey which is used to estimate a juvenile index for
striped bass.
Short-term intensive research is also needed to understand
the environmental and biological processes that affect
growth, mortality, and reproduction within fishery stocks.
The Plan calls for baseline fisheries data that are 1)
collected with standard methods Baywide, 2) precise and
accurate, 3) representative of the distribution and
abundance of Bay species, 4) inclusive of all major species
and their critical life stages, and 5) long-term in scope.
Vlll
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PROPOSED PROCESS FOR IMPLEMENTATION
Approximately 100 people are currently working on some
aspect of stock assessment in the Bay region at over twenty
organizations. Research, monitoring, and management
programs that contribute to stock assessment spend about
three million dollars per year; most of these funds ($2.5
million) are administered by federal agencies, in particular
NOAA and the Fish and Wildlife Service. Coordination of
personnel and financial resources will be a key goal for
implementing the proposed Baywide data collection program
and for conducting stock assessment analyses.
The Chesapeake Bay Stock Assessment Committee (CBSAC) was
formed in 1985 to improve the coordination of technical
stock assessment problems. The plan recommends that the
Committee continue its coordination role and begin to
oversee the active development of baywide stock assessments.
The major features of a Baywide stock assessment program and
recommended dates of implementation are summarized as
follows.
Fishery Dependent Programs: July 1989
Initiate a Baywide fishery statistics program to provide
improved estimates of catch and fishing effort for each type
of fishing gear and area of the Bay.
Outline procedures for collecting such data, to include the
implementation of a trip-ticket system for commercial
fishermen and more extensive recreational fisheries surveys.
Institute a program for obtaining species and age
composition, as well as other biological characteristics of
commercial and recreational catch.
Fishery Independent Programs: Spring 1989
Complete final design for a Baywide trawl survey to obtain
fishery independent estimates of abundance and distribution.
Augment trawl survey with other sampling methodologies to
obtain abundance indices for species and life stages not
captured by the trawl survey, such as the ongoing beach
seine surveys in Maryland and Virginia.
Develop research program to investigate the effects of the
environment on juvenile fish and shellfish populations.
Coordinate these surveys and studies with the Chesapeake Bay
Program Baywide Monitoring Program.
IX
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Stock Assessment implementation: July 1988
Chesapeake Bay Stock Assessment Committee (CBSAC) will have
oversight responsibilities for Baywide Stock Assessment.
Maintain CBSAC working group roles for reporting on status
of Bay stocks, investigating analytical techniques, and data
management.
Establish new stock assessment working groups on finfish,
oysters, and blue crab to begin immediately with the
evaluation of available data and proposed sampling programs.
Produce annual reports on the status of stocks, fishery
statistics, and periodic Baywide stock assessment reports.
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CHAPTER I. INTRODUCTION
BACKGROUND
Maryland and Virginia fisheries managers and scientists
began meeting informally in 1979 to discuss ways of
coordinating the collection of fisheries data information,
prior to even the "Chaffee Amendment" of P.L. 89-304.
Striped bass, shad and blue crab were targeted at that time
as the most important species. From these informal
meetings, a Planning Committee was appointed to formalize
future efforts. Consequently, shortcomings in catch
statistics, recruitment surveys, and data archiving were
discussed, and recommendations for achieving appropriate
Baywide statistical programs. A document, entitled Report
of a Workshop on Chesapeake Bay Fisheries Statistics was
generated, and the recommendations forwarded to the Bi-State
Working Committee, chaired jointly by the Natural Resource
Secretaries of the states of Maryland and Virginia, of the
Chesapeake Bay Commission. These recommendations were later
contained in a 1983 report entitled, Implementation of
Recommendations on Chesapeake Bay Fisheries Statistics, and
cited several needs and recommendations, relevant to the
current NOAA Chesapeake Bay Stock Assessment Program, and
included:
0 That Maryland and Virginia develop adequate,
quantitative, and coordinated fisheries data and
information systems.
° That Maryland and Virginia design and implement a
coordinated program of juvenile and adult monitoring
and biological sampling.
0 That Maryland and Virginia develop a compatible
automated data base management system for catch,
effort, and size distribution.
In 1983, the EPA Bay Report reiterated the importance of
stock assessment as a means of providing information on
living resources for water quality, as well as fisheries
management. The EPA Report, Governors' Conference, and Bi-
State Chesapeake Bay Commission recommendations made clear
the need for Baywide fisheries stock assessment. Action on
the part of the General Assemblies of Maryland and Virginia,
stemming in part from the 1982 workshop recommendations,
gave mandate to the regulatory and research agencies to
develop such programs. In 1984, action by the Congressional
delegations of Maryland, Virginia, and Pennsylvania resulted
in the inclusion of $1.5 million for Chesapeake Bay resource
assessments, oxygen depletion studies and fisheries
statistics in the FY85 NOAA appropriation law, P. L. 98-411.
As a result, NOAA generated its Chesapeake Bay Study Plan,
and at the same time coordinated the formation of the
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Chesapeake Bay Stock Assessment Committee (CBSAC). The
committee is composed of scientists and managers from
Maryland, Virginia, Pennsylvania, the District of Columbia,
and the Federal Government (NOAA NMFS, NOAA EPO, and FWS) .
The membership of the Committee reflects the recognition
that many of the Bay's fishery stocks cross jurisdictional
lines within and beyond the Bay, and that appropriate
assessment can only occur if the respective jurisdictions
work cooperatively.
The CBSAC Terms of Reference state that it will undertake a
program for the Baywide assessment of fishery resources
which will partition the effects of fishing mortality,
natural mortality, and contaminants on variation and trends
in abundance. Specifically,the Committee will:
0 identify and describe state and federal stock assessment
programs;
0 identify and describe additional data collection systems
needed to characterize the future status of the stocks
and explain their fluctuations;
° review fishery statistics needs and recommend programs to
improve the current fishery statistics collection
program;
0 plan and integrate biological effects studies with
stock assessments;
° recommend research projects; and
° provide guidance to Sea Grant to insure that low D.O. and
other biological effects studies on fish and shellfish
are supportive of stock assessment studies.
As of 1987, thirty research projects with total funding over
2.7 million dollars have been supported. The emphasis in
1985 and 1986 was on statistical interpretation of
historical data and on the evaluation of various stock
assessment sampling methods. The emphasis in 1987 was on
fishery independent sampling throughout the bay, utilizing
trawling.
The Stock Assessment Plan presents CBSAC's guidance for the
development of a Chesapeake Bay stock assessment program.
Many of the general recommendations of the Plan have been
presented in the past. Although positive steps have been
taken on past recommendations, progress has been slow
towards the development of cohesive inter- and intra-state
stock assessment programs. It is hoped that the completion
of the plan and the continuation of the Chesapeake Bay Stock
Assessment Committee will be the catalysts required to build
a cooperative program.
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The urgent need for baywide stock assessment is also
acknowledged in the 1987 Chesapeake Bay Agreement through a
commitment by the Bay's jurisdictions which reads:
"by July 1988, to develop, adopt, and begin to implement a
baywide plan for the assessment of commercially,
recreationally, and selected ecologically important
species."
This agreement commitment reaffirms the need to develop a
quantitative understanding of the relationships between
environment and fisheries in order to understand how to
appropriately rehabilitate the Bay.
GOALS AND OBJECTIVES FOR STOCK ASSESSMENT
Man's primary benefit from healthy fish, crab, clam, and
oyster stocks is the continued capability of harvest for
enjoyment, consumption, or profit. From this perspective,
it is the fisheries manager's goal to assure sustained
harvests. Likewise, one of the goals of environmental
management is to provide adequate habitat quality to support
living resources, which, in turn, would provide sustained
harvests. In fisheries management the optimum level of
sustainable harvest is determined through consideration of
biological and socio-economic factors. Three simply stated
objectives for meeting the goal of sustained harvest are (1)
quantify biologically appropriate levels of harvest, (2)
monitor current and future resource status for comparison to
harvest objectives, and (3) adjust resource status if
necessary and if possible through management. Stock
assessment is a process that will contribute to all three
management objectives.
In the Chesapeake Bay, the ability to accomplish any of the
three objectives for meeting the goal of sustained harvest
is limited by inadequate knowledge of the size of the
stocks, their variability, and the effects of fishing and
pollution on productivity and the recruitment of young fish.
A major constraint with regard to materially improving the
status of stocks is a lack of basic data usually available
for fisheries as valuable as those of Chesapeake Bay. To
rectify this problem it is necessary to define stock
assessment programs both within and among the states that
obtain required data and specifically address questions
which must be answered to achieve better fishery and habitat
management decisions.
WHAT IS STOCK ASSESSMENT ?
Fishery stock assessment refers to the process of compiling
and interpreting available and relevant information on the
fish stock in question. The objective of this process is to
produce an accurate statement detailing the status of the
stock (so far as the data allow) , to inform the decision-
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maker of options for management and to predict possible
consequences of resource management strategies.
Consideration is given to the population dynamics of the
stock, particularly growth, mortality, and recruitment
processes, and how fishing (or other anthropogenic
activities) affects any or all of these. Principal points
to note about stock assessments are the following: (1)
they are an attempt to describe the status of a fish stock
and the associated fishery; (2) they range from accurate
measures of the status of a stock to subjective estimates,
and (3) they require fishery, biological and sometimes
economic data, often long time series, to provide the
knowledge base necessary for fishery management decisions.
Using a liberal definition of stock assessment, Maryland,
Virginia and the District of Columbia have been conducting
stock assessments on a number of important species. Many
ongoing programs are limited in scope in terms of species
and geographic coverage and are primarily geared toward
collection of data rather than analysis. With these
shortcomings it can be argued that existing programs do not
constitute a comprehensive stock assessment program for the
Chesapeake Bay and its tributaries, neither in individual
jurisdictions nor in a Baywide context. A program suggests
routine, systematic assessments based on precise and timely
data. At the very least, these data must include catch and
effort from each component of fishing, and biological data
to include length-frequency (or age-frequency) and sex ratio
observations. For the most critical species, fishery
independent (scientific survey) information on abundance and
other stock parameters will be necessary.
A commitment to a long term, coordinated program for the
collection of these data is a necessary part of any stock
assessment program. While the objective of such a
commitment may be more closely aligned with the
implementation (or potential implementation) of management
regulations, the activity still constitutes biological
monitoring. Depending on the management issues and
biological events involved, information from an
environmental monitoring program may also be useful in stock
assessment; as such close coordination of the stock
assessment and monitoring programs in the Chesapeake Bay is
important. If anything the coordination will avoid
duplication of effort and inefficiency, and enable the
collection of data that would be better suited for analyses.
Close coordination will also enable the collection of a
broader range of information than would be possible by each
program individually. For these reasons this plan is
coordinated with the activities of the Chesapeake Bay
Program. Furthermore, the recommendations of this plan
concerning fishery independent and fishery dependent data
collection serve as the basis for the component of the
Chesapeake Bay Biological Monitoring Plan for bay finfish
and shellfish species.
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CHAPTER II. CHARACTERISTICS OF SELECTED BAY FISHERY SPECIES
Chesapeake Bay fishery resources may be categorized several
ways according to their life cycle, fishery, or management
protocol. Further, finfish and shellfish are separated in a
similar fashion. Of significance for management and
fisheries alike, is the fact that there are few finfish
fishery species that are year-round Bay inhabitants. Even
the Chesapeake Bay striped bass, after reaching sexual
maturity, is a seasonal visitor. Most commercial and
recreational finfisheries harvest seasonal transients that
migrate across coastal states' boundaries into varying
management regimes. Managing and assessing such transients
is far more complex than the management and assessment of a
year-round resident.
Some representative categorizations are as follows:
0 Anadromous spawners vs ocean spawners vs bay spawners
° Grazers vs apex predators
° Commercial vs recreational vs ecological importance
° Fishery (pound net, hook and line, hand tongs)
° Natural recruitment vs human-aided recruitment (hatchery
releases, seed transplants)
° Mobile (crabs) vs sessile (oysters)
Generally management and often assessments, are species
specific. The joint gubernatorial directive to develop
Baywide FMP's is on a species by species basis. This
approach to management is pragmatic and logistic and is
probably the best current system to use. Attention should
also be directed to the possibility of developing management
plans for multi-species fisheries by gear such as the pound
net. Further, the non-harvested stocks of ecological
importance such as the bay anchovy, silverside, killifish,
opossum shrimp (mysid), and grass shrimp should be
candidates for management. The Bay Program has focused,
since its inception, on the habitat; and while the fishery
managers need to concentrate their energy on control of the
harvest to effect management, they must not lose sight of
the importance of the habitat. Clearly in an estuarine
system resource management by habitat-resource
characterization is also a viable alternative.
The CBSAC stock assessment plan is a combination of fishery
dependent and independent assessment programs directed
toward providing data and information in support of
management. Non-species specific trawl surveys and
commercial/recreational catch sampling provide data for
assessment models and FMP's. While stock assessments are
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needed for these broad species groups, (e.g. the ocean vs
bay spawners, pound net catches, or commercial vs
recreational harvest), in the final analysis, questions are
directed to the status of stocks for individual species.
The 1983 EPA Bay Report described stock fluctuations in
anadromous and ocean spawners in an initial attempt to look
at cause and effect of the trends in these two "groups".
The concept of grouping these stocks ecologically according
to spawning areas is sound, and has a rationale that
supports management. Ocean spawned fish may prove harder to
manage than the Bay or river spawned species, as their
recruitment and harvest are more strongly influenced by
events outside of the Bay. Riverine species, on the other
hand, spawn where Bay state managers have the potential to
control both the environmental quality and harvest pressure.
Habitat requirements are a neglected categorization of
fishery resources. Recruitment processes described above
are different even though anadromous and ocean species are
taken in the same nets at the same time. Anadromous spawners
are influenced by river flow and rooted plant detritus forms
the basis for their food chain. Abundance of ocean
spawners, on the other hand, is influenced by offshore shelf
wind shifts and these spawners derive their energy from the
pelagic phytoplankton.
The Chesapeake Bay Program Living Resources Task Force
developed a habitat characterization report in 1987 that
identified our status of knowledge on resource habitats.
The identified gaps were many and should provide the
rationale for future research efforts on habitat-resource
requirements. A concurrent effort by the CBSAC Status of
Stocks Knowledge Work Group identified the types and
sufficiency of our knowledge about the biology and
population dynamics of the Bay species. The body of this
report is contained in a species matrix (Figure 1) and a
bibliography.
An examination of the matrix shows that for some species
(e.g. menhaden) there is adequate information upon which to
base informed management decisions. Other species such as
the oyster have not received the level of attention their
importance would seem to warrant. Further, the matrix shows
that for most other species we have sufficient basic
biological information, but that in the area of population
dynamics and catch/effort data little is available. This is
a significant omission as they are the parameters in the
various dynamic population models needed for the management
decisions. Indeed, it would appear that another way of
characterizing or categorizing species would be by our lack
of knowledge.
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ACCCPTACUE STATE OF KNOWLEDGE
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ANALYSIS UNDERWAY
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FIGURE 1. STATUS OF STOCK KNOWLEDGE
(CBSAC SOSK WORKING GROUP,
JAN 1988)
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An annual assessment of the status of the Bay stocks is an
objective of CBSAC. This will be contained in an annual
Status of Stocks (SOS) report patterned after the NEFC
Status of Stocks Report produced since 1976. The SOS report
will include both a biological status of the stocks, an
analysis of the fishery during the previous year, and a
report on the status of our knowledge. The status
descriptions for several important species that are
contained in the SOS report follow on the next several
pages.
AMERICAN SHAD, Alosa sapidissima
The American shad (Alosa sapidissima Wilson) is an
anadromous member of the herring family which ranges from
southern Labrador to northern Florida on the Atlantic coast.
Its spawning and nursery grounds are located in estuaries
and rivers. Shad rear in their river of birth for their
first summer, then migrate to the ocean, and eventually
return to their natal rivers to spawn about three years
later.
The American shad has been a popular and heavily fished
species valued for its flesh and roe for at least the past
two centuries in Atlantic coastal areas. Shad catches
peaked in Maryland in 1890, then declined until 1942. A
period of relative recovery in the 1950's followed,
especially in Maryland. However, by 1980 stocks in Maryland
were so low the fishery in Maryland was closed indefinitely,
with reported harvests having decreased from 184,221 pounds
in 1971 to 14,319 pounds in 1979. While such a catastrophic
reduction in catch (and presumably abundance) has not yet
occurred in Virginia, the trend in catch over the last ten
years has been downward. From NMFS surveys the recreational
landings were 61 and 65 percent by weight of the commercial
catch on the Atlantic coast in 1965 and 1970 respectively.
If the 1965 and 1970 surveys are approximately
representative, it is obvious that sportfishing for American
shad has been significant.
There are no reported results of standard production, yield-
per-recruit or stock-recruitment models for American shad
for the Chesapeake Bay. To be meaningful, these models
require data that currently does not exist for Chesapeake
Bay.
BLACK DRUM, Poqonias cromis
The black drum, Pogonias cromis (Linnaeus), ranges from Nova
Scotia south through the Gulf of Mexico to Argentina. It is
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most abundant along Texas, but is common along the Atlantic
coast from Chesapeake Bay to Florida. The black drum is the
largest member of the family Sciaenidae along the Atlantic
coast, attaining a maximum weight of 66.28 kg (146 Ibs).
Black drum enter coastal waters of Virginia during early to
mid-April, presumably migrating from offshore areas south of
Chesapeake Bay. Recreational fishermen begin to catch black
drum during early to mid-May in the lower portion of the Bay
and throughout the Bay as the season progresses. Adults
migrate southward and offshore by late fall.
Larval black drum utilize tidal currents to enter nursery
areas located in the mid to upper marsh areas throughout
Chesapeake Bay. Juvenile black drum have been reported to
enter Chesapeake Bay following the adults and disperse
throughout the Bay.
A question still exists as to whether black drum spawn in
Chesapeake Bay. A 1961 paper stated that spawning did not
take place in Chesapeake Bay because no larval black drum
were found. A later study identified black drum eggs
obtained from Chesapeake Bay near Cape Charles City, but
failed to delimit the area of spawning. They concluded that
spawning occurred along the seaside of Virginia's Eastern
Shore and the mouth of Chesapeake Bay. Ripe males and
partially spent females were observed in Virginia waters
during spring and early summer. This led to the conclusion
that spawning probably took place near the mouth of the
Chesapeake Bay. Spawning apparently occurs from early April
through mid-June, when water temperature is about 17.5°C
(63.5°F).
Black drum from the Gulf of Mexico reach maturity by the end
of their second year, at standard lengths (SL) of 285-330 mm
(11.2-13.0 in). Age at maturity of black drum is unknown
from along the Atlantic coast. Fecundity data for this
species is lacking as well; however, a 1929 study estimated
that a ripe female 1.1 m (43.3 in) in total length (TL) from
the Gulf of Mexico contained approximately 6,000,000 eggs.
Commercial landings of black drum in Virginia have averaged
approximately 30,000 pounds for the past fourteen years.
Prior 1972, landings for the Chesapeake Bay area ranged from
60-481,000 pounds.
The increased popularity of black drum as both a food and
game fish has brought this species to the attention of
various regulatory agencies. A minimum size limit for black
drum has been set by the VMRC at 16 inches TL. Commercial
harvesters and buyers are required to submit daily harvest
information to the VMRC, and anyone buying, or catching and
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selling black drum are required to obtain a Commercial
Harvest Permit.
BLUEFISH, (Pomatomus saltatrix)
The bluefish (Pomatomus saltatrix Linnaeus) is a migratory,
pelagic species which is distributed worldwide in the shelf
waters of temperate and warm-temperate latitudes. In the
western Atlantic it is found from Nova Scotia to the Gulf of
Mexico, and is particularly common in the Middle Atlantic
Bight especially from spring to fall. Bluefish are ravenous
carnivores that prey on a wide variety of invertebrates and
vertebrates throughout the water column.
Most bluefish mature by two years of age; males perhaps at a
smaller comparative weight. Sex ratios of spawning stocks
are approximately equal, as they appear to be at all other
life phases. Evidence suggests that two principal spawning
populations of bluefish exist along the Atlantic coast.
Spawning occurs over the "open shelf" and larvae develop in
surface waters. Major bluefish spawning sites in the
Chesapeake Bight are located offshore over the outer half of
the continental shelf, where water temperatures are 22° C
(72°F) or greater and salinities are 31 ppt or greater.
Initiation of spawning, as well as daily activity and
swimming speed are determined in part by temperature and
photoperiod. Year class success is postulated to be
dependent on the circulation of the continental shelf
waters; vertical or geographic position in the water column
determine when and where eggs and larvae are transported.
Bluefish exhibit complex migratory patterns which are not
well understood; apparently major differences between the
migratory routes of the two principal spawning stocks do
exist but further knowledge on migratory patterns is
limited. Reported commercial catch of bluefish along the
Atlantic coast dates to 1880. The peak reported commercial
catch for the Atlantic coast was about 21 million pounds in
1897 which was followed by a period of low harvests. A
trend of increased catches that began in 1960 was succeeded
by significant increases in the mid-1970's, but reported
harvests have since stabilized or declined slightly. From
1970-1982, reported Maryland commercial catches ranged from
1-6 percent of the reported Atlantic coast total of 4,715
tons (annual average); Virginia catches ranged from 10-40
percent.
Historically, the recreational catch of bluefish has been
many times larger than the commercial catch; since 1960, the
average distribution of removals along the whole Atlantic
coast is estimated to have been 12 percent commercial and 88
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percent recreational, based on reported commercial and
estimated recreational catch. From 1979-1982, the estimated
Chesapeake Bay recreational catch was 36 percent of the
estimated mid-Atlantic bight recreational catch, which was
in turn 52 percent of the estimated total Atlantic coast
recreational bluefish catch of 59,421 tons (annual average).
During the 1970's, a small quantity of bluefish was taken
annually by foreign fishing vessels (472,000 pounds
maximum). Currently, bluefish may not be retained by
foreign fishing boats. The Atlantic bluefish stock(s) seems
to have increased in abundance in the past ten years.
Evidence for an increase is based on the large increases in
both reported commercial and estimated recreational catch,
and on the results of Northeast Fisheries Center (NEFC)
surveys, in which abundance indices (number of fish per tow)
have generally increased during the same time period.
Since 1979, the MAFMC has been developing a bluefish
management plan for the Atlantic coast stock(s), and since
1985 the ASMFC has been working on one for their interstate
management. The plan allocates 20 percent of the total
projected bluefish catch for a given year to the commercial
fishery, 10 percent of which will be allocated to the New
England area, 50 percent to mid-Atlantic area, and 40
percent to the south Atlantic area.
BLUE CRAB, Callinectes sapidus
The blue crab is a common inhabitant of near-shore waters of
the Atlantic coast from New Jersey to Florida and along the
Gulf Coast. The Chesapeake Bay is the center of abundance
and produced 82.9 million pounds of hard crab, and 2.7
million pounds of peeler and soft crab with a total value of
$31.2 million in 1986. This compares with total average
annual Bay hard crab landings of 75 million pounds at $5.9
million from 1960 to 1970. Not only do these numbers
account for over half the total landings for the entire east
coast, but the Bay also provides almost all the United
States supply of soft crabs.
Blue crabs mate in brackish water, generally mid-spring
through summer, during which time they are called
"doublers". After mating, the females make their way down
the Bay to the higher salinity waters near the mouth of the
Bay where they overwinter. The males remain year-round in
the lower salinity waters further up estuary. During winter
when temperatures are below 8° C (47° F), blue crabs bury in
the mud or sandy bottom. It is at this time that the
females in the lower Bay are taken by the winter dredge
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fisheries. Females carrying eggs are called "sponge crabs",
and the eggs are extruded and hatch from mid-Spring through
summer. At first the larvae swim feebly in the near-surface
waters, but later descend to near-bottom waters. In the
surface waters they are susceptible to being swept out of
the Bay, but once in the bottom waters are transported up-
Bay in the estuarine circulation of the "salt wedge".
The blue crab may live three years, but most only survive
two years. Females mate when one year old during their
terminal molt, and after spawning they neither molt nor
grow. From May through September in their second summer
they are captured and sold as peelers. Late in their second
summer both males and females generally reach 5 inches
carapace width, the legal minimum size in Virginia. Sponge
crabs are protected when they enter the 130 square mile
"crab sanctuary" at the mouth of the Bay from 1 June - 15
September, but may be harvested outside the sanctuary.
Prior to the 1940's baited trotlines were the main fishery
in the Bay. Since then almost all hard crabs have been
taken in baited crab pots, with the exception of the winter
dredge fishery in Virginia that comprises some 15% of the
Bay catch. The recreational catch is undocumented but is
believed to be large. Peelers are captured by scrape,
"peeler pots", or a staked net called a "peeler pound".
Peelers are sold as bait for recreational fishing or held in
floating cages until they molt and become soft crabs.
Management of blue crabs, whether by state or bistate
regulation will be difficult, as the natural environment,
more so than the spawning adult population size, plays the
dominant role in establishing year class success.
Consequently, with the primary factors regulating stock size
not under the control of fisheries managers, effective
fisheries management may be difficult.
ATLANTIC CROAKER, Micropogonias undulatus
The Atlantic croaker is a medium-sized member of the
Sciaenidae family and ranges from Massachusetts to Mexico on
the North American coast and from Surinam to Argentina on
the South American coast. The species is most abundant,
however, along the southeast coast of the United States and
in the northern Gulf of Mexico. The Atlantic croaker is
iridescent overall, greenish silver above and silvery white
below. Numerous brassy or brownish spots form oblique wavy
lines on the upper sides and back.
Adult croaker tolerate a wide range of temperatures, 2-30° C
(35-86° F) and salinities (0-35 ppt), but the juveniles
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prefer the lower salinity and oligohaline environment of the
estuaries which serve as nursery grounds. Adult croaker,
like other sciaenids, spawn in the waters of the continental
shelf during the late summer and fall of their second year,
but return to the estuaries during the following spring.
Spawning occurs from August through December off the
Chesapeake Bay and south to Cape Hatteras.
Although estimates vary, reported size and age at maturity
suggests that Atlantic coast croaker are sexually mature
when 3-4 years old. The smallest reported mature male and
female were 24 cm (9.5 in) TL and 27.5 cm (11 in) TL,
respectively. Eggs and larvae drift toward land until they
are able to actively swim towards land and estuarine nursery
areas where they remain until the following fall.
Atlantic croaker are believed to reach a maximum age of 7-8
years when they are >500 mm (20 in) TL. The species feeds
on polychaetes, mollusks, mysids, decapods, other
invertebrates, and occasional small fish.
The croaker is one of the most freguently caught species in
estuarine and nearshore waters, particularly from March to
October. Maryland and Virginia have generally accounted for
the majority of the Atlantic coast croaker harvest. The
Virginia catch has varied from a high of 25,000 mt in 1945
to a low of 3 mt in 1968, peaking again in 1977 with a catch
of 3,900 mt before dropping once again. The 1986 harvest
totaled only 1,034 mt.
Maryland's landings show a similar trend, but the relative
catch was much smaller, the largest catch being 2,260 mt in
1944. The 1984 harvest totaled only 12 metric tons.
Maryland currently imposes a 10 inch minimum size for the
species. The Mid-Atlantic recreational catch, recorded
since 1979, declined between 1979-1980, but has since
steadily increased to 3,426 mt in 1984.
The abundance of Atlantic croaker seems to be closely
related to climatic trends and fishing pressure. Warmer
temperatures appear to favor the species as evidenced by
increases in landings during the first part of the 20th
century. Between 1958 and 1971, increased fishing pressure
and cold winters reduced the Atlantic catch to <3,000 mt
from 1961-1973. Subsequent increases and decreases in catch
after 1973 seem to be correlated with fluctuations in the
fishing effort and general temperature trends during that
period.
AMERICAN EEL, Anauilla rostrata
The American eel, Anquilla rostrata (Lesueur) is a
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diadromous species found in coastal waters from Greenland
and Northern Canada to the Gulf of Mexico and the West
Indies. The species is also widely distributed in inland
waters, including the Great Lakes, the Mississippi drainage
as far as South Dakota and west to the Rocky Mountains.
American eels are believed to spawn between Bermuda and the
West Indies, in the vicinity of the Sargasso Sea. Spawning
occurs from February through June. The larval stage eel is
called a leptocephalus. During the leptocephalus stage,
which lasts one or two years, currents distribute the larvae
in an apparently random manner along the Western Atlantic
Coast. Transformation from the leptocephalus to the glass
eel stage is complete by the time eels reach the coast.
After arriving in coastal regions they gain pigmentation and
are then called elvers. Within a few months elvers enter
the yellow eel stage which lasts until sexual maturity is
reached 5 to possibly 18 years later.
At the present time, eels are not a desirable recreational
species, but commercial fisheries are carried out for both
elver and yellow eel stages. In many areas, elvers are
trapped and used for stocking lakes and reservoirs. Yellow
eels are widely used as bait in the blue crab trotline
fishery in Chesapeake Bay, and in recent years a live eel
export fishery has developed. Although the American eel is
an important commercial species, catch statistics are
probably not a reasonable indicator of actual harvest levels
because of a lack of reporting requirements and because of
the nature of the fishery itself. For example, statistics
for the elver fishery are not available, and only crude
estimates of the yellow eel harvest used as bait in the blue
crab fishery exist.
ATLANTIC MENHADEN, Brevoortia tvrannus
Atlantic menhaden, or bunker, is a member of the Clupeidae,
or herring family. Although very similar to the alewife and
shad in appearance, menhaden are distinguished by a mouth
lacking teeth, and a dorsal fin located between the anal and
pelvic fins. The body is bluish above and the sides are
silvery with a reddish tint. A dark spot followed by
several smaller spots is present on the shoulder.
Atlantic menhaden are a euryhaline species inhabiting bays,
sounds and estuaries from Nova Scotia, Canada to West Palm
Beach, Florida. The species travels in dense schools of 50-
200,000 fish and makes extensive north-south coastal
migrations. In the spring, menhaden travel north with
larger, older individuals moving further north than the
younger, smaller fish. During the autumn, Atlantic menhaden
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migrate southward where they are usually intercepted by
fishing fleets off North Carolina.
Spawning occurs in different locations throughout the year.
Menhaden become sexually mature usually between age 1 (8
inches) and age 2 (10 inches) with all capable of spawning
by the third year. Fecundity estimates range from 38 to 631
thousand eggs for each female. The eggs float freely and
hatch at sea, and wind and currents carry the larvae into
sounds and estuaries where the young spend their first year.
Phytoplankton and zooplankton serve as the major food
source. Menhaden are an important forage for mackerels,
Atlantic bonito, bluefish, striped bass, and weakfish.
Although not a desirable recreational catch, menhaden have
been caught by commercial fishermen since the mid-1800's,
and reports of their importance to the earliest colonists
are freguent. The stock is concentrated in different areas
along the Atlantic coast at different times of the year, and
the fishing fleets follow them as they move.
Menhaden are caught by pound nets and gill nets year-round
in the Chesapeake Bay. The use of purse seines is
restricted. No purse seines are allowed in Maryland; while
Virginia allows them, but only between the third Monday in
May and the third Friday in November. Each year commercial
fishermen land more Atlantic menhaden than any other fish in
the United States. Since 1969, landings in the Chesapeake
Bay - Mid-Atlantic region have varied from 150,000 metric
tons (mt) in 1975 to 283,000 mt in 1980 when purse seine
landings in this region represented 70% of the total
Atlantic menhaden harvest. Since 1980, the Chesapeake Bay -
Mid-Atlantic catch has averaged 240,000 mt.
Stock assessments in the Bay are conducted by NMFS-Beaufort.
AMERICAN OYSTER, Crassostrea vircfinica
The American or eastern oyster, Crassostrea virqinica.
builds intertidal reefs in higher salinity waters along the
entire east coast of North America from the Gulf of St.
Lawrence to the Yucatan and West Indies. In estuarine
locations, where lower salinity water provides some refuge
from predation, deeper subtidal reefs or "rocks" are common.
Such oyster rocks are present throughout the shallow
portions of the Chesapeake Bay and its subestuaries. The
genus Crassostrea is notable for its tolerance to wide
ranges of salinity, temperature, turbidity and oxygen
tension.
Oysters are characterized by lateral compression of the body
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and the division of the shell into two halves (valves -
hence the term bivalve) separated by a non-calcareous
ligament. The valves are unequal and have no hinge teeth
(except in the larval stage). The typically bivalve foot,
byssus, and anterior adductor muscle are either much reduced
or missing. Only the posterior adductor muscle remains in
the sessile, attached adult form.
The genus Crassostrea is characterized by variably shaped
(ecomorphic) shells. The adult usually rests in the left
(cupped) valve; however, in dense reefs, oysters often
orient vertically with both valves pointed upward.
Internally, the mantle extends to the margins of the shell.
Ecological and physiological data suggest the presence of
several physiological "races" of Crassostrea virginica along
the eastern coastline of North America. Such "races" have,
however, been actively mixed through fishery-related
transplanting for at least a century especially so in the
Chesapeake Bay. In experimental culture, C. virginica has
been shown to hybridize with C. rhizophorae. the mangrove
oyster, and C. qigas. the Pacific oyster.
The oyster is dioecious (separate sexes) but also exhibits
protandry and protogyny (ability to change sex, male to
female and female to male, respectively). Oysters can
mature sexually at 2 to 3 months of age, usually in response
to increased temperature and availability of food. Spawning
is stimulated above a temperature which characterizes the
aforementioned "race"of origin. This temperature may vary
from 17 to 25° C (63-77° F) and increase progressively for
more southerly "races."
Fertilization is external. The planktonic larvae are
typically bivalve, filter feed predominantly on
phytoplankton, and remain in the water column for 2-3 weeks
depending upon salinity, temperature and food conditions.
Larval behavior is complex and suspected to play an
important role in retention in estuarine and coastal waters
and selection of substrate for settlement and metamorphosis.
Larvae exhibit gregarious settlement and specificity to hard
substrate. These behavioral traits are central to the
maintenance of oyster reefs or "rocks" as distinct
biological and geological features.
Adult filter feeding activity is influenced by temperature,
salinity and sediment load. A large oyster can filter
several liters of water per hour. Consequently, oyster
reefs or "rocks" are major components of sedimentary
processes in estuarine and coastal systems.
Historically, the oyster reefs of the Chesapeake were much
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more extensive than present day. Inadequately controlled
exploitation followed by decimation and essential
elimination of significant Chesapeake Bay oyster stocks in
higher (> 20 ppt) salinity seawater by MSX (a
haplosporidium, Minchinia nelsoni) after 1960 has left a
resource that is only a fraction of its original size.
Continued intense disease and fishing pressure present
little hope for expansion of the resource in the near
future.
The market oyster season in Virginia and Maryland runs from
1 October through 31 March. A market oyster in Virginia and
Maryland is 3" long.
Both Maryland and Virginia have extensive monitoring and
research programs directed at understanding oyster biology.
In spite of these efforts, little is known about the
population dynamics of the stocks as they relate to
management. While oyster biology shows a degree of
similarity Baywide, there are many differences even between
river systems. To be effective, management will have to be
on a river-by-river basis.
ALEWIFE, Alosa pseudoharengus
BLUEBACK HERRING, A. aestivalis
The alewife, Alosa pseudoharengus. and the blueback herring,
A. aestivalis. are anadromous members of the family
Clupeidae, and collectively are referred to as alewife or
gaspereau in Canada and as river herring in the United
States. In both countries the commercial landings are
reported as alewife. Collective reference to the two
species stems from similarities in their appearance, times
of spawning, methods of capture, and the juxtaposition of
spawning grounds. The commercial catches are used primarily
for bait, pet food, fish meal, and in Canada, a substantial
portion of the catch is salted and exported for human
consumption. Small, local markets exist for smoked river
herring and fresh or canned roe.
The alewife and the blueback herring have a largely
sympatric distribution. Alewives occur from Labrador and
Newfoundland to South Carolina, while blueback herring range
from Nova Scotia and northeastern New Brunswick to Florida.
Adults are generally distinguished at capture on the basis
of eye diameter, body depth, and peritoneum color. The
diameter of the alewife eye is larger than the distance
between the tip of the snout to the forward edge of the eye,
but the two measurements are about egual in blueback
herring. The alewife body tends to be deeper, and its
peritoneum is pale (pearl-grey to pinkish white), sometimes
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with dusky spots (melanophores); in contrast, the blueback
herring peritoneum is black but sometimes soot-grey with
darker spots.
The onset of river herring spawning is related to water
temperature; thus, it varies with latitude, and it may vary
annually by 3 to 4 weeks in a given locality. There is
considerable overlap in the spawning seasons of the two
species. Spawning for alewife generally begins between 5 to
10° C and for blueback herring, between 10 to 15° C.
Alewives begin to spawn 3 to 4 weeks earlier than blueback
herring, but their peaks of spawning differ by only 2 to 3
weeks. In the Chesapeake Bay region the onset of spawning
is about mid-March in Virginia streams and the last of March
in Maryland streams. Both species return to sea shortly
after spawning.
When spawned in flowing streams, river herring eggs (after
the loss of adhesiveness) and larvae are transported
downstream. In Chesapeake bay tributaries, juveniles
(young-of-the-year) are distributed widely throughout tidal
freshwater nursery areas in spring and early summer, but
subsequently move upstream in summer with the encroachment
of saline water. With decreasing water temperatures in the
fall or early winter, the juveniles move downstream as a
first stage of their seaward migration. Some juvenile Alosa
will remain in deep estuarine waters through the winter.
First spawning by river herring occurs from ages 3 to 6,
with the composition of virgin spawners strongly dominated
by age 4 fish. In general, spawning stocks of river herring
are comprised of ages 3 to 8. Males tend to dominate age
classes 3 to 5, while females live longer and, thus,
dominate the older age classes.
The male to female ratio throughout a season tends to favor
males, about 2:1. Male domination of the sex ratio is
probably due to a greater proportion of males maturing at
ages 3 and 4. Males tend to dominate in the early runs, but
the proportion of females increases (sometimes
significantly) in the later runs.
There is considerable variation in the mean lengths at age
reported for river herring. Part of the variation is
undoubtedly natural, but part is due to different methods of
back calculating lengths at age. In general, females of
both species are larger than males, and alewives are
somewhat larger than blueback herring. Most reported
maximum total lengths range from 12.1-13.7 in (310 to 350
mm) .
Very positive contributions to freshwater ecosystems can
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result from the presence of river herring. All life stages
of both anadromous and landlocked river herring are
important forage for many freshwater and marine fishes and,
in addition, birds, amphibians, reptiles and mammals have
also been documented as predators. Due to mortality on the
spawning grounds, anadromous alewives were shown to be a
nutrient source to a system rather than just a mechanism for
nutrient regeneration.
RED DRUM, Sciaenops ocellatus
The red drum, Sciaenops ocellatus, is one of the 22 members
of the drum family known for the drumming or croaking sounds
produced by vibrating their swim bladders. The species is
also known as channel bass, puppy drum (juveniles), spottail
bass, and redfish. They are silvery-gray overall with a
coppery cast. One or more black spots are present at the
base of the caudal fin. The species is also recognized for
the subterminal mouth and the lack of barbels on the chin.
Red drum range from Massachusetts to Key West, Florida, on
the Atlantic coast but are not common north of New Jersey.
They also inhabit the Gulf of Mexico from the southwest tip
of Florida to Vera Cruz, Mexico.
Spawning takes place in nearshore ocean waters near passes
and inlets. On the Atlantic coast spawning may begin as
early as July and continue through December, or possibly as
late as mid-February, peaking in late September or October.
Sexually mature males are 18-20 in. (age 1+, 470-530mm FL) .
Females mature at ages II and III or 23-30 inches FL (575-
760mm FL) .
Problems with age determination techniques have prevented
documentation of the maximum age for red drum. An estimate
based on banding patterns on otoliths, however, suggested a
maximum age of 33 years.
Crabs, shrimp, fish such as striped mullet, spot, pinfish,
and pigfish compose the majority of the diet of adult red
drum. Smaller individuals less than 3 in (75 mm) SL feed
mainly on small bottom invertebrates and other juvenile
fish.
Maryland-Virginia red drum are commercially harvested in
estuaries and ocean water in a mixed species fishery by
several gear types. These include haul seines, fish trawls,
pound nets, gill nets, hand lines and trammel nets. Pound
nets and fish trawls have claimed the majority of red drum
caught in Virginia since 1977. Most of the fish are landed
between May and October in Virginia and year-round from
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North Carolina to Florida. The recreational fishing season
in the Chesapeake Bay lasts from late April to November. In
Virginia, recreational landings exceed the commercial.
Current regulations in this state prohibit the possession of
more than two red drum greater than 32 inches total length
or any less than 14 inches TL.
Data on commercial landings of red drum have been collected
since 1880 with Atlantic coast landings being consistently
lower than those of the Gulf of Mexico. Red drum landings
reached 83 mt in 1950. With the exception of 2 years, 1965
and 1983, Virginia landings have not exceeded 9 mt over the
past 20 years.
SPOT, Leiostomus xanthurus
The spot is a member of the Sciaenidae, or drum family,
which inhabits estuaries and coastal waters from
Massachusetts to Mexico. They are distinguished from other
sciaenids by the lack of chin barbels and by their silvery-
gray body and 12-15 dark lines extending from the dorsal fin
to the lateral line. A prominent black spot about the size
of the eye is located behind the gill cover.
During the summer, spot are found in shallower waters from
Delaware to Georgia. Later in the year they tend to move
offshore onto the shelf edge from Cape Hatteras to central
Florida where they remain throughout the winter. Spot
generally tolerate a wide range of salinities (fresh to 37
ppt) and temperatures 2-35 C (35-95 F) ; however, long cold
spells are known to cause extensive mortalities.
Spot spawn at sea in the fall and winter when water
temperatures are between 59-79 F, although the spawning
season is extended from September through November off the
Chesapeake Bay. Most individuals on the Atlantic coast are
sexually mature by the end of their second year or the
beginning of the third year when they are 186-214 mm (7.0-
8.5 in) TL. Data on fecundity are scarce, but fecundity
estimates for spot 158-187 mm (6.0-7.5 in) SL range from
77,730-83,900. The estuaries serve as nursery grounds for
the larvae. As they mature, the juveniles move up into less
saline or fresh water where they remain throughout their
first winter.
Spot grow rapidly during the first year attaining a length
of 132 mm. Their reported maximum age is IV in the
Chesapeake Bay and V near North Carolina. They feed on a
variety of foods such as crustaceans, polychaetes, detritus,
and small fish.
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The spot is a popular catch for both recreational and
commercial fishermen. A migratory species which travels in
large schools, the spot is especially accessible to pound
net harvest by commercial fishermen. Landing statistics
since 1930 reflect great fluctuations in the harvest. In
1952, landings of spot reached a high of 14.5 million Ibs.
but have since varied between 3.9 million and 12.7 million
Ibs. The greatest proportion of the commercial catch comes
from the Chesapeake Bay and South Atlantic regions, although
since 1960 the South Atlantic states have dominated the
fishery.
In 1949, the Chesapeake landings reached 8.7 million Ibs.,
fell sharply in the 1960's, and peaked at 6.4 million Ibs.
in 1970. Maryland and Virginia landings in 1985 totaled
44,000 Ibs. and 737,000 Ibs., respectively. The estimated
recreational catch along the entire Atlantic coast ranged
from 13.3 million Ibs. in 1980 to 4.1 million Ibs. in 1984.
Spot are one of the species that can be adequately sampled
by a trawl survey.
There is no minimum size limit for spot in Virginia or
Maryland.
STRIPED BASS, Morone saxatilis
The striped bass (Morone saxatilis Walbaum) or rockfish as
it is commonly called in the Chesapeake Bay region is an
anadromous species which ranges from the St. Lawrence River,
Canada to the St. John's River, Florida on the Atlantic
coast. Striped bass spawning in Chesapeake Bay occurs from
April to June at (or near) the surface in fresh or slightly
brackish water. Peak spawning activity is observed between
15° C and 20° C; however, salinity, turbidity, and
temperature, as well as other factors affect egg and larval
survival. Rockfish assemble in small groups before age two
and thereafter generally travel in schools.
Little migration out of the bay occurs in striped bass
before 3 years of age. Tagging studies and age composition
data from the coastal fisheries indicate that most female
striped bass migrate out of the Chesapeake Bay at about age
3; conversely, in Maryland, relatively few males ever
migrate out of the region. The coastal migratory stock,
believed to be typically dominated by rockfish of Chesapeake
Bay origin, apparently moves along the Atlantic coast from
New England to North Carolina. Movement is generally
seasonal: north in spring, south in autumn.
The coastal migratory stock of striped bass has been
characterized by the periodic entrance of a dominant year
21
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class into the fishery. The last such year class in
Chesapeake Bay occurred in 1970 and resulted in peak
commercial landings in the coastal states in 1973. The
reported commercial and recreational catch data, CPUE and
the Maryland juvenile index all indicate that striped bass
abundance in the Chesapeake Bay has suffered a continuous
decline since 1973. The decline in landings since 1973 is
probably attributed to a combination of three primary
factors: (1) natural fluctuations, (2) overfishing, and (3)
degraded water quality, including pollution and loss of
spawning habitat. Maryland juvenile index data indicates
that mortality in the fishable stock may have increased
since the early 1970's, which may explain the observed shift
in landings from 4 and 5 year olds to 2 and 3 year olds.
A coastwide management plan for striped bass was adopted by
the Atlantic States Marine Fisheries Commission (ASMFC) in
1982. The ASMFC suggested that states enforce a 14 inch
total length minimum size limit on striped bass in inland
waters, and a 24 inch total length minimum size limit on the
coastal fisheries. The plan further urged that major
spawning areas or rivers be closed during the spawning
season.
By 1987 the amendments to the plan called for a 95%
reduction in mortality of 1982 year class females and
subsequent year classes until such time as 95% of the
females spawned. This resulted in a 24" Bay/31" ocean size
limit in Virginia, and a 6 month closure to fishing (June -
November). In 1984, based largely on the relentless decline
in catch, reduced abundance of spawning females, and eleven
years of below average reproduction, Maryland initiated a
striped bass moratorium effective the beginning of 1985.
Currently, there are several positive signs of stock
recovery. In Maryland, the number of 4 year old female
spawners (1982 year class) sampled on the spawning grounds
in 1986 was greater than any year since sampling began in
1982. However, indices of egg deposition exhibited only a
slight upward trend in 1986, and the number of older females
was found to be decreasing. A larger percentage of the 1982
year class will be mature in the spring of 1988 and will be
joined by spawners of other year classes which have been
protected.
The Maryland juvenile striped bass index of 4.8 improved
slightly in 1987, but was still less than the long term
historic average of 8.8 (the Interstate Fisheries Management
Plan established a 3 year running average of 8.0 as one of
the criteria that signals reproductive recovery). According
to the Maryland Striped Bass Annual Report, a continuation
of the Maryland striped bass moratorium will afford the
current female spawning stock, and those that will
22
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eventually become mature, the protection from fishing
mortality which they require. In Virginia the juvenile
index continued to show an upward trend since reaching a low
in 1980.
Adult striped bass are assessed when on the spawning rounds
in Maryland using gillnets, and in Virginia from poundnet
catches. Juvenile abundance is estimated each summer during
directed young-of-the-year seine surveys in each state.
SUMMER FLOUNDER, Paralichthvs dentatus
The summer flounder is a commercially important flatfish
species that generally ranges from Cape Cod to northern
Florida, with occasional capture north of Cape Cod. During
the late spring to early fall, adults are found in coastal
and estuarine waters, to as shallow as 1 m. Decreasing
water temperatures and changes in photoperiod cue the annual
fall migration of fish north of Chesapeake Bay to offshore
spawning and wintering grounds on the middle and outer
portions of the continental shelf respectively. Fish south
of Chesapeake Bay spawn and overwinter on the inner/middle
continental shelf.
Reproductive data from specimens collected on 1974-1979 NMFS
bottom trawl surveys between Cape Cod and Cape Lookout
indicate that most spawning occurs between October and
February. Fish north of Chesapeake Bay spawn from September
to December, whereas fish south of Chesapeake Bay spawn from
November to February.
Eggs rise to the surface and are presumably transported by
wind driven surface currents. Winds from the NW to NE are
believed to cause the successful transport of larvae to
estuarine nursery habitats. It has been suggested that the
major nursery areas are in Virginia and North Carolina.
Juveniles seem to prefer mesohaline/polyhaline nursery
areas, where maximum growth rates occur. Juvenile summer
flounder remain in estuarine and coastal waters until ages
2-3.
Summer flounder are fully recruited to the commercial
fishery at ages 2-3. The optimal age at entry to the
fishery is 5-7 years for females and 4-5 years for males.
Commercial landings in Virginia increased significantly in
1973 and have remained at a relatively constant level since
then. The increase in landings may have been due to
increases in fishing effort and fishing power in the
offshore trawl fishery. Commercial landings in Maryland
also increased in 1973 and remained at a higher level
23
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through 1979. Landings decreased substantially between 1981
and 1986. Recreational catch data, though not as extensive
as commercial catch data, indicates that 45-70% of total
U.S. summer flounder landings can be attributed to the
recreational fishery. The recreational fishery has the
potential to significantly impact the commercial fishery
(coastal and offshore) because it catches younger fish prior
to their recruitment to the commercial fishery. The minimum
size limit in Virginia and Maryland is 12 in (30.5 cm).
Young flounder are first sampled in trawl surveys during
their second year. Young-of-the-year which inhabit shallow
vegetated areas are not susceptible to trawling gear.
WEAKFISH, Cynoscion reqalis
The weakfish, Cynoscion reqalis. also known as the gray
trout or squeteague, is a member of the drum family,
Sciaenidae, so named for the drumming sounds created by
vibrating the swim bladder. The body is elongate and
moderately compressed, olive above and silvery on the sides
and underside. Dark blotches mark the upper body in oblique
wavy lines. The dorsal and caudal fins are dusky, while the
ventral, anal, and margin of the caudal fin are bright
yellow. Two large recurved teeth are present in the upper
jaw.
Weakfish are found in coastal waters from southern Florida
to Cape Cod, Massachusetts, but are most abundant from New
York to North Carolina. With rising water temperatures
during the spring, weakfish migrate northerly and inshore
into bays, sounds, and estuaries. During the fall and
winter, the younger weakfish less than 4 years old move
offshore and south, often as far south as Florida, while
older fish move further offshore and only as far south as
North Carolina.
Spawning, hatching, and larval development occur in
nearshore and estuarine waters between March and October
with peak production between late April and June. The mouth
of the Chesapeake Bay is the major Virginia-Maryland
spawning ground. Weakfish grow rapidly and are reported to
reach a maximum age of 11 years old (approximately 11.6
pounds). Males reach sexual maturity when approximately 1
year old or 5-6 inches (130-150mm) SL, while females are
slightly larger (145-190mm SL or 5.7-7.4 in) before
attaining sexual maturity. The species is also highly
fecund: a female 500mm (19.7 in) TL may produce over two
million eggs at one time. Young gray trout feed primarily
above the bottom on mysid shrimp and anchovies, while older
individuals feed throughout the water column mostly on
24
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herrings, anchovies, silversides, other fish, and blue
crabs.
Weakfish are a valuable commercial and recreational sport
fish found along the United States east coast. Commercial
catch statistics indicate that weakfish landings have
fluctuated widely, increasing from a recent low of 1,397 mt
in 1967 to 16,293 mt in 1980. Recreational landings also
peaked in 1980 at 21,064 mt. In Virginia the commercial
catch dropped from 6.2 million pounds in 1980 to 2.0 million
pounds in 1986. The Maryland landings suffered a similar
decline from 568,000 pounds in 1980 to 173,000 pounds in
1986.
Results of a weakfish stock assessment indicate that
weakfish from Maryland to North Carolina may have
experienced both growth and recruitment overfishing in
recent years: however, these conclusions are uncertain due
to weaknesses in the data set used in the analyses and lack
of knowledge of weakfish stock structure.
WHITE PERCH, Morone americana
The white perch (Morone americana Gmelin) is a semi-
anadromous schooling species found primarily in shallow,
brackish waters, and ranging from Nova Scotia to South
Carolina. It is most abundant from the Hudson River to the
Chesapeake Bay. This species is both adaptable and broadly
tolerant and hence is capable of dominating fish communities
in both fresh and estuarine waters.
White perch migrate upriver to areas of low salinity for
spawning after overwintering in deep, saline waters.
Spawning occurs from late March through June, and has been
found to peak at temperatures around 10 C in Chesapeake Bay.
Following spawning, adults move downstream to brackish
waters in the middle and lower estuary. Within the
Chesapeake Bay, young white perch move progressively
downriver as they develop from egg through juvenile stages.
Evidence suggests that environmental factors including
temperature, fresh water flow, dissolved oxygen,
competition, and predation are related to survival of white
perch larvae and early juveniles and subsequent
establishment of year-class strength. The young grow
rapidly during their first year, often reaching 40% or more
of their maximum size. This rapid growth of white perch
combined with production of large numbers of offspring and a
wide environmental tolerance range has allowed the species
to rapidly colonize new environments.
Historically, the white perch has been an important food
25
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fish in the Chesapeake Bay region. Annual landings are
perpetually variable apparently due largely to climatic
conditions.
YELLOW PERCH, Perca flavescens
The yellow perch, Perca flavescens. inhabit cool water lakes
and reservoirs, coastal rivers, streams and low salinity
estuaries from Canada to South Carolina. They have 6 or
seven vertical black bands extending across the back and
yellow to bright red pelvic and anal fins.
Males are sexually mature at 2 years of age, or about 5 in
(12.7 mm) long, and females at 3 years or 6 in (15.2 mm).
Spawning occurs in shallow water between March and April.
A female may release from 3 thousand to 150 thousand eggs at
a time. The eggs are deposited in a gelatinous strand which
is left among vegetation and submerged branches.
Yellow perch may live up to 13 years and attain a weight of
4 pounds, but most are small and only 5-8 in (13-20 cm)
long. Their diet is largely composed of benthic insect
larvae, leeches, amphipods, crayfish, and small fish.
The yellow perch is a valuable sport and commercial species
which is primarily encountered on its spring spawning run.
The commercial fishery is centered in the upper Maryland Bay
and freshwater reaches of the main-Bay tributaries.
Commercial landings have undergone a dramatic decline since
the 1880's when Maryland landings were estimated at over 1
million pounds. In 1985 Maryland landings had dropped to
only 43,000 pounds. There are no minimum or maximum size
limits in Maryland or Virginia at this time.
BAY ANCHOVY, Anchoa mitchilli
The bay anchovy (Anchoa mitchilli Valenciennes) is a widely
distributed engraulid, found in coastal, estuarine and
freshwater habitats along the Atlantic seaboard from Cape
Cod to Yucatan, Mexico. Bay anchovy is one of the most
abundant fish species in its range and probably is the
single most abundant fish in Chesapeake Bay. It is a small
species with a maximum size not exceeding 110 mm (4.33 in),
and individuals larger than 90mm (3.54 in) are uncommon.
There is no commercial or recreational fishery for bay
anchovy. Its small size and habit of aggregating in small
schools make it an unlikely target for future fisheries.
However, bay anchovy is an important forage species for
predator fishes throughout its range. Predators include
26
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striped bass, bluefish, weakfish and summer flounder. Bay
anchovy primarily feed on zooplankton and thus are an
important link between primary producers and harvested
predator species in many ecosystems, including the
Chesapeake Bay.
Male and female bay anchovy mature at age 0+ when 35-4Omm
(1.4-1.6 in) in length. Spawning season varies with
latitude, being more protracted in the southern part of its
range. Most spawning in the Chesapeake region occurs from
mid-May through mid-September. Spawning occurs over a wide
range of salinities and temperatures (15-30 C) . Eggs and
larvae are abundant in both shelf and estuarine waters.
They are the most common component of the Chesapeake Bay
ichthyoplankton in summer months. Larvae hatched in May
probably mature and spawn by mid-August, based on reported
larval growth rates. Larvae that occur in Chesapeake Bay
tributaries tend to be transported upriver. Entrainment and
impingement of young bay anchovy in power plant intakes is a
problem in the Chesapeake and other estuaries.
Causes for interannual variability in abundance and
recruitment are little known, primarily because bay anchovy
is not exploited. Long-term trawling surveys in the
Virginia part of the Chesapeake Bay and egg and larvae
abundances indices in Maryland have suggested major
fluctuations in yearly abundance. Unlike more northern
estuaries where bay anchovy migrate offshore in winter and
have variable return rates the following spring, Chesapeake
Bay populations overwinter in the Bay. Abundance of mature
individuals in the Chesapeake region apparently is highest
in late summer (August-September) when new recruits
predominate.
The population dynamics are relatively little understood.
Bay anchovy is short-lived; length-frequency and otolith
(ear bone) analyses indicate that maximum age probably does
not exceed 3+ years. Few individuals attain two years of
age. Adult mortality rates seldom have been estimated. In
the Delaware Bay during 1983, annual mortality was estimated
to average 80.2%, based on mean daily rates. Fishery
assessment models have not ,been applied because the species
is not exploited. Considerable literature, both in
published form and reports, is available on the dynamics of
bay anchovy populations exposed to power plant entrainment
and impingement effects.
KILLIFISHES, Fundulus sp.
The killifishes, principally the common killifish, F.
heteroclitus, and the striped killifish, F. maialis. are
27
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common marsh and tidal creek nearshore species in the Bay
and its tributaries. They inhabit areas that are often
oxygen deficient in summer and exhibit large seasonal
temperature extremes. During winter they bury in the mud.
Spawning occurs during the spring on the spring tide. Eggs
are deposited above the normal high tide where they develop
and hatch the next month on the high spring tide. Killifish
are omnivorous and are one of the most common forage for the
blue, crested night, and green herons.
ATLANTIC SILVERSIDE, Menidia menidia
The Atlantic silverside, and its cousin, the Tidewater
silverside, M. berelina. are common species along the entire
Mid-Atlantic coast. The Atlantic silverside is common in
higher salinities, and the Tidewater silverside in lower
salinities; below 5 ppt only the Tidewater silverside is
taken. In the Chesapeake Bay these two species are
important forage for bluefish, striped bass and weakfish.
They support no commercial fishery but are one of the most
important ecological species in the Bay. The silverside
spawn in the spring, laying demersal eggs that are attached
to shoreline grasses. They grow rapidly reaching 60-80 mm
(2.5-3 in) by the end of the first summer, and after
spawning the following spring (April-May) reach 100 mm (4
in) before they die at 14-16 months of age.
In spite of their ecological importance they have not been
studied as extensively as many other Bay species.
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CHAPTER III. APPROACH TO STOCK ASSESSMENT
Chapter I describes general data needs for stock assessment;
Figure 1, a summary of present knowledge, accentuates the
many shortcomings in present data collection in the Bay and
tributaries. To, remedy these shortcomings, CBSAC has
devised a Baywide data collection program for fishery
assessment and management (Chapter IV) . In that program,
long-term monitoring programs are supplemented with shorter-
term surveys and special studies when needed to clarify
stock characteristics. Data collection and analysis provide
the basis for regular assessments of the status of each
fishery. The assessments, in turn, help define the data
that must be collected.
THE NEED FOR VALID LONG-TERM DATA
The most basic data needs of stock assessment (Figure 1)
include (1) knowledge of stock identity in a biological
sense; (2) estimates of growth and mortality rates; and (3)
catch and effort statistics by age and area. For valuable
species (especially short-lived species such as blue crab,
to which some stock assessment models are less applicable),
fishery independent indices of recruitment and spawning
stock size are also essential.
Necessary characteristics of data for management include:
(1) regularitv--timely. periodic, and continuous data
collection using standard equipment and procedures; (2)
precision and accuracy in sampling and recording; (3)
representativeness of the data, usually obtained through
control of sampling regimes; (4) inclusiveness of the range
of stocks throughout the Bay and tributaries, and (5)
temporal continuity, the collection of long series of
regular data over many years.
The pressing need for temporal continuity in the data arises
from the life histories of the resource organisms. Most
exploited species in Chesapeake Bay take two to ten years to
reach sexual maturity, and then produce only one new
generation each year. (Hence the expression "yearclass"
refers to a generation.) Lengthy life cycles mean that
detailed insight into population dynamics (of which an
important component is variation in yearclass strength) can
come only from analysis of data collected over years and
decades.
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PERSPECTIVES ON MANAGEMENT
Fishery assessment and management in Chesapeake Bay have
often been directed at single stocks; however, several
species (and therefore several stocks) are often taken in a
fishery, even when only one species is targeted. Assessment
of multistock fisheries generally begins, but should not
end, with a thorough understanding of each component stock.
Sufficient progress has been made in multistock assessment
techniques to make them useful in management. Use of these
approaches appears to be a logical step for contemporary
fishery management in Chesapeake Bay.
Ideally, fishery managers regulate fishing to obtain the
optimum sustainable benefit from the fishery. This optimum
necessarily considers both biological and socioeconomic
factors. However, the history of fishery management
includes numerous cases of stock collapses when
socioeconomic considerations were allowed to overrule sound
biological advice. The collapse of the California sardine,
the striped bass and American shad stocks of Chesapeake Bay,
the Georges Bank herring, the Pacific mackerel, and the
Atlantic salmon should speak clearly to us.
TYPICAL MODELS OF POPULATION DYNAMICS
In formulating scientific advice for management, fishery
scientists often employ mathematical models of fish stocks.
Although any model can only approximate the dynamics of a
living stock, the models described below contribute greatly
to our ability to understand population dynamics, formulate
objectives, and estimate the risks and benefits of
management strategies.
Surplus Production Models
The goal of surplus production models is to determine the
maximum sustainable yield (MSY) obtainable from a stock or
group of stocks. The model is based on a dome-shaped rela-
tionship between equilibrium yield (the amount of harvest
that can be balanced by growth and recruitment) and fishing
effort or stock size. The model's results are used to
regulate effort or harvest. In the example shown (Figure
2A) , fishing effort at point A results in equilibrium yield
(labeled "catch") of A'. To maximize yield, the fishing
effort is set at B, since any other effort level results in
lower equilibrium yield. Overfishing occurs at point C,
where increased effort results in lower yield. In an
unmanaged fishery, fishing effort tends toward excess; in
this example, effort in an unmanaged fishery might be at C,
and the quantity B' - C' would represent lost potential
yield.
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FIGURE 2. CONCEPTUAL RELATIONSHIPS BETWEEN (A) CATCH
AND EFFORT/ (B) EFFORT AND YIELD-PER-RECRUIT,
AND (C) STOCK AND RECRUITMENT (FROM ROTHSCHILD
ET AL, AN ACTION PROGRAM TO DEVELOP A MANAGE-
MENT SYSTEM FOR CHESAPEAKE BAY FISHERIES,
UMCEE8-CBL-84-7)
I
o
o
B'
C'
A'
ABC
FISHING EFFORT
CC
O
UJ
cc
I
t_
o
a
i
a
_i
UJ
J-
Z
UJ
ID
DC
O
UJ
a:
o
z
UJ
cc
B.
FISHING EFFORT
ADULT STOCK
31
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Problems with surplus production models include the
difficulty of knowing whether one is above or below MSY, the
need for long series of data (preferably over 10 years and
including years of sharply different population sizes), and
statistical difficulties due to variability in the data.
Surplus production models require, at the least, time series
of catch and effort data. In addition, time series of
abundance can be used to improve their reliability.
Although catch statistics are recorded for many species,
neither effort nor abundance is regularly measured for most
Bay species.
Dynamic Pool Models
Since recruitment fluctuates unpredictably from year to
year, a common management tactic is to maximize yield per
recruit; ie., to obtain the maximum yield in weight from any
level of recruitment. With knowledge of a stock's growth
and mortality characteristics, maximum yield per recruit can
be obtained by regulating fishing mortality and the minimum
age (or size) at capture. In Figure 2B, a minimum size of
14" gives the maximum yield per recruit; either a 12" or a
16" minimum reduces the yield. The optimal fishing effort
for a chosen minimum size is also obtained. Regulating a
fishery for maximum yield per recruit (or its variants) can
increase yield substantially, especially for relatively
long-lived species. However, since the model does not
control the level of recruitment, the stock can become
overexploited, even at optimum yield per recruit. The
solution to this dilemma is to employ the dynamic pool model
together with methods (or extensions of the basic method) to
monitor and control stock size. Another difficulty is that
the minimum size that provides optimum yield per recruit may
be unacceptable for socioeconomic reasons.
Dynamic pool models require timely estimates of growth and
mortality rates. These elementary data are not well known
for most species in the Bay (Figure 1).
Virtual Population Analysis
Virtual population analysis (VPA) allows the scientist to
retrospectively estimate recruitment and population size by
analyzing age-specific catch data from preceding years. VPA
can provide relatively accurate and precise estimates of
population size. These, in turn, can be used as input to
other models and to clarify the interpretation of such other
models. VPA requires a medium to long-term series of catch-
at-age data. Unfortunately, age-structured catch data have
been collected for only one or two species in the Bay
(Figure 1).
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Models of Stock and Recruitment
Although tremendous variability tends to obscure the
relationship, each year's recruitment is influenced by the
spawning stock size; i.e., the number of parents. A
simplified model of such a relationship is shown in Figure
2C. In management, it is crucial to conserve sufficient
spawning stock to ensure the stock's persistence; this is
best done through -knowledge of the stock-recruitment
relationship. Stock-recruitment models can also provide a
framework for evaluating the effects of external factors,
such as climate or habitat quality, on fish stocks. These
models require medium- to long-term sets of stock size and
recruitment estimates, which are not now available for most
Bay species.
Other Models
CBSAC has instituted several retrospective analyses of
Chesapeake Bay fishery data. Preliminary conclusions
indicate that statistical techniques such as Box-Jenkins
times series analysis and categorical regression may be
useful, especially as they can easily include environmental
factors that may affect stock dynamics. In addition,
fishery scientists are constantly refining and adding to
their collection of population dynamics models. However,
the usefulness all models depends on the type and quality of
data available.
CONCLUSIONS
It is clear from the above discussion that (1) fishery
scientists have developed a respectable repertoire of tools
(models) for the provision of scientific advice to managers,
(2) the data needs of these models are quite well
understood, and (3) any model requires regular and prolonged
sampling to produce useful results. It is also clear that
past data collection in the Chesapeake Bay region has often
lacked the qualities needed: regularity, precision and
accuracy, representativeness, inclusiveness, and temporal
continuity. The sampling plans described in Chapter IV
of this document represent attempts to improve this
situation.
Since most models require several years' worth of data, it
will be a number of years after the initiation of appro-
priate data collection programs before a complete,
analytical stock assessment can be achieved. In the
interim, stock assessments will rely primarily on historical
information. As new information is added and modeling tools
developed, the reliability of assessments will increase.
During this phase of assessment development, the data that
33
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have been collected in Chesapeake Bay over past decades
should be made available for the best possible analysis by
the fishery science community as a whole. Although these
data may have many shortcomings, their analysis is necessary
to provide insight into the dynamics of our valuable living
marine resources. Finally, it is important to emphasize
that data collection and stock assessment activities are
best partitioned by biogeographic, rather than political,
boundaries. Fish /stocks are not restrained by state lines;
stock assessments can provide the best information if their
data and analyses are similarly extensive.
34
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CHAPTER IV. DATA COLLECTION PROGRAMS
The previous section emphasized the importance of
appropriate data collection to the process of stock
assessment. Many of the problems associated with our
present assessment capabilities are caused by inadequate
data. The following three sections on fishery dependent
programs, fishery independent programs, and recruitment
process studies will detail the type of improvements in data
collection programs that are necessary for stock assessment.
Fishery dependent programs rely on the monitoring of
commercial and recreational fisheries to determine trends in
abundance, as well as describe the characteristics of
fisheries. Fishery independent programs utilize
statistically designed surveys to collect the data used for
studying the dynamics of fishery stocks. Investigation of
recruitment processes is accomplished through short term
research projects and is intended to improve the
interpretation of statistics collected by longer term
programs. As such, all three programs should be viewed as a
complementary and comprehensive means of monitoring fishery
resources of the bay.
For these data collection programs a discussion of
techniques is presented. It is important to emphasize that
data collection programs will only be successful if they are
supported by appropriate data management and analysis. The
implementation chapter of this plan (Chapter 5) will discuss
the integration of data collection, management, analysis,
and documentation.
FISHERY DEPENDENT DATA COLLECTION
For the purposes of discussion, fishery dependent programs
for commercial and recreational fisheries will be treated
separately. Although data needs for both types of fisheries
are essentially the same, the techniques for data collection
are dramatically different due to the difference in number
of commercial and recreational fishermen. (There are on the
order of 10,000 commercial fisherman and 1,500,000
recreational fishermen fishing the bay each year.) This
difference, as well as other reasons, requires different
approaches to collection of statistics for commercial and
recreational fisheries.
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Commercial Fishery Statistics
Commercial fishery statistic programs involve the collection
of the following four types of data:
° Catch; meaning the amount of fish caught, including fish
killed and discarded during capture.
° Effort; meaning, admeasure of the amount of time and gear
used to catch the fish.
0 Biological parameters; meaning measures of length, weight,
age and sex of harvested fish.
0 Dockside value; meaning the amount of money paid to the
fisherman for his catch.
Catch, effort, and biological data are among the primary
inputs for most stock assessment models. Catch, effort, and
value data are the primary basis for making many management
decisions.
For both stock assessment and management the yearly
statewide or regionwide estimates must be disaggregated by
gear type, time (month or day) and water area. Many
classical stock assessment models do not require
disaggregated estimates of catch and effort. However, the
ability to describe distribution is a necessary component of
predictive and simulation models. For management,
disaggregated estimates are absolutely necessary for
evaluation of social and economic effects of proposed
regulations.
Within the limits which allow for collection of necessary
information, a commercial fishery statistics program should
impose as little burden on the industry as possible. An
unobtrusive system will have the best compliance and least
possible economic impact. Compliance will also be increased
by using a system which becomes a routine part of the
industry's practices.
Implementation of an adequate statistics program is
dependent on the appropriate legal, regulatory, and
licensing structures. Management agencies must have the
authority to collect the required information, to keep it
confidential, and to provide penalties when data is not
supplied. Without an adequate licensing system, it would be
next to impossible to organize a good fishery statistics
system. An ideal licensing system would require that each
gear type to be licensed and each individual would be
licensed separately for each gear type fished. For the bay
region, adequate authority and licensing structures exist,
however compliance and enforcement still pose difficult
36
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problems that must be faced. The implementation of revised
harvest reporting procedures will offer a good opportunity
for emphasizing improved compliance with reporting and
licensing laws.
Estimation of numerous variables in an accurate, precise and
timely manner, by species, year, month, day, water area and
gear type involves tradeoffs among some desirable
characteristics. , For example, a system which estimates
landings nearly in "real time" (as is necessary when quotas
are involved) will not be as accurate or precise as other
systems; or a system which produces disaggregated estimates
will be more expensive than one which produces only a yearly
estimate. For Chesapeake Bay fisheries, the highest priority
for stock assessment and management is to design a program
which will accomplish the following:
° Estimate landings and effort by species, year, month,
gear type and river system.
0 Estimate economic value by species, year, month, gear
type and river system.
0 Estimate length composition of the catch by year and
month.
Additionally, it may be necessary to develop capabilities to
develop more timely estimates. For some fisheries, year-end
estimates are probably sufficient; for others, month-end are
required; and for fisheries under a strict seasonal quota,
estimates at the end of each week or even day would be
necessary.
Measurement of Commercial Catch, Effort, and Biological Data
This section describes the units in which each of the data
types should be collected. In some cases, the units are
apparent (such as dollars for dockside value) while others
may be less so. In some cases, the best units may change
over time and space. Effort data is the most complex, with
several different measures of effort being possible for each
of several gear types.
Landings Estimates
These data are typically collected in units of weight
(pounds) or volume (bushels) for commercial fisheries and
numbers for recreational fisheries. Annual conversion
factors between weight and numbers should be established
from biological sampling of the catch.
Effort Estimates
For the most part, the required units are specific to each
gear type. For some fisheries and some analyses, labor
37
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units such as man-days or boat-hours may be sufficient, but
not ideal. The suggested "best" units for each gear type
are as follows.
0 Gill nets - net type (anchor, drift, stake) , length,
depth, thread size and time fished, by mesh size, for
each day.
° Pound nets - mesh -size of lead and pound, length of lead,
and number of hours between catches.
° Fyke nets, fish pots, crab pots - mesh size and number of
hours between catches.
° Haul seines - length and depth of net, smallest mesh
size, number of hours fished and number of hauls per day.
° Dredges (oyster, crab, clam). scrapes - size/weight of
gear and hours fished per day.
° Hand tongs. patent tongs. rakes - number of gear and
hours fished per day.
o
Divers. by hand - number of hours.
Trotlines and long lines - length of line, number of
baits, hours fished per day.
0
Purse seines - vessel size, length of nets.
0 Otter trawls - width of mouth, cod end mesh size, tow
duration and tow speed.
° Hook &. line - number of trips, hours per trip and number
of lines fished
Estimates of Biological Statistics
Individual organisms in the biological sample are weighed
and measured. In cases where accurate length/weight
relationships are established, only lengths may be taken.
If required, subsamples are taken to determine sex, collect
hard parts (scales, otoliths, fin rays, etc.) for laboratory
age determination and to collect gonads to develop maturity
and fecundity schedules. All sample sizes must be
sufficient to allow accurate characterization of the
harvests.
Biological statistics must also be coupled with the type of
gear used for harvest in order to determine the selectivity
of the gear and the representativeness of the sample. This
can be achieved either by taking samples at fish processing
points which can be associated with gear by interview, or by
38
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sampling directly on board commercial boats. The latter
will eliminate the uncertainty that may occur with dockside
samples, and also will provide useful information on catch
per unit effort (CPUE).
Techniques for Estimation
of Commercial Catch, Effort, and Value
A myriad of possible methods exist for estimation of
fisheries statistics. The following descriptions of many
possible alternatives is not all inclusive. All of the
methods described are in use or have been used in the
Chesapeake region.
Comparative Adjustment
Another cost efficient method, apparently still in use for
some fisheries in some areas, is for statistics agents to
visit a selection of fish dealers for information (usually
verbal) on the relative magnitude of recent catches. A
factor is calculated to adjust previous figures. For
example, if a consensus is developed that the harvest of
species X is down 10% from the previous year, last year's
figures are decreased 10% to calculate this year's harvest.
Advantages are in the area of cost and unobtrusiveness.
Disadvantages are inaccuracy, imprecision, no disaggregation
of estimates, no effort data.
Dealer Censuses
This is one of the most common methods of collecting
fisheries statistics throughout the world. Periodically
each licensed fish buyer is visited. The agent either
reviews the buyer's records or obtains a verbal or written
report on recent activities. Advantages of this system
include: relative unobtrusiveness; relatively low cost; when
no basket trade is involved, landings and value data can be
quite good; it maintains a direct agency contact with the
industry. Disadvantages include: lack of fishing effort
data; underestimates of landings when dealers don't
cooperate or in fisheries with large basket trades;
disaggregated data is more difficult to obtain than in a
system dependent on harvester reporting; daily estimates of
catch are not usually available.
Harvester Censuses
In this type of system, each licensed harvester is required
to send in a report on some periodic basis. Advantages
include: complete coverage of all licensed fisheries, i.e.
basket trade should be included in harvest estimates;
disaggregation of estimates can be accomplished on the
reporting form; effort data can be reported directly by the
harvester. Disadvantages include: this type of system is
39
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very intrusive and quite costly; recall and truthfulness are
questionable if there is no cross-checking audit system; due
to late submission of reports, the system will not be
timely; any failure to complete the census means an
automatic under-estimate of catch; separate systems would
usually have to be constructed for dockside value data.
Harvester Sample Surveys
In this type of /system, only a sample of fishermen are
periodically required to report their catch. From the
sample, an average catch per license is calculated and this
figure multiplied by total number of licenses to estimate
total catch. Advantages include: lower cost and less
intrusiveness than with a census; defined allowable error
ranges can be designed into the system; non-reporting is
less of a problem than in a census system; basket trade
should be included in harvest estimates; effort data is
obtainable directly from the harvester reports. Disad-
vantages include: disaggregation requires wider confidence
limits or larger sample sizes; recall and truthfulness can
be questionable.
Trip (Transaction) Ticket Censuses
This type of system requires that each day's fishing
activity is recorded on a transaction ticket, with a copy
sent to the management agency. The system can depend on
either the dealers or the harvesters to be responsible for
submission of the ticket. If dealers are to be responsible
then a requirement needs to included for harvesters to
report when their catch is not sold to a licensed dealer.
Advantages of this type of system include: every required
level of detail can be included; catch, effort and value can
all be collected in one system; completion of the trip
ticket should become routine and copies can be used for
records purposes for both harvesters and dealers; recall is
not a concern. Disadvantages include; the system is
relatively intrusive; agency cost is relatively high; the
system cannot be as timely as may be required for some
fisheries.
A Framework for Commercial Fishery Statistics Collection
The preceding section detailed the data requirements and
techniques for collection of data from commercial fisheries.
Current programs use these techniques, but in an
inconsistent manner. A satisfactory, baywide statistics
program is essential for stock assessment. The following
description is a proposal for developing an integrated
program. Over the next year, this proposal should be
critically reviewed for feasibility of implementation.
The foundation of the proposal is a mandatory commercial
40
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harvest reporting program. A transaction ticket system is
the suggested method of censusing commercial fishermen and
dealers. This method allows collection of information on
catch, effort, and dockside value at a high resolution of
time and area. Because of data processing backlogs, the
reporting system may need to be supplemented by informal
dealer surveys to determine estimates of catch during short
season, intense fisheries (striped bass, shad, black drum).
It is also likely' that effort information from the harvest
reporting forms will need to be verified by field surveys of
effort. Finally, catch estimates must be partitioned by age
(size), and sex for stock assessment, which will require a
comprehensive biological statistics program. A more
detailed accounting of these programs follow.
Trip Ticket System
Figure 3 shows a draft of a trip ticket which would be
completed by each fisherman at the end of a fishing day.
Such tickets would be provided to each fisherman in a three
part receipt book format similar to those used in res-
taurants and other cash businesses. One copy would go to
the management agency, one to the buyer and one to the
fisherman. Copies would be sent by the licensed fishermen
to the management agency weekly.
Figures 4 and 5 show samples of the coding systems which
would be provided with each booklet of trip tickets. These
would be printed on the inside and outside covers of the
booklet.
Careful record keeping would be necessary to insure that
every person was sending in reports in a timely manner.
Penalties must be assessed for those individuals who do not
comply. Fishermen must have an incentive for compliance;
that is, they must be shown that it is in their self
interest to provide the information.
A drawback to this system is that no census can ever be
complete; some fishermen will not comply, some paper will be
lost, etc. One possible way around this would be to treat
the entire trip ticket census as a large "sample" and expand
up to the total license count. The effects and validity of
this idea should be studied using existing data.
A transaction ticket system would generate large amounts of
paper. The only way to tabulate large amounts of paper in a
timely way is through automation. Computer machinery now
exists which is capable of reading human hand printed
figures with low error rates. Such machinery may well be a
cost effective alternative to key punching of data.
Randomized Dealer Telephone Survey
For those fisheries in which timeliness is a paramount
41
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concern and in which a constant or known fraction of the
catch is sold to dealers, rough estimates of total catch can
be estimated with a daily or weekly telephone survey of
seafood buyers. Once good mathematical relationships are
established between this system and the harvest reporting
system, it could be used to manage quota regulated
fisheries.
Surveys for Cross Checking Effort Data
For some fisheries, a system of vessel or net counts would
provide a good cross-check on participation levels. Such
fisheries would be those in which vessels and gear are
easily distinguishable.
Biological Data for Commercial Fisheries
Collection of biological data from commercial harvests is a
critical element of the fishery dependent programs. The
intercept point for biological sampling can either be on
board commercial boats or at dockside. For the latter,
landing sites are regularly visited and fish measured either
as they come off the boats or after they have been sold to a
dealer. For species in which length-at-age and length-weight
relationships have been established, length frequency data
would be sufficient, thus fish would not have to be
purchased. Purchase of some fish is probably unavoidable
since they would have to be dissected for sex determination
or other types of tissue samples. Recommendations for
biological sampling techniques for commercial pound nets has
been prepared by Chittenden (VIMS) under funding by CBSAC.
For sampling on commercial boats, CPUE data, in addition to
the data described above are, collected with little
uncertainty as to origin, gear type, and level of effort.
Recommendations for this type of program have been prepared
by Rothschild (CBL) for commercial blue crab fisheries in
the Bay.
42
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FIGURE 3. SAMPLE PISH TICKET
DAILY SEAFOOD CATCH TICKET
000001
l.a. FISHERMAN'S LICENSE NUMBER/
b. CAPTAIN'S LICENSE NUMBER (if
different)
2. DATE
month
day
3. GEAR TYPE USED (see front cover for codes)
4. TOTAL NUMBER OF PERSONS FISHING ON BOAT
5. a. AMOUNT OF GEAR (see front
cover for units)
b. use as necessary and as
directed on front cover
6. MESH SIZE (if appropriate)
7. HOURS FISHED TODAY
8. HpURS SINCE GEAR LAST FISHED
(if gear left set in water)
9. HARVEST AREA (see front flap for codes)
10. COUNTY LANDED
year
11. CATCH INFORMATION (see bacX flap for species unit codes)
12. FISHERMAN'S SIGNATURE
13. BVYER LICENSE NUMBER
(if appropriate)
LLJ
a. PRIMARY SPECIES SOUGHT
b. CATCH AND PRICE
SPECIES CODE | AMOUNT
1
1
|
1
1
I
UNT
1
TOTAL PRICE
D
8
(
1
<
<
<
|
I
I
43
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FIGURE 4. SAMPLE GEAR AND AREA CODING SCHEME FOR
FISH TICKET BOOKLETS
GEAR CODES
FINFISH
425 GILL NET, 'ANCHOR
470 GILL NET, DRIFT
480 GILL NET, STAKE
275 POUND NET, FINFISH
020 HAUL SEINE
310 FYKE NET
345 FISH POTS
210 OTTER TRAWL
125 PURSE SEINE
CRABS
330 CRAB POTS
680 TROTLINZS
770 SCRAPES
280 POUND NET, CRAB
390 BANK TRAP
XXX COLLAPSIBLE TRAP
703 DIP NETS
805 DREDGE
OYSTERS
840 HAND TONG
841 PATENT TONG
943 DIVING
815 DREDGE
CLAMS
803 DREDGE
855 RAKE
AMOUNT OF GEAR UNITS
a. b.
NET LENGTH (YARDS)
NET LENGTH (YARDS)
NET LENGTH (YARDS)
NUMBER OF NETS
NET LENGTH (YARDS)
NUMBER OF NETS
NUMBER OF POTS
WIDTH OF MOUTH
OF POTS
OF LIKE
OF SCRAPES
OF NETS
OF NETS
OF TRAPS
OF NETS
OF DREDGES
NET DEPTH (YARDS)
NET DEPTH (YARDS)
NET DEPTH (YARDS)
LENGTH OF LEAD
NUMBER OF HAULS
leave blank
leave blank
LENGTH OF TOW (HOURS)
NUMBER
LENGTH
NUMBER
NUMBER
NUMBER
NUMBER
NUMBER
NUMBER
leave blank
NUMBER OF BAITS
LENGTH OF LEAD
LENGTH OF LEAD
leave blank
leave blank
NUMBER OF TONGS
NUMBER OF TONGS
leave blank
leave blank
NUMBER OF DREDGES
NUMBER OF DREDGES
NUMBER OF RAKES
HARVEST AREAS
412 ASSAWOMAN BAY
012 ATLANTIC OCEAN
005 BIG ANNEKESSEX RIVER
537 BROAD.CREEK
013 CHES. BAY - N. OF WORTON PT.
025 CHES. BAY - N. OF BRIDGE £
S. OR WORTON PT.
262 NANTICOKE RIVER - ABOVE XXXXX
continued
44
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FIGURE 5. SAMPLE SPECIES CODING SCHEME FOR FISH
TICKET BOOKLET
FINFISH
0010 ALEWIVES
0230 BLUEFISH
SPECIES CODES
5170 YELLOW PERCH
5290 UNCLASSIFIED BAIT FISH
CRABS
7000 BLUE CRABS, HARD
7028 BLOB CRABS, SOFT
7029 BLUE CRABS, PEELER
7100 RED CRABS
7110 JONAH CRABS
CLAMS
7480 HARD CLAMS, PUBLIC
7510 HARD CLAMS, PRIVATE
7540 OCEAN QUAHOG
7630 SOFT CLAMS
7690 SURF CLAMS
CONCHES
7750 CONCHES
OYSTERS
OTHER SHELLFISH
8081 TERRAPIN
4180 STRIPED BASS
UNITS
P POUNDS
B BUSHELS
D DOZEN
E EACH
45
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Recreational Fishery Statistics
Fisheries in Chesapeake Bay also have a very active
recreational component. The effort, landings and economic
value have been reported for the commercial sector for many
years. However, until 1979, with the advent of the National
Marine Fisheries Service Marine Recreational Fishery
Statistics Survey (MRFSS), there was little data collected
from marine recreational fisheries. MRFSS was established
to meet the goals of the Magnuson Fishery Conservation and
Management Act of 1976, which required management of both
the commercial and recreational components of fisheries
within the 3-200 mile coastal zone. Prior to this there
were few and mostly localized surveys of the recreational
fisheries in Chesapeake Bay.
Management of the combined recreational and commercial
fisheries of Chesapeake Bay will rely on accurate estimates
of fishing pressure, catch, and biological parameters, such
as size-fecundity schedules and age and growth. Since, in
some fisheries the recreational harvest is thought to equal
or exceed the commercial catch, reliable estimates of effort
and harvest are of utmost importance for management of
Baywide fisheries. Equally important for the equitable
allocation of increasingly scarce resources is the knowledge
of the size and economic importance of the angling
community.
The recreational fisheries of Chesapeake Bay target species
which are seasonal or year round residents in the Bay (spot,
white perch, and flounder for example) and species that have
extensive coastal migration and are resident in the Bay as
adults for brief periods only (river herring, shad, and
black drum for example) . The type of statistical survey
sampling used to obtain information on catch and biological
parameters can be quite different for these two types of
target species. The first type can be assessed with a broad
temporal and geographical design, while the second type may
require surveys specifically designed for short and intense
fisheries.
Several methods exist for assessing recreational fishing
effort and harvest. Effort can be estimated from telephone
or mail surveys, or from contact interviews. The advantage
of obtaining effort information from telephone or mail
surveys is the reasonable cost of such surveys. They are
most efficient when a recreational fishing license list is
available to define the sampling frame for the study. Such
lists exist, of course, only in states that have mandated
licenses. The disadvantage of this method is that the
accuracy of the data is dependent on the anglers' memory
recall, which declines substantially within months of the
latest fishing trip.
46
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Effort can also be measured through aerial surveys or from
direct contact angler surveys. Aerial surveys are a cost-
efficient method for collecting effort estimates. They work
best for fisheries which can be discerned readily from other
recreational usage. Direct contact angler surveys can
provide information on both effort and catch. Their
advantage is the accuracy of information that is obtained.
Their disadvantage is relatively high cost and. Catch and
biological data are- also obtained through contact angler
surveys, where agents can actually identify, measure, and
weigh the fish. Contact surveys are used in conjunction
with telephone mail questionnaires and aerial surveys to
provide accurate catch data.
The most extensive survey currently being conducted in
Chesapeake Bay is the MRFSS. It is a dual-frame survey.
Effort is expanded from information obtained through
telephone interviews of coastal residents. The ratio of
fishing households to the total of households called is
used, in combination with U.S. Census data to estimate the
total number of fishing trips. Access intercept interviews,
where anglers are contacted at fishing access points, are
used to estimate fishing success rate, catch and biological
parameters. Additionally, the intercept interviews serve to
determine the effort for angling parties who live outside
the regional coastal area addressed through telephone
interviews.
Although the MRFSS is based on sound statistical design, the
intent of the survey is to give estimates of recreational
harvest and effort for broad geographic areas. For the
purposes of stock assessment and fisheries management in the
Bay it may be necessary to have better refined estimates.
In 1989, CBSAC will fund a study which will detail the
sampling requirements necessary to provide satisfactory
recreational fishing statistics for stock assessment. The
adequacy of the MRFSS and other survey designs for meeting
the requirements will be explored.
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FISHERY INDEPENDENT DATA COLLECTION
Fishery independent monitoring is the collection of data on
abundance, distribution, and biological characteristics of
fisheries stocks through the use of statistically designed
survey methods. The surveys are intended to complement and
supplement information produced by fishery dependent
monitoring of commercial and recreational fisheries. Thus,
the term 'independent' refers to the fact that data
collection is not dependent on harvests as a source of
biological statistics. The primary objectives of baywide
fishery independent surveys are as follows:
0 Collect data necessary to derive estimates of relative or
absolute, age-specific abundance for the tributaries and
mainstem bay. Highest priority life stages will likely
be pre-recruits (juveniles) and adult spawners.
° Collect other data useful in stock assessments to
determine age specific patterns of distribution, growth,
mortality, fecundity, sex and maturity.
Current methods for fishery independent sampling of marine
organisms have ranged from the conventional, eg. beach
seines for striped bass juvenile fish, to the
unconventional, air conditioner filters for blue crab
megalopae. A review of current methods can be found in the
Chesapeake Bay Program Biological Monitoring Atlas. A few
of the more common methods are found in Table 1.
It is not within the scope of this plan to specify all
aspects of survey designs that are required to provide the
fishery independent information necessary for stock
assessment. Nor is it likely that it could be done.
Uncoordinated surveys employing many if not all of the gears
listed in Table 1 are undertaken in the various
jurisdictions of the Bay every year. Some are long term
programs, others are shorter term experimental projects.
However, all have advantages and disadvantages. The task of
evaluating these programs is not simple and requires
thorough analysis to determine which programs should be
further developed for assessment purposes. This process
should occur during the course of individual stock
assessments. However, it is possible, and it will be the
purpose of this section, to review the primary alternatives
for development of a baywide core program for fishery
independent data collection.
In 1985, CBSAC began the process of reviewing existing
programs by funding projects concerning the juvenile finfish
trawl program in Virginia and the beach seine surveys used
in Maryland, Virginia, and the District of Columbia.
48
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Table 1. Representative gears for fishery independent
sampling.
LIFE STAGE
GEAR OR METHOD
USED FOR ENUMERATION
Meroplankton (eggs & larvae)
lined trawls
plankton nets
pumps/filters
Juveniles
fish/crabs
shellfish
trawls (lined/unlined)
beach seines
substrate samplers
'spat' collectors
Adults
fish/crabs
shellfish
trawls, gillnets, and
other commercial gears
scrapes
dredges
bottom grabs
Beach seine surveys are an integral part of striped bass
research and management in Virginia, Maryland, and the
District of Columbia and from that respect will continue for
the foreseeable future. Due to the recent investigation of
the survey, methodologies in all three jurisdictions have
been standardized.
Deliberations on a trawl program for the Bay continue. The
committee sponsored baywide trawl projects in 1988; it plans
to hold a workshop in Fall of 1988 to complete a final
design for a baywide trawl program. It is the collective
decision of the committee that a unified, consistent trawl
program should be one of the primary monitoring tools for
finfish and crab stock assessment.
The following outlines describe the recommended approaches
to fishery independent monitoring of finfish, crabs, and
shellfish.
49
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Finfish Monitoring - trawl, beach seine, and other gears
The Bay Trawl Study
Objectives:
° Collect information necessary to derive estimates of
abundance for juvenile and/or adult fish and crustaceans.
0 Spacial and temporal coverage of the survey will allow
documentation of habitat utilization by the species
sampled. Samples will be taken in all major tributaries
up to tidal freshwater, and in the main bay.
° Survey will provide biological samples for life history
studies and other concurrent scientific investigations.
0 Survey will be coordinated among jurisdictions to provide
long term, consistent estimates of abundance for the bay
and its tributaries.
Sampling Design: Stratified, randomized block design, bay
area will be broken into large geographic segments roughly
based on salinity and habitat characteristics. Within each
segment, random sampling will be stratified by depth.
Gear: Gear configuration is undecided. Current tests have
involved a 30' trawl and larger vessels (>40'). Smaller
trawls may also be needed to work in the upper tributaries
and shallow water areas. Gear will be selected within one
year and will be consistent among jurisdictions in sampling
areas with similar characteristics.
Temporal Resolution: Sampling will occur at least monthly.
As the survey develops sampling frequency may be increased
or decreased, dependent on abundance, during certain time
segments to improve the precision of estimates and the
efficiency of the survey.
Spatial Resolution: In Virginia plans are being made to
develop the survey initially in the tributaries with
expansion to the main bay. Depth ranges under consideration
are: 3'-12' unsampled unless by smaller trawl; 12'-30',
30'-42', >42'sampled by large trawls. In Maryland a similar
strategy is being developed. The District of Columbia will
use a smaller trawl.
Species: Weakfish, striped bass, croaker, spot, spotted
hake, white perch, silver perch, anchovy, hogchoker,
menhaden, eel, channel catfish, white catfish, toadfish,
silversides, alewife, blueback herring, blue crab
50
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Implementation: Maryland has proposed a five year trawl
project at CBL through W/B funds. Virginia plans to upgrade
the VIMS juvenile trawl survey through additional state
funding that was approved in the 1988 General Assembly.
Both projects will be in a developmental phase into 1989.
CBSAC proposes to hold a technical workshop beginning in
Fall of 1988 to aid in the development of the survey design.
Beach Seine Survey
Objectives:
° Collect data to derive estimates of abundance for young
of the year striped bass, and secondarily for other fish
using the near shore zone.
0 Document habitat utilization of striped bass, and other
species, in the important striped bass nursery areas.
0 Collect biological samples for life history studies.
0 Maintain a long term, consistent, cooperative survey for
striped bass assessment and management.
Sampling Design: Systematic sampling - fixed stations and
times
Gear: 100' x 4' beach seine, 1/4 inch mesh
Temporal Resolution: Samples are taken approximately once a
month from July through September (2 seine hauls per station)
Spatial Resolution: 22 stations in Maryland in the upper
bay, Choptank, Nanticoke, and Potomac Rivers. 18 stations
in Virginia in the James, York, and Rappahannock Rivers. 5
stations in the District of Columbia in the Potomac River.
Stations are limited to favorable seining sites in the
nearshore zone (0-3').
Species: Striped bass, white perch. Other species are
captured; Virginia's survey has recorded over 50 different
species. All are not representatively sampled.
Implementation: Beach seine surveys will continue as in the
past. Review of the survey and the associated historical
data base will occur during the course of baywide stock
assessment of striped bass. Additional work should
be funded to investigate the utility of the survey for other
species.
51
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Other Fishery Independent Finfish Surveys
Objectives: The objectives of other types of fishery
independent surveys would be the same as those listed for
the trawl and beach seine surveys. The primary objective of
alternate surveys is to collect information on finfish
species or life stages not obtained from the trawl or beach
seine surveys, or from fishery dependent programs.
Sampling Design: Will be dependent on specific objectives
of the survey. Statistical properties of proposed surveys
to be considered during planning.
Gear: Commercial gears employed with a statistical design -
gillnets, pound nets, fyke nets, trawls. Specialized
sampling devices - designed traps, electrofishing,
hydroacoustics, pop nets.
Temporal/Spacial Resolution: Dependent on survey
objectives.
Species: Dependent on perceived needs for management and
assessment.
Implementation: Of immediate concern, is the establishment
of a consistent survey for juvenile shad and herrings. The
gear of choice appears to be a boat mounted push net.
However, sampling difficulties and funding have thwarted a
consistent survey. It is recommended that a survey be
instituted in Maryland, Virginia, and the District of
Columbia.
Shellfish and Crab Monitoring
Blue Crab
Objectives:
° Collect post larval and juvenile blue crab data as an
index of potential recruitment.
0 Survey yearling and adult crabs as an index of abundance
and distribution.
0 Document and quantify habitat use (non-vegetated and SAV
beds) by life stages.
Sampling Design: Post larval stages can be collected and
abundance quantified in planktonic samples near the Bay
mouth and in marsh areas on megalopae collectors. Juveniles
and adults are taken by finfish trawls. Shallow SAV beds
require specialized sampling.
52
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Gear: Plankton nets, "megalopae screens", otter trawl, SAV
push or pop nets.
Temporal Resolution: Planktonic collections should be made
weekly during the "spawning" season; megalopae can be
collected daily during a 10-day period bracketing the full
moon; and juveniles and adults should be enumerated from
finfish trawling surveys on a monthly basis.
Spatial Resolution: Plankton collections can be made along
a transect across the Bay mouth. Stations should be spaced
to include inflow and outflow waters. Megalopae collectors
should be placed in representative marsh sites. Juvenile
and adult samples are collected from the stratified,
randomized finfish trawling.
Species: Blue crab
Implementation: Maryland and Virginia must continue their
commitment to the trawl surveys. Other juvenile sampling,
whether planktonic or post settlement, should be evaluated
as a part of a long term monitoring program. If these
additional programs are appropriate they should become part
of the core monitoring programs.
Oysters
Objectives:
0 Collect data on annual initial (summer) and surviving
(fall) spatfall on public oyster bars to derive an index
of recruitment.
° Survey spring and fall abundance of seed, small, and
market oyster, and predators (drills, mud crab,
flatworm) and fouling organisms on public oyster bars.
° Survey incidence of MSX and Dermo on selected public bars
to maintain an index of infestation.
0 Measure condition index (CI) of oyster on selected bars
as an index of health and spawning condition.
Sample Design: Systematic sampling of public oyster bars in
the mainstem Bay and tributaries. Repetitive samples should
be collected.
Gear: Hand tongs, patent tongs, dredge.
Temporal Resolution: Spatfall data should be collected
weekly from June through September; fall and spring survey
counts need only be sampled twice a year; disease incidence
53
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should be monitored weekly throughout the active infestation
periods; and CI needs to be measured monthly at
representative stations.
Spatial Resolution: Public oyster bars
Species: oyster, MSX, Dermo, tunicates, bryozoans, oyster
drill, pea crabs.
Implementation: Maryland and Virginia have monitoring
programs for spatfall and disease. Methodology should be
standardized and augmented as indicated by the objectives,
All oyster monitoring programs need to be infused with
additional funds.
Clams (hard and soft)
Objectives: Establish an annual survey of clams to
determine recruitment, abundance, distribution, and growth.
Sample Design: Stratified by depth, substrate, and
salinity, and randomized sampling on known or historic clam
beds.
Gear: Patent tong, dredge and hydraulic escalator dredge.
Temporal Resolution: Twice-annual sampling, weekly during
periods of recruitment.
Spatial Resolution: Baywide
Species: Hard clam, soft clam
Implementation: Neither Maryland nor Virginia have a
monitoring program to survey stocks of juvenile or adult
clams, nor are any programs under development to obtain an
index of recruitment. Because of the economic importance of
clams, these programs should be initiated.
54
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RECRUITMENT PROCESS STUDIES
The process of adding members to the exploitable stock is
termed the recruitment process. It covers the period in the
life history beginning at the egg stage and ending at the
onset of fishing mortality. In terms of population
dynamics, the period encompassing the recruitment process is
usually characterized by high mortality rates and large
year to year fluctuations in abundance. Environmental
variables, natural and man induced, play the most important
role in governing survival during these life stages.
Although predation, competition, cannabolism, and spawning
stock conditions will also influence survival to a greater
or lesser degree in some species. As such, recruitment
process research usually serves as the basis for determining
critical habitat requirements.
Generally, the effect of factors that determine the degree
of contribution of a given year's spawn to the exploitable
stock (termed yearclass strength) occurs in the first year
of life. These factors may be related to the abundance of
spawners that produced the yearclass or the abundance of
members of the yearclass themselves (density dependent
factors), or related to biological and habitat events
unrelated to their abundance or the abundance of their
parents (density independent factors). The objective of
recruitment process studies is to examine the extent to
which density dependent and density independent factors
influence the establishment of yearclass strength. As such
this type of research in part will seek to quantify the
effects of environment on resource production.
Approach
It is necessary to determine the pattern of survival during
the period of the recruitment process, and to relate this
pattern to trends in biotic and abiotic variables. The
relationship can be inferred from analysis of stock and
environmental monitoring data, or can be tested directly
through controlled laboratory and field studies.
Recruitment process research yields best results when it is
a combination of the two. Inferences drawn from analysis of
historical data sets can be used to formulate hypotheses for
laboratory and field testing.
Given the adequacy of available data sets, it is possible to
determine the potential influence of biotic and abiotic
factors on the recruitment process by examining the
historical relationships between stock size, fishing
mortality, environmental variables, pollutant loadings, and
habitat loss. This type of analysis, termed time series
analysis, requires a series of continuous measurements over
55
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a considerable length of time, since stock abundance varies
on annual cycles. Missing data, imperfect sampling, spatial
incongruities in measurements, and data sets with too few
observations are several of the major factors that inhibit
time series analysis. Some of these inhibiting factors may
be overcome by data interpolation, use of alternative
(proxy) data sets, and adjustment of the level of resolution
to a broader scale. An example of such an exercise, which
involves the white perch populations in the Choptank and
York rivers, has been documented by the CBSAC Data Set
Identification and Interpretation Working Group (see Related
Readings).
Data Needs
While retrospective analyses furnish important information
for understanding the factors that are important in the
recruitment process, they should not hinder efforts to move
forward with the collection of new, better suited data.
There often exists a tendency to conduct retrospective
analyses first, then design a sampling program to accomplish
what could not be accomplished using historical data sets,
leading to further and further delays in getting on with the
task. Based on the retrospective analyses performed to
date, scientists have gained a appreciation for the types of
data sets that would be most useful, given available
methodologies and techniques for time series analysis. These
generic criteria are summarized as follows:
0 Observations should be taken often enough to include
short term (seasonal) variability.
0 Enough locations should be sampled to cover spatial
variability.
° A long enough time series is necessary to show potential
long term changes or trends.
0 Observations need to be taken in a consistent manner. The
same techniques and gear should be used throughout the
time series.
0 The observations must be on a variable that is related in
a consistent manner to the parameter being estimated.
0 Choice of environmental variables to measure must make
good biological sense.
Usually one or more of these general criteria are not met.
Sampling programs focused on early life stages are typically
limited to certain habitat types (e.g., beach seines are
limited to beaches), have sampling frequencies that exceed
life stage durations, and do not coincide well with
56
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environmental monitoring programs in terms or spatial and
temporal resolution. These limitations result in failure to
detect causative relationships with any degree of
statistical confidence. With these problems in mind, it is
recommended that CBSAC continue to work with the Monitoring
Subcommittee of the Chesapeake Bay Program to ensure that,
where possible monitoring data sets include environmental
variables important to assessment and are established on
temporal and spatial .resolutions compatible with assessment.
Furthermore, where possible, programs designed to collect
data related to stock parameters (abundance, growth,
distribution, and mortality) should also collect relevant
environmental data.
Basic data needs relative to the study of recruitment
processes include life stage specific estimates of abundance
and development (growth) rates. To approximate the pattern
of survival through the life stages involved in the
recruitment process, age specific estimates for daily or
weekly cohorts within a life stage should be determined.
This will allow analysis of the age structure within a given
life stage (which may last from one day to several months),
and will enable comparison of survival rates to growth
rates.
Age specific estimates within the early life stages will
also enable determination of the approximate date of
spawning and allow comparison of the survivability of the
offspring to the condition of the parents. A significant
part of the recruitment process is related to the adult
population itself. Such factors as behavior, adult stock
structure (age, size, and sex ratio), genetic variability in
egg quality, and fecundity, influence the survivorship and
development of the offspring.
Selection of Species
Research on the recruitment process will involve dedication
of a significant amount of scientific resources because of
the type of information that needs to be retrieved. Initial
research efforts should focus on species considered
important in fisheries management. Commercial and
recreational finfishes of interest include striped bass,
American shad, river herring, yellow perch, white perch,
spot, croaker, and seatrout. Shellfish of interest include
blue crab and oyster, for which physical and environmental
factors have been suggested as the most important in
controlling the recruitment process.
Second priority should go to those species that appear to be
a significant factor in controlling the year class success
of commercial and recreational species. These ecologically
valuable species include potential predators, competitors,
57
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and prey, as well as plant species that are significant
components of critical habitats.
Conclusions
Research on the recruitment process is valuable to fisheries
management in that it supplies:
° Information on critical habitat requirements for
important species.
0 Estimates of potential strength of age classes that
will be entering the fishery.
° Information on the trend in the abundance of a species as
it relates to trends in the ecosystem.
0 A basis for evaluating habitat condition and alteration
of the environment.
° An improved understanding of the relationship between
stock size and recruitment.
Approaches to recruitment research have been developing
rapidly over the last several years. There are many
sampling and measurement difficulties inherent to the type
of work described. CBSAC recommends that any work
undertaken to investigate recruitment dynamics be carefully
planned before implementation. The Committee also proposes
to review project results in the Bay region and key projects
undertaken in other parts of the world to help better define
appropriate objectives and techniques for future research.
58
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CHAPTER V. IMPLEMENTATION
The stock assessment plan is oriented primarily to meet the
needs of state management bodies for information on the
status of the fishery resources. Assessments traditionally
relate status to /the effects of fishing, and provide some
basis for evaluating expected future yields and population
changes resulting from postulated fishing levels. This
usually applies to individual stocks defined by population
distribution and, to some necessary extent, by practical
fishery management considerations.
It is apparent that human development has resulted in
significant effects on the resources supporting the
fisheries. These effects must now be included in
assessments. Furthermore, alternative conservation and
management practices need to take into account implications
of the multispecies fisheries and ecosystem-related aspects
of natural factors of environment and species interactions.
These additional considerations require the collection of
more data, and the development and application of new
methodology. Achieving this increased sophistication in
assessments will take time, and requires that the first
steps be started immediately.
Although a rigorous accounting has not been made, there are
at least one hundred persons actively working on some aspect
of stock assessment in the Bay region. This tally would
include fisheries biologists, technical staff, academic
faculty, graduate research students and others working at
over twenty organizations in the Bay area. About three
million dollars per year are spent on research, monitoring,
and management programs that contribute to stock assessment.
A majority of these costs are covered by federal funds
(currently, approximately $2.5 million per year). An
obvious challenge for development of a baywide stock
assessment program is the coordination of these human and
monetary resources.
Implementation will be the shared responsibility of the
jurisdictions whose fishermen and other citizens benefit
from utilization of the resources and the Bay, and the
federal government. Implementation is obviously a
cooperative endeavor; the speed and effectiveness with which
it is carried out will be governed by factors outside the
scope of this plan. This section only offers advice on the
relative importance, need, and mechanisms to achieve the
objectives of stock assessment.
59
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A PROPOSED PROCESS
Figure 6 displays a basic flow of organizational
responsibilities and activities involving fishery stock
assessment in the Bay. To an extent, current assessment
practices follow this pattern, but they must be supplemented
and better coordinated to truly create an effective
Chesapeake Bay stock assessment process.
A noticeable feature of Figure 6 is the division of
responsibility between research and management organizations
in all jurisdictions. While there is no single authority by
which stock assessment is controlled, the formation of CBSAC
in 1985 was intended to solve the coordination problem for
assessment activities. The committee has the appropriate
membership, with the assistance of its work groups, to solve
technical stock assessment problems and it is a
recommendation of this plan to continue the committee with
further direction to begin a more active role in the
oversight of fisheries stock assessment activities in the
Bay.
The most effective way to integrate assessment activities
will be to encourage as much interaction as possible between
representatives from all jurisdictions on technical stock
assessment problems. During the first several years of
CBSAC this has been achieved through the activities of the
committee's workgroups. Their responsibilities have been
to review and analyze data sets for the purpose of better
understanding shortcomings in available data in order to
improve their utility and to suggest improvements for data
collection programs.
A stronger role by the working groups is needed to implement
the programs proposed herein. These groups would serve to
focus and coordinate among the large number of individuals
contributing to stock assessment. In addition to the
present workgroups, Status of Stock Knowledge (SOSK), Data
Set Identification & Interpretation (I & I) , and the Data
Base Coordination (DEC), new workgroups will be initiated
for finfish, oysters and blue crab. For this approach to
succeed, it is essential that the jurisdictions contribute
adequate staff time for preparation of technical documents.
For an interim period, it may be wise to have each workgroup
have one full time staff person.
The foregoing discussion generally describes some of the
organizational ideas that will be useful to build a stock
assessment process for the Chesapeake Bay. The most
important point is the continuation of CBSAC as a
cooperative means of overseeing stock assessment in the Bay.
60
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A revised terms of reference for the committee would be as
follows:
o Coordination, review, and oversight of data collection,
processing, archiving, and analysis.
o Preparation of annual Fishery Statistics and Status of
Stocks Reports, and periodic Status of Stock Knowledge
Report.
o Organize working groups and conduct workshops to complete
needed analytical assessments.
o Recommend research projects to provide information needed
for assessments.
A summary of the major features of a baywide stock
assessment program and recommended dates of implementation
follows.
Fishery Stock Assessment
Stock assessments will be overseen by CBSAC. Baywide
working groups for finfish, crabs, and oysters will be
established to coordinate and focus the multitude of stock
assessment scientists. The present working groups (SOSK,
I&I, DEC) will continue with the respective tasks of
reporting on status of Chesapeake Bay stocks, investigating
analytical techniques, and coordinating data management.
Annual cooperative reports documenting status of stocks and
fishery statistics, and periodic reports detailing
assessments will be produced. Assessments should begin as
soon as workgroups are established by CBSAC. Initial work
will depend on analysis of historical data. Special
attention should be directed in these initial assessments
towards critically evaluating all current and proposed
monitoring programs.
Commercial Fishery Statistics
The jurisdictions will improve existing statistics programs
to build a baywide fishery statistics program to obtain and
document annual, unbiased estimates of catch, landings, and
fishing effort. At a minimum the estimates will be broken
out by species for each type of gear, for each month of
catch, and for each water area. Actual procedures for
improved harvest reporting, fishing effort estimation, and
data management should be finalized within one year of the
approval of this plan and should strongly consider the
framework proposed in Chapter IV (particularly a mandatory
commercial tripticket system).
62
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Recreational Fishery statistics
Investigate the utility of statistics generated by the NMFS
Marine Recreational Fishery Statistics Survey (MRFSS) for
Bay stock assessment. Augmentation of that survey with
state and federal funds may be all that is necessary to
provide unbiased, annual estimates of recreational catch and
effort at a comparable resolution to commercial harvest
data. Review of the MRFSS survey and a plan for
recreational statistics collection should be completed by
December 1989.
Biological Characteristics of Harvest
One of the poorest aspects of current stock assessment
information is the lack of knowledge of age composition of
harvests. Biological samples must be collected annually
from both recreational and commercial harvests to obtain the
necessary data on species composition and age composition.
Improvements in age determination capabilities will be a
necessity for this program. Virginia plans a pilot program
for biological sampling of commercial harvests for July
1988; funding and staff have been approved. Maryland will
also begin a broader scale program after the initiation of
new harvest reporting procedures.
Fishery Data Management
An emphasis must be made on data sharing, particularly for
time series of routine harvest/ effort, and recruitment
data. Non-confidential data bases for each of the routine
data sets should be available for stock assessment within
six months of the end of each calendar year. Common data
files should be maintained for harvest, effort, and
recruitment data. Annual or biannual fishery statistic
reports should be used to document and disseminate this
information. Guidelines that increase access to research
data while protecting the obvious rights of individual
investigators should be developed. All pertinent data sets
will be properly documented and stored in a central data
center.
Fishery Independent Surveys
Recommendation is to adopt a long term, baywide trawl
program to obtain fishery independent estimates of abundance
and distribution of many of the important fish species and
crabs. The cooperative trawl project would be augmented as
necessary by other sampling methodologies to obtain
abundance estimates for species and life stages not captured
by the trawl. At least one important alternative method
will be beach seine surveys for anadromous fish. Pilot
projects for a trawl program were begun in 1988.
63
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Implementation of the program should begin by spring of
1989. In addition, analyses of existing fishery independent
survey data should be improved. This will occur to some
extent through the development of baywide assessment work
groups, but will also require the addition of staff to some
state programs (see Table 2).
Recruitment Process Studies
A variety of research projects to investigate recruitment
processes have been undertaken in the Bay region. Key
species have been striped bass, oyster, blue crab, spot,
croaker, and flounder. A review of Bay recruitment projects
and similar projects worldwide should occur in order to
better define research objectives and sampling designs that
would best determine the relative effects of environment and
fishing.
Biological Monitoring
The fishery dependent and independent data collection
techniques described in Chapter 4 serve as the basis for the
monitoring of fishery species, as well as other ecologically
important finfish, of the Chesapeake Bay. Assessments will
seek to use both long term monitoring information and short
term research information to understand the dynamics of
these living resources. Stock assessment data collection
programs will be coordinated with Bay monitoring programs
for water quality, and benthic and plankton communities. An
initial medium for reporting these data that will lead to a
description of the relationships between the environment and
fishery resources will be the biannual State of the Bay
Report.
Funding Considerations
The following table gives a rough accounting of staff and
budget needs to meet the recommendations within the plan
(Table 2). Also included in the table are potential funding
sources for the various activities. Notice that required
funding increases are not great, and that there are a number
of potential federal funding sources. Three actions that
would aid program development are (1) ensure a long term
funding base such as the CB8AC NOAA appropriation, (2) give
state agencies permission to use federally funded FTE's, and
(3) ensure adequate state funding for facilities, and for
staff when federal funds are not available. It is
recommended that individual jurisdictions develop thorough
program requests through their normal administrative
processes. The program changes and additional work required
to create a cooperative stock assessment program in the
time frames indicated will require the addition of the staff
positions shown in Table 2 by July 1989.
64
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RELATED READINGS
1982. Chesapeake Bay Fisheries Management Primer.
Chesapeake Bay Commission, Annapolis, MD. 28 pp.
1982. Report of Workshop on Chesapeake Bay Fisheries
Statistics. CRC Publication 107. Ill pp.
1982. Report of the Workshop on Blue Crab Stock Dynamics
in Chesapeake Bay. UM-CEES II ES-01-83. 168 pp.
1983. Choices for the Chesapeake: An action agenda.
Chesapeake Bay Program. 85 pp.
1983. Implementation of Recommendations on Chesapeake Bay
Statistics. Chesapeake Bay Cooperative Fisheries
Committee. 21 pp.
1984. An Action Program to Develop a Management System for
Chesapeake Bay Fisheries. UM-CEES (CBL) 84-7. 14 pp.
1985. Chesapeake Bay Stock Assessment Committee
Proceeding No.l. CBSAC. 53 pp.
1986. Chesapeake Bay Stock Assessment Committee
Proceedings No. 2. CBSAC. 82 pp.
1986. An Evaluation of Information Available for
Managing Chesapeake Bay Fisheries: preliminary
stock assessments, Volumes I and II.
UM-CEES (CBL) 85-29. 373 pp.
1987. Status of Stock Knowledge Bibliography. CBSAC SOSK
Working Group. 96 pp.
UPCOMING REPORTS
1988. Status of Chesapeake Bay Fishery Resources. CBSAC
SOSK Working Group.
1988. Status, Trends, Priorities, and Data Needs for
Chesapeake Bay Fisheries. Baywide Fishery Management
Work Group.
1988. Use of Historical Data Sets to Determine Causes of
Variabilty and Long Term Trends in the Abundance of
White Perch in the York and Choptank Rivers. CBSAC
I&I Working Group.
1988. Compendium of Stock Assessment Research Reports-FY85.
CBSAC.
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