United States Region III
Environmental Protection Agency Chesapeake Bay Program Office
Biological Evaluation
for the Issuance of Ambient Water
Quality Criteria for Dissolved
Oxygen, Water Clarity and
Chlorophyll a for the Chesapeake Bay
and Its Tidal Tributaries
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Biological Evaluation
for the Issuance of Ambient Water Quality Criteria
for Dissolved Oxygen, Water Clarity and Chlorophyll a
for the Chesapeake Bay and Its Tidal Tributaries
April 25, 2003
U.S. Environmental Protection Agency
Region III
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Contents
Page
Background
Summary of the Proposed Regional Criteria Guidance
Water Quality Standards
New and Refined Tidal Water Designated Uses
Chesapeake Bay Water Quality Criteria
Dissolved oxygen criteria
Water clarity
Chlorophyll a
Evaluation Area
Federal Listed Species Within the Evaluation Area . . .
Plants
Mammals
Birds
Fish
Reptiles
Mollusks
Insects
Status of Listed Species
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Manner in Which Regional Criteria Guidance May Affect the Shortnose Sturgeon
Water clarity
Chlorophyll a
Dissolved oxygen
Chesapeake Bay oxygen dynamics
Derivation of Chesapeake Bay dissolved oxygen criteria
Shortnose Sturgeon dissolved oxygen sensitivity
Dissolved oxygen criteria protective of shortnose sturgeon
Tidal Water Designated Use Habitats
Chesapeake Bay low oxygen: historical and recent past
Historical and potential sturgeon tidal habitats
Deep-channel habitats
Deep-water habitats
Salinity tolerances
Distribution studies
Chesapeake Bay salinity distributions
Life history of shortnose sturgeon
Status of shortnose sturgeon in the Chesapeake Bay
Delaware Chesapeake migratory corridor
Genetic findings
Field study results
Habitat quality benefits from dissolved oxygen criteria attainment
Recovery of the shortnose sturgeon
Findings
Summary and Conclusion
References
Tables and Figures
Table 1
Chesapeake Bay dissolved oxygen criteria
Table 2
Summary of Chesapeake Bay water clarity criteria for application to shallow-water bay
grass designated use habitats.
Table 3
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Chesapeake Bay narrative chlorophyll a criteria.
Figure 1 2
Illustration of the nutrient, sediment and dissolved oxygen impaired waterbodies in the
Chesapeake Bay watershed from the 1998 303(d) list.
Figure 2 11
Chesapeake Bay and its tidal tributaries.
Figure 3 28
Map of all U.S. Fish and Wildlife Service sturgeon capture location stations where
shortnose sturgeon were caught during June 1-September 30 between 1994- March 2003.
Figure 4 29
Map of all U.S. Fish and Wildlife Service sturgeon capture location stations where
shortnose sturgeon were caught year-round between 1994 and March 2003.
Figure 5 32
Map of summer averaged bottom water salinities <5 ppt based on Chesapeake Bay water
quality monitoring program data from 1996-2000.
Figure 6 33
Map of summer averaged bottom water salinities <15 ppt based on Chesapeake Bay
water quality monitoring program data from 1996-2000.
Figure 7 34
Long-term averaged spatial distribution of deep-water designated use habitats for
comparison only with figures 5 and 6 salinity distributions. Actual deep-water designated
use habitats will be determined based on pycnocline delineation using monthly
monitoring cruise data.
Figure 8 39
Locations of all the U.S. Fish and Wildlife Service fisheries-independent sturgeon
sampling stations where no sturgeon were caught.
Appendices
A. Ambient Water Quality Criteria for Dissolved Oxygen, Water Clarity and
Chlorophyll a for the Chesapeake Bay and Its Tidal Tributaries (Regional Criteria
Guidance).
B. Technical Support Document for the Identification of Chesapeake Bay Designated
Uses and Attainability.
C. List of Federally Endangered Species for Maryland, Virginia, Delaware and the
District of Columbia.
in
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Biological Evaluation
for the Issuance of Ambient Water Quality Criteria
for Dissolved Oxygen, Water Clarity and Chlorophyll a
for the Chesapeake Bay and Its Tidal Tributaries
U.S. Environmental Protection Agency
Region III
April 2003
The U.S. Environmental Protection Agency's (EPA) Region III Ambient Water Quality
Criteria for Dissolved Oxygen, Water Clarity and Chlorophyll a for the Chesapeake Bay and Its
Tidal Tributaries (Regional Criteria Guidance) is being evaluated. The EPA is voluntarily
continuing consultation with NOAA National Marine Fisheries Service in accordance with
Section 7 of the Endangered Species Act by issuing this biological evaluation.
The NOAA National Marine Fisheries Service, which is the federal agency with
responsibility for the shortnose sturgeon (Acipenser brevirostrum) under the Endangered Species
Act (ESA), has advised the EPA that shortnose sturgeon have been documented in various areas
of the Chesapeake Bay and its tidal tributaries and are, therefore, considered to be present in the
Bay.
BACKGROUND
The Administrator of the U.S. Environmental Protection Agency (EPA); the governors of
Maryland, Virginia and Pennsylvania; the Mayor of the District of Columbia; and the Chair of a
tri-state legislative body known as the Chesapeake Bay Commission signed the Chesapeake Bay
Agreement in 1987 (Chesapeake Executive Council 1987). A principal goal of that agreement
was a 40 percent reduction of nutrients (nitrogen and phosphorus) entering the Bay tidal waters
by the year 2000 from controllable point and nonpoint sources in the entire 64,000-square-mile
Bay watershed from levels being discharged in 1985. The agreement provided that once
achieved, this level would be maintained thereafter. Implementation of this goal was conducted
in a cooperative manner including actions under state laws primarily for best management
practice (BMP) implementation, and voluntary reductions from both point and nonpoint sources
encouraged by cost share grant programs. The EPA is participating in these activities pursuant
to Section 117 of the Clean Water Act.
Yet in spite of these efforts, nutrient and sediment enrichment related water quality
problems have persisted throughout the Chesapeake Bay and tidal tributaries (Figure 1) (U.S.
Environmental Protection Agency 2003b). Maryland's portion of the Chesapeake Bay and its
tidal tributaries were listed on its 1996 and 1998 Clean Water Act (CWA) Section 303(d) lists of
impaired waters. In May 1999, EPA Region III identified Virginia's portion of the Chesapeake
Bay and portions of several tidal tributaries on Virginia's 1998 CWA Section 303(d) list.
Delaware's tidal portion of the Nanticoke River and the District of Columbia's tidal Anacostia
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Figure 1. Illustration of the nutrient, sediment and dissolved oxygen impaired waterbodies in
the Chesapeake Bay watershed from 1998 303(d) list.
Source: U.S. EPA http://www.epa.gov/owow/tmdl/
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and Potomac rivers have also been listed on the Section 303(d) list. Shortly thereafter, a new
agreement, entitled Chesapeake 2000 was adopted by the Chesapeake Bay Executive Council in
response to a comprehensive assessment of the Bay's restoration needs and delineated an ambitious
list of new restoration commitments (Chesapeake Executive Council 2000). New York, Delaware
and West Virginia have been brought in as watershed partners committed to these Chesapeake Bay
water quality restoration goals through a six state memorandum of understanding with the EPA
(Chesapeake Bay Watershed Partners 2001).
Chesapeake 2000 lists the following specific actions as steps to achieve its water quality
goals for nutrients and sediment:
1. By 2001, define water quality conditions (i.e., criteria) necessary to protect aquatic
living resources and then assign load reductions for nitrogen, phosphorus and
sediment to each major tributary;
2. By 2002, complete a public process to develop and begin implementation of revised
Tributary Strategies to achieve and maintain the assigned loading goals;
3. By 2003, the jurisdictions with tidal waters will use their best efforts to adopt new or
revised water quality standards consistent with the defined water quality conditions.
Note that, though the actions still apply, the schedule has changed as follows:
• Final definitions of water quality conditions (i.e., criteria)-April 2003;
• Complete revisions to tributary strategies-April 2004; and
• Adoption of revised water quality standards-July 2005.
To implement and coordinate the above actions, the Chesapeake Bay Program formed a
Water Quality Steering Committee composed of senior water management policy representatives
from all seven watershed jurisdictions-New York, Pennsylvania, Maryland, District of Columbia,
Delaware, Virginia and West Virginia-EPA Region II, Region III and Headquarters, Chesapeake
Bay Commission, Interstate Commission on the Potomac River Basin, and the Susquehanna River
Basin Commission. A wide range of stakeholders including: regional governmental organizations,
the environmental advocacy community and wastewater treatment facility owners and operators
actively participated with the Committee. These partners and stakeholders have been meeting
several times a month over the past three years to meet the water quality commitments set forth in
Chesapeake 2000.
The "water quality conditions necessary to protect aquatic living resources" are being
defined through the development of EPA guidance for Chesapeake Bay specific water quality
criteria for dissolved oxygen, water clarity and chlorophyll a under the direction of the Chesapeake
Bay Program's Water Quality Steering Committee. Collectively, the EPA believes these three
water quality parameters provide the best and most direct measures of the impacts of too much
nutrient and sediment pollution on the Bay's aquatic living resources-fish, crabs, oysters, and
underwater bay grasses. The criteria are being published by EPA Region HI as Chesapeake Bay
specific water quality criteria guidance (U.S. Environmental Protection Agency 2003a).
The criteria are being issued pursuant to the Chesapeake Bay Program's statutory mandate
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under Section 117 (b)(2)(B) of the Clean Water Act to "implement and coordinate science, research,
modeling, support services, monitoring, data collection and other activities that support the
Chesapeake Bay Program." These criteria provide EPA's recommendations to states for use in
establishing water quality standards consistent with Section 303 (c) of the Clean Water Act,
focusing on the recovery and protection of aquatic life resources.
SUMMARY OF THE PROPOSED REGIONAL CRITERIA GUIDANCE
In order to achieve and maintain the water quality conditions necessary to protect the aquatic
living resources of the Chesapeake Bay and its tidal tributaries, EPA Region in has developed the
Regional Criteria Guidance. The EPA is issuing this guidance in accordance with Section 117(b) of
the Clean Water Act and in accordance with the water quality standards regulations (40 CFR Part
Bl). This document presents EPA's regionally-based nutrient and sediment enrichment criteria
expressed as dissolved oxygen, water clarity and chlorophyll a criteria, applicable to the Chesapeake
Bay and its tidal tributaries. This guidance is intended to assist the Chesapeake Bay states,
Maryland, Virginia and Delaware, and the District of Columbia in adopting revised water quality
standards to address nutrient and sediment-based pollution in the Chesapeake Bay and its tidal
tributaries.
EPA Region III has identified and described five habitats (or designated uses) that, when
adequately protected, will ensure the protection of the living resources of the Chesapeake Bay and
tidal tributaries. Those five uses (summarized below and described in detail in Appendix A and B)
provide the context in which EPA Region III derived adequately protective Chesapeake Bay water
quality criteria for dissolved oxygen, water clarity and chlorophyll a, which are the subject of the
Regional Criteria Guidance. Accurate delineation of where to apply these tidal water designated
uses is critical to the Chesapeake Bay water quality criteria (U.S. Environmental Protection Agency
2003a).
The Chesapeake Bay dissolved oxygen criteria vary significantly across the five refined tidal
water designated uses to fully reflect the wide array of species living in these different Bay habitats,
as reflected in Table 1.
The water clarity criteria reflect the different light requirements for underwater plant
communities that inhabit low salinity versus higher salinity shallow water habitats throughout the
Bay and its tidal tributaries. Table 2 provides an overview of the recommended light requirements
for water clarity criteria.
The EPA is providing the states with a recommended narrative chlorophyll a criteria
applicable to all Chesapeake Bay and tidal tributary waters (Table 3). The EPA encourages the
states to adopt numerical chlorophyll a criteria for application to those tidal waters where algal
related designated use impairments are likely to persist even after attainment of the applicable
dissolved oxygen and water clarity criteria. The Regional Criteria Guidance contains technical
information to support quantitative interpretation of the narrative chlorophyll a criteria.
The Regional Criteria Guidance is the product of a collaborative effort among the
Chesapeake Bay Program partners. They represent a scientific consensus based on the best
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available scientific findings and technical information defining water quality conditions necessary to
protect Chesapeake Bay aquatic living resources from effects due to nutrient and sediment over-
enrichment. Various stakeholder groups have been involved in their development, with
contributions from staff of federal and state government, local agencies, scientific institutions,
citizen conservation groups, business and industry.
The EPA conducted three reviews of the Regional Criteria Guidance. The third and final
public review of the Regional Criteria Guidance document was completed in January 2003 in
parallel to the second and final independent scientific peer review. The Regional Criteria Guidance,
comments from reviewers and responses to reviewers' comments will be available on the web on
April 25, 2003 at: http://www.chesapeakebav.net/bavcriteria.htm. A full copy of the Regional
Criteria Guidance is attached as Appendix A.
In addition to the Regional Criteria Guidance, EPA Region III distributed a draft Technical
Support Document for the Identification of Chesapeake Bay Designated Uses and Attainability
(T;chnical Support Document) for public review. The Technical Support Document provides
additional information for states to consider in the refinement of designated uses and modifications
of state water quality standards.
The Technical Support Document was made available for review and comment on
December 16, 2002. Comments received and response to reviewers' comments are available on the
web at: http://www.chesapeakebav.net/bavtsd.htm. A full copy of the draft Technical Support
Document was included in the draft BE previously submitted to NOAA National Marine Fisheries
and the U. S. Fish and Wildlife Service as part of the informal consultation. The final document is
expected to be completed on May 30, 2003. A full copy will be provided, upon publication next
month, as Appendix B.
WATER QUALITY STANDARDS
Water quality standards consist of 1) designated uses for the water body, 2) narrative or
numerical water quality criteria to protect those uses, and 3) an anti-degradation policy. Currently,
each state across the Chesapeake Bay and tidal tributary jurisdictional waters in the current
Maryland, Virginia, Delaware and the District of Columbia designated aquatic life uses to be
protected as part of their water quality standards. The Regional Criteria Guidance enables the states
to consider more specific, and in general, more protective aquatic life use refinements into criteria.
The Chesapeake Bay watershed states with tidally influenced Bay waters-Maryland, Virginia,
Delaware and the District of Columbia-are ultimately responsible for defining and formally
adopting a refined set of designated uses into their respective water quality standards.
New and Refined Tidal Water Designated Uses
The five new and refined Chesapeake Bay tidal water designated uses are proposed to more
fully reflect the different aquatic living resources communities inhabiting a variety of habitats and,
therefore, the different intended aquatic life uses of those tidal habitats. The tidal water designated
uses provide the context for deriving the Chesapeake Bay dissolved oxygen, water clarity and
chlorophyll a water quality criteria. Accurate delineation of where to apply these tidal water
designated uses is critical to effective application of the Chesapeake Bay water quality criteria. See
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the Technical Support Document (U.S. Environmental Protection Agency 2003b) for a more
detailed explanation of new and refined uses.
The migratory fish spawning and nursery designated use shall support the survival, growth
and propagation of balanced indigenous populations of ecologically, recreationally and
commercially important anadromous, semi-anadromous and tidal-fresh resident fish species,
including the federally listed shortnose sturgeon, inhabiting spawning and nursery grounds from
February 1 through May 31. It protects migratory fish during the late winter to spring spawning and
nursery season in tidal freshwater to low-salinity habitats. Located primarily in the upper reaches of
many Bay tidal rivers and creeks and the upper mainstem Chesapeake Bay, this use will benefit
several species including striped bass, perch, shad, herring and sturgeon.
The shallow-water bay grass designated use shall support the survival, growth and
propagation of rooted, underwater bay grasses necessary for the propagation and growth of
balanced, indigenous populations of ecologically, recreationally and commercially important fish
and shellfish inhabiting vegetated shallow-water habitats.
The open-water fish and shellfish designated use shall support the survival, growth and of
balanced, indigenous populations of ecologically, recreationally, and commercially important fish
and shellfish species inhabiting open water habitats. It is focused on surface-water habitats in tidal
creeks, rivers, embayments and the mainstem Bay, and protects diverse populations of sportfish,
including striped bass, bluefish, mackerel and sea trout, as well as important bait fish such as
federally listed shortnose sturgeon and important bait fish such as menhaden and silversides.
The deep-water seasonal fish and shellfish designated use shall support the survival,
growth and propagation of balanced, indigenous populations of ecologically, recreationally, and
commercially important fish and shellfish species inhabiting deep-water habitats from June through
September. It protects animals inhabiting the deeper transitional water-column and bottom habitats
between the well-mixed surface waters and the very deep channels. This use protects many bottom-
feeding fish, crabs and oysters, and other important species such as the bay anchovy.
The deep-channel seasonal refuge designated use shall protect the survival of balanced,
indigenous populations of ecologically important benthic infaunal and epifaunal worms and clams,
which provide food for bottom-feeding fish and crabs from June through September. Naturally low
dissolved oxygen conditions prevail in the deepest portions of this habitat zone, during the summer.
Chesapeake Bay Water Quality Criteria
Dissolved Oxygen Criteria
Current numeric state water quality criteria for tidal Chesapeake Bay waters aquatic life
protection require 5 mg literdissolved oxygen concentrations at all times (instantaneous or daily
minimum) throughout the year throughout all of tidal Bay waters - from the deep trench extending
down the center of the mainstem Chesapeake Bay to the shallows lining thousands of miles of
shoreline. Based on in-depth analyses of natural conditions and human-caused conditions that can
not be remedied, there are portions of deep-water Chesapeake Bay and its tidal tributaries that can
not achieve the current state dissolved oxygen standards during the June 1 through September 30
time frame (U.S. Environmental Protection Agency 2003b). Based on the scientific information set
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forth in the Regional Criteria Guidance and the Technical Support Document, the EPA has found
that the aquatic life uses in the deep-water and deep-channel habitats (summer only) have not and
will not require a 5 mg liter 4 dissolved oxygen levels for protection (see Appendix A and B and
discussions below). At the same time, the EPA found that migratory fish spawning and nursery
habitats require higher levels of dissolved oxygen (>5 mg liter"') to sustain aquatic life use during
the late winter to early summer time frame than provided by the current state water quality
standards. The Chesapeake Bay dissolved oxygen criteria are based on the clear scientific
evaluations of the specific needs of the aquatic living resources, where they live, and during which
time of the year they live there (the designated uses or habitats) and the level of oxygen needed
within each of the designated uses of the Bay tidal waters.
The Chesapeake Bay dissolved oxygen criteria vary significantly across the five refined tidal
water designated uses to fully reflect the wide array of species living in these different Bay habitats.
Table 1 summarizes the Chesapeake Bay dissolved oxygen criteria. For more detailed information,
including scientific data used in the development of the criteria, please review Chapter III in the
Ambient Water Quality Criteria for Dissolved Oxygen, Water Clarity and Chlorophyll A for the
Chesapeake Bay and Its Tidal Tributaries (Appendix A; U.S. Environmental Protection Agency
2003a). To review the recommended implementation procedures for this criteria, see Chapter VI in
the same document.
Water Clarity
Currently there are no numeric state water quality criteria that exist for water clarity with the
exception of the District of Columbia. The primary causes that have contributed to the loss of
underwater bay grasses in the Chesapeake Bay are nutrient over-enrichment and increased
suspended sediments in the water, and associated reductions in light availability. By applying
appropriate numeric water clarity criteria to the shallow-water bay grass designated use, attainment
of this criteria will improve the health and survival of underwater plant communities and, thus, the
quality of life and diversity of the fish and invertebrate species supported by these shallow-water
vegetated habitats (U.S. Environmental Protection Agency 2003a).
The Technical Support Document proposes that water clarity criteria should apply to
varying depths from 0.5 meters up to 2 meters (approximately 6.5 feet) depending on the area of the
Bay and tidal tributaries (U.S. Environmental Protection Agency 2003b). Areas where natural
factors (e.g. strong currents, rocky bottoms, shipping terminals) or permanent physical alternations
to shoreline (e.g., shipping terminals) would prevent underwater bay grass growth would be
excluded (Appendix B; U.S. Environmental Protection Agency 2003b).
The water clarity criteria reflect the different light requirements for underwater plant
communities that inhabit low salinity versus higher salinity shallow water habitats throughout the
Bay and its tidal tributaries (Table 2). For more detailed information, including scientific data used
in the development of the criteria, please review Chapter IV in the Ambient Water Quality Criteria
for Dissolved Oxygen, Water Clarity and Chlorophyll A for the Chesapeake Bay and Its Tidal
Tributaries (Appendix A; U.S. Environmental Protection Agency 2003a). To review the
recommended implementation procedures for this criteria, see Chapter VI in the same document.
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Table 1. Chesapeake Bay dissolved oxygen criteria.
Designated Use
Criteria Concentration/ Duration
Protection Being Provided
Temporal Application
Migratory fish
spawmng
and
nursery use
7-day mean > 6 mg liter"1
(tidal habitats with 0-0.5 ppt salinity)
Survival/growth of larvae/juvenile tidal fresh resident
fish; protective of threatened/endangered species.
February 1 -May 31
Instantaneous minimum > 5 mg liter"1
Survival and growth of larvae/juvenile migratory fish;
protective of threatened/endangered species.
Open water designated use criteria apply
June 1 - January 31
Shallow-water bay
grass use
Open water designated use criteria apply
year-round
Open-water fish and
shellfish use
30 day mean > 5.5 mg liter"1
(tidal habitats with 0-0.5 ppt salinity)
Growth of tidal fresh juvenile and adult fish; protective
of threatened/endangered species.
year-round
30 day mean > 5 mg liter"1
(tidal habitats with >0.5 ppt salinity)
Growth of larval, juvenile and adult fish and shellfish;
protective of threatened/endangered species.
7 day mean > 4 mg liter"1
Survival of open-water fish larvae.
Instantaneous minimum > 3.2 mg liter"1
Survival of threatened/endangered sturgeon species.1
Deep-water seasonal
fish and shellfish use
30 day mean > 3 mg liter"1
Survival and growth of Bay anchovy eggs and larvae.
June 1 - September 30
1 day mean > 2.3 mg liter"1
Survival of open-water juvenile and adult fish.
Instantaneous minimum > 1.7 mg liter"1
Survival of Bay anchovy eggs and larvae.
Open water designated use criteria apply
October 1 - May 31
Deep-channel
seasonal refuge use
Instantaneous minimum > 1 mg liter"1
Survival of bottom-dwelling worms and clams.
June 1 - September 30
Open water designated use criteria apply
October 1 - May 31
1. At temperatures considered stressful to shortnose sturgeon (>29°C), dissolved oxygen concentrations above an instantaneous minimum of 4.3 mg liter1 will
protect survival of this listed sturgeon species.
Source: U.S. Environmental Protection Agency 2003a.
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Table 2. Summary of Chesapeake Bay water clarity criteria for application to shallow-water bay grass designated use habitats.
Salinity
Regime
Water Clarity
Criteria as
Percent Light-
through-Water
Water Clarity Criteria as Secchi Depth
Temporal
Application
Water Clarity Criteria Application Depths
0.25
0.5
0.75
1.0
1.25
1.5
1.75
2.0
Secchi Depth (meters) for Above Criteria Application Depth
Tidal fresh
13%
0.2
0.4
0.5
0.7
0.9
1.2
1.3
1.4
April 1 - October 31
Oligohaline
13%
0.2
0.4
0.5
0.7
0.9
1.2
1.3
1.4
April 1 - October 31
Mesohaline
22%
0.2
0.5
0.7
1.0
1.2
1.4
1.7
1.9
April 1 - October 31
Polyhaline
22%
0.2
0.5
0.7
1.0
1.2
1.4
1.7
1.9
March 1 - May 31,
September 1 - November 30
Source: U.S. Environmental Protection Agency 2003a.
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Chlorophyll a
Maryland, Virginia, Delaware and District of Columbia's current water quality standards
do not include numeric chlorophyll a criteria. Chlorophyll a is an integrated measure of primary
production as well as an indicator of water quality. Chlorophyll a plays a direct role in reducing
light penetration in shallow-water habitat, thereby negatively affecting underwater bay grasses.
Uneaten by zooplankton and filter feeding shellfish, the microbial process that breaks down
excess dead algae removes oxygen from the water column. Phytoplankton assemblages can
become dominated by single species which represent poor food quality or even produce toxins
that impair the animals that feed directly on them. From a water quality perspective, chlorophyll
a is the best available, most direct measure of the amount and quality of phytoplankton and the
potential for reduced water clarity and low dissolved oxygen impairments.
The EPA is providing the states with a recommended narrative chlorophyll a criteria
applicable to all Chesapeake Bay and tidal tributary waters (Table 3). The EPA encourages the
states to adopt numerical chlorophyll a criteria for application to those tidal waters where algal
related designated use impairments are likely to persist even after attainment of the applicable
dissolved oxygen and water clarity criteria. The technical information supporting states'
quantitative interpretation of the narrative chlorophyll a criteria is published within the body of
the Chesapeake Bay water quality criteria document. For a full description and detailed
technical supporting documentation, please review Chapter V in the Ambient Water Quality
Criteria for Dissolved Oxygen, Water Clarity and Chlorophyll A for the Chesapeake Bay and Its
Tidal Tributaries (Appendix A; U.S. Environmental Protection Agency, 2003a). To review the
recommended implementation procedures for this criteria, see Chapter VI in the same document.
Table 3. Chesapeake Bay narrative chlorophyll a criteria.
Concentrations of chlorophyll a in free-floating microscopic aquatic plants (algae) shall not
exceed levels that result in ecologically undesirable consequences-such as reduced water
clarity, low dissolved oxygen, food supply imbalances, proliferation of species deemed
potentially harmful to aquatic life or humans or aesthetically objectionable conditions-or
otherwise render tidal waters unsuitable for designated uses.
EVALUATION AREA
The area evaluated for application of the EPA's recommended Regional Criteria
Guidance is the Chesapeake Bay and its tidal tributaries to the fall line (Figure 2).
FEDERAL LISTED SPECIES WITHIN THE EVALUATION AREA
Appendix C contains a listing of all Federally threatened and endangered species
compiled by the U.S. Fish and Wildlife Service and the NOAA National Marine Fisheries
Service in the four jurisdictions with tidal influenced Chesapeake Bay waters-Maryland,
Virginia, Delaware and the District of Columbia. The species listed include plants, mollusks,
fishes, reptiles, birds, insects and mammals. The level of information for each species varies.
Only a limited number of threatened or endangered species are aquatic dependent organisms.
For this evaluation the following aquatic and aquatic dependent species that still occur in the
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Chesapeake Bay and Major Rivers
Susquehanna^ 3 &
Chester
Potomac
Rappahannock
Mattaponi
Pamunkey
James
Choptank
V %
Nanticoke
Pocomoke
\York
Appomattox
LEIizabeth
Figure 2. Chesapeake Bay and its tidal tributaries.
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region and have been identified through correspondence with the Services were considered:
Plants-sensitive joint-vetch, swamp pink;
Mammals-humpback whale, finback whale, blue whale, right whale, sei whale,
sperm whale, West Indies manatee;
Birds-bald eagle, piping plover;
Fish-shortnose sturgeon, Atlantic sturgeon (state listed);
Reptiles-loggerhead sea turtle, Kemp's ridley sea turtle, leatherback sea turtle,
hawksbill sea turtle and green sea turtle;
Mollusks-dwarf wedge mussel; and
Insects-Puritan tiger beetle, northeastern beach tiger beetle.
Plants
The sensitive joint-vetch (Aeschynomene virginica) is found in Maryland and Virginia
(U.S. Fish and Wildlife Service 1992). It is an annual legume native to the eastern United States,
growing on the fringe of marshes or shores. The species occurs within the intertidal zone of
freshwater tidal river systems where populations are flooded twice daily. Its aquatic dependence
is, therefore, intertidal habitat. Its presence in a given marsh may be a factor of displacement by
aggressive, non-native plant species, hydrological conditions, salinity tolerances, and/or other
parameters. Sensitive joint-vetch seems to favor micro habitats where there is a reduction in
competition from other plant species. Bare to sparsely vegetated substrates appear to be a
habitat feature of critical importance for establishment and growth of this species. Almost every
population of sensitive joint-vetch is susceptible to hydrological changes (e.g., water withdrawal
projects), habitat loss and modification (e.g., through bank erosion), or other stressors caused by
development.
The swamp pink (Helonias bullata) is endangered in Maryland and Virginia, and
threatened in Delaware. The swamp pink is a distinctive perennial plant with thick stocky
rhizomes. It inhabits a variety of freshwater non-tidal wetlands, including spring seepages,
swamps, bogs, wet meadows and margins of small streams. The swamp pink does not usually
inhabit tidal wetland areas (L. Arroyo, personal communication, 2002). The major threat to the
species is loss and degradation of its wetland habitat due to encroaching development,
sedimentation, pollution, succession and wetland drainage. Activities that increase
sedimentation, pollutant runoff, or cause flooding of habitat should, therefore, be avoided.
Human foot traffic or vehicle traffic, as well as beaver dam building constitute other threats to
the swamp pink. Site conservation is the primary recovery plan for the swamp pink.
Mammals
Various marine mammals such as the blue whale (Balaenoptera musculus), sei whale
(Balaenoptera borealis), sperm whale (Physeter catodon), right whale (Balaena glacialis),
humpback whale (Megaptera novaeangliae) and finback whale (Balaenoptera physalus) occur
in ocean waters off the coast of Maryland and Virginia (NOAA National Marine Fisheries
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Service 1991a, 1991b, 1998b, 1998c). There is some evidence that healthy whales occasionally
use bay waters. For example, in 1994, two humpback whales were reported lunge fishing under
the Chesapeake Bay Bridge, according to David Scofield, Manager of Ocean Health Programs at
the Baltimore Aquarium (D. Scofield, personal communication, 2002). While whales are indeed
occasionally seen in the Chesapeake Bay, it is not considered critical habitat for them. Recovery
plans include maintaining and enhancing whale habitats, and identifying and reducing death,
injury or disturbance to whales caused by humans.
The West Indies manatee (Trichechus manatus latirostris) is another endangered
mammal species that sometimes visits the Chesapeake Bay. Typically manatees live in warm
marine/estuarine waters, and eat aquatic grasses, algae, mangrove leaves, and water hyacinths.
They usually migrate because of water temperature and salinity. In 1994, a manatee left the area
near Jacksonville, Florida on June 15, entered the Chesapeake Bay on July 4, and was spotted in
Rhode Island's waters on August 13. While water temperatures in these regions were unusually
warm in 1994, David Scofield at the Baltimore Aquarium says that there has been a manatee
sighting in the Bay every year since 1994 (D. Scofield, personal communication, 2002). Enough
of the sightings have been confirmed that scientists believe this wandering behavior may not be
as unusual as once thought. The major causes of mortality are from colliding with watercraft,
and getting stuck in flood gates and canal locks.
Birds
The bald eagle (Haliaeetus leucocephalus) is listed as threatened (U.S. Fish and Wildlife
Service 1990). Its aquatic dependence is due to the use of aquatic foraging areas for
consumption of aquatic organisms. Chesapeake Bay region bald eagles occupy shoreline habitat
of the Chesapeake and Delaware bays and their tributaries. Populations of bald eagles in the Bay
region have continued to increase since the recovery plan was written in 1990 (A. Moser,
personal communication, 2002). However, the eagle requires large blocks of undisturbed mature
forested habitat in proximity to aquatic foraging areas. The principal threat to its continued
recovery is habitat loss due to shoreline development and other land use changes. Chesapeake
Bay region eagles are also threatened by acute toxicity caused by continued use of certain
contaminants, shooting, and accidents. Recovery actions include protection of existing nesting,
foraging, and roosting habitat and reduction of mortality from environmental contamination.
The piping plover (Charadrius melodus melodus) is listed as threatened federally, and
also state listed as threatened in Virginia (U.S. Fish and Wildlife Service 1988). Approximately
100 pairs of piping plovers nest on Virginia's Atlantic barrier islands. They are uncommon
transients along the southern mainland coast and lower Chesapeake Bay. Plovers are rare
transients inland along the Potomac River and rare winter residents in Virginia. Piping plovers
arrive at breeding grounds in Virginia around mid-March and lay eggs from mid-April to early
July. They breed on sandy, gravel and/or cobbled coastal beaches in areas with little or no
vegetation. Piping plovers forage in intertidal zones and wrack lines of ocean beaches, washover
areas, mudflats, sandflats, coastal ponds, lagoons and salt marshes, eating marine worms, fly
larvae, beetles, crustaceans, mollusks and other invertebrates. Its numbers were drastically
reduced in the 20th century because of uncontrolled commercial and recreational hunting and egg
collecting in the 1900s, and dune stabilization and beachfront development after World War II.
Loss of habitat along with increased recreational use of beaches has caused further population
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declines. Today the populations are limited by predators (including dogs and cats), flooding of
the nest by rain or tidal overwash, development and beach stabilization, and pedestrian and Off
Road Vehicle traffic that inadvertently crush eggs or chicks. Continued protection of Virginia's
barrier islands for nesting is essential for recovery of this species in Virginia.
Fish
The Atlantic sturgeon (Acipenser oxyrhynchus oxyrhynchus) is listed as state
endangered in Delaware. Federally, the Atlantic sturgeon was placed on the candidate species
list in 1988 and again in 1998, though it was never listed (NOAA National Marine Fisheries
Service 1998d). It is being considered here due to the moratorium on all Atlantic sturgeon
harvests, adopted in 1997 by the Atlantic States Marine Fisheries Commission (Colligan et al.
1998).
The Atlantic sturgeon is an anadromous species, migrating from the ocean to fresh water
to spawn. It can live up to 60 years, and reach lengths of up to 14 feet, and weights of over 800
pounds. Sturgeon are typically bottom dwellers, using their snouts to root along the bottom for
benthic organisms such as molluscs, insects and crustaceans, which it sucks up with its
protrusive mouth. Currently, these sturgeon can be found in 32 rivers from Maine to Georgia,
with spawning occurring in at least 14 of these rivers.
The status of the Atlantic sturgeon in the Chesapeake Bay is not certain. There has been
no evidence of reproduction in the Maryland portion of the Chesapeake Bay for over 25 years
(Speir and O'Connell 1996). Recent evidence suggests limited spawning in the James and York
Rivers (NOAA National Marine Fisheries Service 1998d). The initial and most significant threat
to the Atlantic sturgeon was commercial fishing, since sturgeons are sought for their eggs
(caviar) as well as their flesh. Increased prevalence of hypoxia in the 20th century due to post-
World War II agricultural practices and residential development has caused sturgeon habitat
degradation in the 1900s (Secor and Niklitschek 2001). All sturgeon fisheries are now closed.
The shortnose sturgeon (Acipenser brevirostrum) is a Federally listed species.
Shortnose sturgeon was listed as endangered on March 11, 1967 (32 FR 4001), and they
remained on the endangered species list with the enactment of the Endangered Species Act in
1973 (NOAA National Marine Fisheries Service 1998a, 2002).
The National Oceanic and Atmospheric Administration's National Marine Fisheries
Service Shortnose Sturgeon Recovery Plan (Recovery Plan) indicates reports of its occurrence in
the Chesapeake system in 1876 (NOAA National Marine Fisheries Service 1998a). The
National Marine Fisheries Service Biological Opinion for the Washington Aqueduct Permit
(NOAA National Marine Fisheries Service 2002) states that other historical records of shortnose
sturgeon in the Chesapeake Bay include: the Potomac River (Smith and Bean 1899), the upper
Chesapeake Bay near the mouth of the Susquehanna River in the early 1980s, and the lower Bay
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near the mouths of the James and Rappahannock rivers in the late 1970s (Dadswell et al. 1984).1
The U.S. Fish and Wildlife Service Reward Program for Atlantic Sturgeon began in
1996. Shortnose sturgeon have been incidentally captured via this program. As of July 2002, 50
shortnose sturgeon were captured via the reward program in the Chesapeake Bay and its
tributaries-four from the lower Susquehanna River, two in the Bohemia River, six in the
Potomac River, two south of the Bay Bridge near Kent Island, one near Howell Point, one just
north of Hoopers Island, one in the Elk River, and two in Fishing Bay (Mangold 2003; Spells
2003; Skjeveland et. al. 2000). The remaining 31 shortnose sturgeon were captured in the upper
Chesapeake Bay north of Hart-Miller Island. These fish were captured alive in either
commercial gillnets, poundnets, fykenets, eel pots, hoop nets, or catfish traps (Mangold 2003;
Spells 2003; Skjeveland et. al. 2000).
In many river systems, Shortnose sturgeon appear to spend most of their life in their natal
river systems, only occasionally entering higher salinity environments. They are benthic
omnivores and continuously feed on benthic and epibenthic invertebrates including molluscs,
crustaceans and oligochaete worms (Dadswell 1979).
Shortnose sturgeon depend on free-flowing rivers and seasonal floods to provide suitable
spawning habitat. For shortnose sturgeon, spawning grounds have been found to consist mainly
of gravel or ruble substrate in regions of fast flow. Flowing water provides oxygen, allows for
the dispersal of eggs, and assists in excluding predators. Seasonal floods scour substrates free of
sand and silt, which might suffocate eggs (Beamesderfer and Far 1997).
Shortnose sturgeon spawn in upper, freshwater sections of rivers and feed and overwinter
in both fresh and saline habitats. In populations that have free access to the total length of a river
(absent of dams), spawning areas are located at the farthest accessible upstream reach of the
river, often just below the fall line (NOAA National Marine Fisheries Service 1998a).
Tributaries of the Chesapeake Bay that appear to have suitable spawning habitat for the
Chesapeake Bay shortnose sturgeon include the Potomac, Rappahannock, James, York,
Susquehanna, Gunpowder and Patuxent rivers (J. Nichols, personal communication, 2002). Still
other scientists believe that very little if any suitable spawning habitat remains for shortnose
sturgeon due to past sedimentation in tidal freshwater spawning reaches (Secor, personal
communication 2003; J. Musick, personal communication, 2003)
According to the Recovery Plan shortnose sturgeon are affected by habitat degradation or
loss (resulting, for example, from dams, bridge construction, channel dredging, and pollutant
discharges) and mortality (resulting, for example, from impingement on cooling water intake
screens, dredging and incidental capture in other fisheries) as principal threats to the species'
survival (NOAA National Marine Fisheries Service 1998a). The recovery goal is identified as
delisting shortnose sturgeon populations throughout their range, and the recovery objective is to
1 The EPA believes there is a potential that the Dadswell et. al. 1984 referenced observations at the mouths of the
James and Rappahannock are incorrect. The authors misidentify the York (as the James) on the map presented in
Figure 7 and give two markings, represented by dots in very up-estuary regions (one in York, one in the Mattaponi).
No details were given on the number of observations or source.
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ensure that a minimum population size is provided such that genetic diversity is maintained and
extinction is avoided.
Reptiles
Marine sea turtles include the loggerhead sea turtle (Caretta caretta), Kemp's ridley
sea turtle (Lepidochelys kempi), leatherback sea turtle (Dermochelys coriacea), hawksbill sea
turtle (Eretmochelys imbricata), and green sea turtle (Chelonia mydas). Sea turtles are
migratory; they enter the Chesapeake Bay in late May to early June when water temperatures
rise and depart between late September to early November. An estimated 3,000 to as many as
10,000 loggerhead turtles, and perhaps 500 Kemp's ridley sea turtles, use the Chesapeake Bay (J.
Musick, personal communication, 2002). Approximately 95 percent of the loggerheads found in
the Chesapeake Bay are juveniles, and the area from the mouth of the Bay to the Potomac River
serves as an important foraging area for this life stage. Loggerhead sea turtles tend to forage
along channel edges in the Bay and tidal rivers while Kemp's ridley sea turtles feed in the water
flats. Sea turtles in the Chesapeake Bay (mostly loggerheads and Kemp's ridleys) forage on
crustaceans (e.g., crabs) and mollusks. Threats to the turtles include, incidental takes, poaching,
pollution and marine habitat degradation. Recovery plans include protection of nesting habitats,
eliminating mortality from incidental catch in commercial fishing, and reduction of marine
pollution (NOAA National Marine Fisheries Service and U.S. Fish and Wildlife Service 1991a,
1991b, 1992, 1993; U.S. Fish and Wildlife Service and NOAA National Marine Fisheries
Service 1992).
Mollusks
The dwarf wedge-mussel (Alasmidonta heterodon) is endangered in Virginia and was
listed as Federally endangered in 1990. The dwarf wedge mussel is an Atlantic Coast freshwater
mussel, usually found in sand, firm muddy sand, and gravel bottoms in rivers of varying sizes
with slow to moderate current. To survive they need silt-free, stable stream beds and well-
oxygenated water that is pollutant free. No host fish are known for this species, but it is thought
that in some locations the host fish may be anadromous since these mussel populations have
been eliminated in rivers with dams. These mussels are found in Aquia Creek and the South
Anna and Nottoway rivers. The dwarf wedge mussel filter feeds on suspended detritus and
zooplankton. The dwarf wedge-mussel is salinity intolerant and, therefore, is mainly found in
freshwater habitats. They are mainly found in Connecticut and are not found in tidal areas (E.
Davis, personal communication, 2002). Habitat degradation is the greatest cause of this species'
decline. Industrial pollution, intensive recreational development, urban and agricultural
development, and siltation have adverse effects on this species.
Insects
The Puritan tiger beetle (Cicindela uritana) was listed as Federally threatened in 1990,
and is endangered in Maryland (U.S. Fish and Wildlife Service 1993). It is found in Kent, Cecil,
and Calvert counties. It occurs on open sand flats, dunes, water edges, beaches, woodland paths
and sparse grassy areas. Populations have declined due to habitat alterations associated with
human population growth, as well as inundation and disturbance of its shoreline habitat from
dam construction, riverbank stabilization, and other human activities. The beetle larvae, in
particular, are sensitive to natural and human-induced changes to beaches and bluffs, as well as
human traffic and water-borne pollution.
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The northeastern beach tiger beetle (Cicindela dorsalis dorsalis) is listed as threatened
in Maryland, and proposed threatened in Virginia (U.S. Fish and Wildlife Service 1994). It
occurs in over 50 sites within the Chesapeake Bay region. Northeastern beach tiger beetles are
rare beach-dwellers that occur on open sand flats, dunes, water edges, beaches, woodland paths,
and sparse grassy areas. The beetle is most vulnerable to disturbance during the larval stage,
which lasts two years. Larvae live in vertical burrows, generally in the beach intertidal zone
where they are particularly sensitive to destruction by high levels of pedestrian traffic, Off Road
Vehicles, and other changes due to coastal development and beach stabilization structures. It is
tolerant to aquatic changes and is more dependent on beach conditions for survival (B. Knisley,
personal communication, 2002)
STATUS OF LISTED SPECIES
For the reasons stated below, the EPA has determined through consultation with the U.S.
Fish and Wildlife Service and the NOAA National Marine Fisheries Service, that the issuance of
the Regional Criteria Guidance is not likely to adversely affect the listed species below (K.
Mayne, written correspondence, April 22, 2003, 2003; M. Ratnaswamy, written correspondence,
2003; M. Colligan, written correspondence, 2003). Therefore no further consultation is
necessary with respect to these species:
The swamp pink (Helonias bullata) does not usually inhabit tidal wetland areas. The
Chesapeake Bay and its tidal tributaries (evaluation area) are not considered important
habitat for this species.
• Blue whale (Balaenoptera musculus), sei whale (Balaenoptera borealis), sperm whale
(Physeter catodon), right whale (Balaena glacialis), humpback whale (Megaptera
novaeangliae), finback whale (Balaenopteraphysalus), and West Indies manatee
(Trichechus manatus latirostris) have been known to occasionally wander into the
Chesapeake Bay waters, however, it is not considered important habitat for them. The
major threat to these species is direct human physical contact.
• The dwarf wedge-mussel (Alasmidonta heterodon) is not found in the evaluation area.
• The northeastern beach tiger beetle (Cicindela dorsalis) is dependant on beach
conditions for survival.
• The Puritan tiger beetle (Cicindela uritana) is mainly threatened by human activities
such as population growth, disturbance of its shoreline habitat and construction of dams.
• Loggerhead sea turtle (Caretta caretta), Kemp's ridley sea turtle (Lepidochelys
kempi), leatherback sea turtle (Dermochelys coriacea), hawksbill sea turtle
(Eretmochelys imbricata), green sea turtle (Chelonia mydas) mainly use the Bay for
foraging during juvenile life stages. Sea turtle prey species will benefit from the Regional
Criteria Guidance.
The bald eagle (Haliaeetus leucocephalus) is a predator, and scavenger, exploiting a
variety of food sources such as birds, mammals, fish (consisting primarily of menhaden,
large gizzard shad, white perch and catfish) and waterfowl depending upon food
abundance. The Regional Criteria Guidance would encourage improved conditions for
these species of fish, particularly spawning habitat.
• The piping plover (Charadrius melodus melodus) are mainly found on the Atlantic coast
and are mainly threaten due to the depletion in prime nesting habitat areas.
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• The sensitive joint-vetch (Aeschynomene virginica) are mainly susceptible to water
withdrawal projects or habitat loss, modification, or degradation caused by development.
Therefore, the only endangered or threatened species under the NOAA Fisheries
jurisdiction in the evaluation area that will potentially be affected is the endangered shortnose
sturgeon (Acipenser brevirostrum) (K. Mayne, written correspondence, 2003; M. Ratnaswamy,
written correspondence, 2003; M. Colligan, written correspondence, 2003). No critical habitat
has been designated for the shortnose sturgeon (NOAA National Marine Fisheries Service
1998a).
MANNER IN WHICH REGIONAL CRITERIA GUIDANCE MAY AFFECT THE
SHORTNOSE STURGEON
Water Clarity
The recommended Chesapeake Bay water clarity criteria, if adopted by each state and
approved by the EPA would establish the minimum level of light penetration required to support
the survival and continued propagation of underwater bay grasses in both lower and higher
salinity communities (U.S. Environmental Protection Agency 2003a). The Regional Criteria
Guidance provides documentation which supports that attaining water clarity at the proposed
levels will improve underwater bay grass survival, growth and propagation, thus improving
habitat to fully support a diverse shallow water habitat. Based on the recommended criteria and
the evaluations for each listed species described above, which includes the habitat and spawning
areas of the species and threat to species recovery, the EPA has determined that the
recommended water clarity criteria will not likely adversely effect the listed species evaluated in
this document. Furthermore, the EPA has determined that the proposed water clarity criteria will
beneficially affect preferred habitat, spawning areas and food sources that will add substantially
in the recovery of the shortnose sturgeon.
Chlorophyll a
The recommended Chesapeake Bay narrative chlorophyll a criteria and technical
information supporting states' quantitative interpretation of the narrative criteria provides
concentrations characteristic of desired ecological trophic conditions and protective against
water quality and ecological impairments (U.S. Environmental Protection Agency 2003a).
These recommended concentrations are given to prevent reduced water clarity, low dissolved
oxygen, food supply imbalances, proliferation of species deemed potentially harmful to aquatic
life or humans, or aesthetically objectionable conditions. The Regional Criteria Guidance
provides documentation which indicate that water clarity and dissolved oxygen improve when
excess phytoplankton measured as chlorophyll a are significantly reduced, thus improving water
quality and critical aquatic habitat in the waters of the Chesapeake Bay and its tidal tributaries.
The EPA has determined that the recommended chlorophyll a criteria will not likely adversely
affect the listed species evaluated in this document. Furthermore, the EPA has determined that
the recommended chlorophyll a criteria will beneficially affect preferred habitat, spawning areas
and food sources that the listed species depends on.
Dissolved Oxygen
A set of dissolved oxygen criteria have been derived to protect Chesapeake Bay estuarine
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species based on the EPA's conclusions and scientific research on the different Bay habitats (see
chapters III and VI in Appendix A; U.S. Environmental Protection Agency 2003a). Oxygen
dynamics and natural low- to no-oxygen conditions were also fully considered in the
development of the refined tidal water designated uses (see Appendix B; U.S. Environmental
Protection Agency 2003b) which factor in natural conditions leading to low dissolved oxygen
concentrations.
Chesapeake Bay Oxygen Dynamics
Taking into account the natural processes that control oxygen dynamics is critical to
identifying the different Bay aquatic life habitats and establishing criteria reflective of natural
conditions and protective of each habitat. The Chesapeake Bay tends to have naturally reduced
dissolved oxygen conditions in its deeper waters because of its physical morphology and
estuarine circulation. As in other estuarine systems (e.g., Boynton et al. 1982; Nixon 1988;
Caddy 1993; Cloern 2001), the Chesapeake's highly productive waters combined with sustained
stratification, long residence times, low tidal energy and tendency to retain and recycle nutrients
set the stage for lower dissolved oxygen conditions. The mesohaline mainstem Chesapeake Bay
and lower reaches of the major tidal rivers have a stratified water column, which essentially
prevents waters near the bottom from mixing with more oxygenated surface waters. Recycling
of nutrients and water-column stratification leads to severe reductions in dissolved oxygen
concentrations during the warmer months of the year in deeper waters within and below the
pycnocline.
This reduction in dissolved oxygen generally results from a host of additional biological
and physical factors (e.g., Kemp and Boynton 1980; Kemp et al. 1992; Sanford et al. 1990;
Boynton and Kemp 2000). The annual spring freshet delivers large volumes of fresh water to
the Chesapeake Bay. The contribution of significant quantities of nutrients in the spring river
flows, combined with increasing temperatures and light, produces a large increase in
phytoplankton biomass. Phytoplankton not consumed by suspension feeders (such as
zooplankton, oysters and menhaden) sink to the subpycnocline waters, where they are broken
down by bacteria over a period of days to weeks (e.g., Malone et al. 1986; Tuttle et al. 1987;
Malone et al. 1988). This loss of oxygen due to bacterial metabolism is exacerbated due to the
onset of increased stratification, which restricts mixing with surface waters.
The Chesapeake Bay's nearshore shallow waters periodically experience episodes of low
to no dissolved oxygen, in part because bottom water has been forced into the shallows by a
combination of internal lateral tides and sustained winds (Carter et al. 1978; Tyler 1984; Seliger
et al. 1985; Malone et al. 1986; Breitburg 1990; Sanford et al. 1990). Low dissolved oxygen
conditions in shallow waters of the tidal tributaries are more often the result of local
production/respiration than the incursion of bottom waters. Climatic conditions such as calm
winds and several continuous cloudy days in a row can contribute to oxygen depletion in these
shallow water habitats. These habitats can be exposed to episodes of extreme and rapid
fluctuations in dissolved oxygen concentrations (Sanford et al. 1990). In depths as shallow as 4
meters, dissolved oxygen concentrations may decline to 0.5 mg liter"1 for up to 10 hours
(Breitburg 1990).
Diel cycles of low dissolved oxygen conditions often occur in non-stratified shallow
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waters where water-column respiration at night temporarily reduces dissolved oxygen levels
(D'Avanzo and Kremer 1994). In nearshore waters of the mesohaline mainstem Chesapeake
Bay, near-bottom dissolved oxygen concentrations are characterized by large diel fluctuations
and daily minima during the late night and early morning hours of July and August (Breitburg
1990).
The timing and extent of reduced dissolved oxygen conditions in the Chesapeake Bay
vary from year to year, largely driven by local weather patterns, the timing and magnitude of
freshwater river flow and concurrent delivery of nutrients and sediments into tidal waters, and
the corresponding springtime phytoplankton bloom (Officer et al. 1984; Seliger et al. 1985;
Boynton and Kemp 2000; Hagy 2002). In the Chesapeake Bay's mesohaline mainstem, these
conditions generally occur from June through September but have been observed to occur as
early as May and may persist through early October, until the water column is fully mixed in the
fall. The deeper waters of several major Chesapeake Bay tidal tributaries can also exhibit
hypoxic and anoxic conditions (Hagy 2002).
Derivation of Chesapeake Bay Dissolved Oxygen Criteria
The derivation of these criteria followed the methodologies outlined in the EPA's
Guidelines for Deriving Numerical National Water Quality for the Protection of Aquatic
Organisms and their Uses (U.S. Environmental Protection Agency 1985), the risk-based
approach used in developing the Ambient Aquatic Life Water Quality Criteria for Dissolved
Oxygen (Saltwater): Cape Cod to Cape Hatteras (U.S. Environmental Protection Agency 2000)
and the Biological Evaluation on the CWA 304(a) Aquatic Life Criteria as part of the National
Consultations, Methods Manual (National Consultation) (U.S. Environmental Protection
Agency, U.S. Fish and Wildlife Service and National Marine Fishers Service, in draft). The
resulting criteria specifically factored in the physiological needs and habitats of the Bay's living
resources and were structured to protect five distinct tidal water designated uses (U.S.
Environmental Protection Agency 2003a, 2003b).
Criteria for protecting the migratory fish spawning and nursery, shallow-water bay grass
and open-water fish and shellfish designated uses were set at levels to protect the growth,
recruitment and survival. Criteria applicable to deep-water seasonal fish and shellfish designated
uses were set at levels to protect shellfish and juvenile and adult fish, and to foster the
recruitment success of the bay anchovy. Criteria for deep-channel seasonal refuge designated
uses were set to protect the survival of bottom sediment-dwelling worms and clams. These
summer season deep-water and deep-channel designated uses take into account the limited
aquatic life uses due to the natural historic presence of low oxygen in these habitats and the
likelihood that such conditions may persist although significantly improved over present
conditions (U.S. Environmental Protection Agency 2003b).
Shortnose Sturgeon Dissolved Oxygen Sensitivity
Sturgeon in the Chesapeake Bay and elsewhere are more sensitive to low dissolved
oxygen conditions than most other fish. In comparison with other fishes, sturgeon have a limited
behavioral and physiological capacity to respond to hypoxia (multiple references reviewed and
cited by Secor and Niklitschek 2001, 2003). Sturgeon basal metabolism, growth, consumption
and survival are all very sensitive to changes in oxygen levels, which may indicate their
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relatively poor ability to oxyregulate. In summer, temperatures greater than 20°C amplify the
effect of hypoxia on sturgeon and other fishes due to a temperature-oxygen 'habitat squeeze'
(Coutant 1987). Deep waters with temperatures that sturgeon prefer tend to have dissolved
oxygen concentrations naturally below the minimum that they require. Sturgeon are therefore
either forced to occupy unsuitable habitats or have a reduction in habitat.
Several studies have directly addressed the lethal effects of hypoxia on sturgeon species
important to the Chesapeake Bay. Jenkins et al. (1993) examined the effects of different
salinities and dissolved oxygen levels on juveniles of the shortnose sturgeon (Acipenser
brevirostrum). The dissolved oxygen tests were all conducted at a mean temperature of 22.5°C.
The authors state:
Due to various constraints including limitations of facilities and test animals,
strictly controlled and standardized methods could not be followed in all tests.
The findings reported should be considered as preliminary until such time as
more rigorous testing can be accomplished.
In addition, the authors report nominal2 oxygen levels rather than those specific D.O.
levels experienced during each replicate experiment. All experiments were conducted in
freshwater. Still, there was strong evidence presented that younger fish were differentially
susceptible to low oxygen levels in comparison to older juveniles. Fish older than 77 days
experienced minimal mortality at nominal levels >2.5 mg/L, but at 2.0 mg liter"1 experienced 24
to 38 percent mortality. Younger fish experienced 18 to 38 percent mortality in the 3.0 mg liter"1
and >80% mortality in the 2.5 mg liter"1 treatment. Mortality of juveniles <11 days at treatment
levels >3.5 mg liter"1 was not significantly different than control levels. Because only nominal
levels were reported, the EPA could derive LC50 values based upon responses reported by
Jenkins et al. (1993).
Dissolved Oxygen Criteria Protective of Shortnose Sturgeon
More rigorous tests with shortnose sturgeon were recently performed using young-of-the-
year fish 77 to 134 days old (Campbell and Goodman 2003). Campbell and Goodman (2003)
present four 24-hr LC50 values for shortnose sturgeon (Acipenser brevirostrum). Three of these
are from tests with non-stressful temperatures (22-26°C) for this species. The fourth test was
conducted at 29°C and was considered to be a stressful temperature by the authors (L. Goodman,
personal communication, 2003). Fish from this fourth test also were exposed to temperatures as
high as 31°C during the acclimation period immediately preceding their exposure to hypoxia.
Since the data from the fourth test also include an effect due to temperature stress they should be
considered separately from that of the other three tests.
The most latest draft (December 2002) of the National Consultation on threatened and
2 The authors report that dissolved oxygen levels were monitored every 30 minute throughout the 6 hour
tests, and state that each parameter remained at 'satisfactory levels'. The dissolved oxygen values reported
are 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0 and 7.5 mg liter"1. Since up to five replicates were used with as many as
12 measurements, it seems very unlikely that these exact dissolved oxygen concentration values were
maintained consistently throughout all the tests.
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endangered species (being negotiated between the U.S. EPA, the U.S. Fish and Wildlife Service
and the National Marine Fisheries Service) states:
Where acute toxicity data are available for the species of interest, only these data will be
used for designating the LC50 for this species. If these data include more than one test,
the geometric mean of the LC50s of these tests will be used in risk calculations. If only
one toxicity test has been conducted, the lower 95% confidence interval of the LC50 from
this test will be used.
Following this guidance the final LC50 for shortnose sturgeon under ambient conditions
of non-stressful temperatures would be the geometric mean of 2.2, 2.2 and 2.6 mg liter"1 —2.33
mg liter"1. Under stressful temperatures the LC50 value that should be used would be 3.1 mg
liter"1 (this is the LC50 of the 29°C test, since the 3.1 mg liter"1 treatment resulted in exactly 50
percent mortality there was no 95 percent confidence interval) (Campbell and Goodman 2003).
Long-term exposures (10 days) of Atlantic sturgeon, Acipenser oxyrinchus, young-of-
the-year (150 to 200 days old) to 2.8 to 3.3 mg liter"1 at 26°C resulted in complete mortality over
a 10-day period in three of four replicates (Secor and Gunderson 1998). The fourth replicate
experienced 50 percent mortality. At 19°C and 2.3 to 3.2 mg liter"1, only 12 to 25 percent
mortality was recorded. There was insufficient data to calculate an LC50 for 19°C (was less than
2.70 mg liter-1, but could not determine how much less). However, based on survival data
present in Secor and Gunderson (1998), a 96-hr LC50 of 2.89 mg liter"13 was estimated for
Atlantic sturgeon at 26°C. This value is very similar to the 'high temperature' value of 3.1 mg
liter"1 calculated for shortnose sturgeon by Campbell and Goodman (2003). Data from
Niklitschek and Secor (2001) show that shortnose sturgeon are more tolerant of higher
temperatures than Atlantic sturgeon, which could explain why 26°C is not a stressful
temperature for shortnose sturgeon (Campbell and Goodman 2003), but is for Atlantic sturgeon
(Secor and Gunderson 1998). Alternately, the temperature difference between the two species
could be because the shortnose sturgeon were from Savannah River progeny and were held at
higher temperatures than the Atlantic sturgeon which came from Hudson River progeny.
Using the above data, the EPA calculated acute criteria for the protection of sturgeon
survival in the Chesapeake Bay under both non-stressful and stressful temperatures for habitats
appropriate for sturgeon use. The only LC50 value available for non-stressful temperatures that
meets the requirements for criteria derivation based on EPA's 1985 guidelines (U.S.
Environmental Protection Agency 1985) is the 24-hr 2.33 mg liter"1 calculated above from
Campbell and Goodman (2003). To be consistent with EPA guidelines, this value was used with
the original EPA Virginian Province saltwater dissolved oxygen criteria acute data set to
recalculate the Final Acute Value (FAV). The new FAV, 2.12 mg liter"1, is more protective than
the 1.64 mg liter"1 from the Virginian Province document, but not as protective as the 2.33 mg
3Based on daily dissolved oxygen data provided by the lead author, Dr.David Secor, University of Maryland Center
for Environmental Studies, Chesapeake Biological Laboratory, Solomons, Maryland.
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liter"1 value. Therefore, we default to the 2.33 mg liter"1 value, multiplying it by 1,384 to arrive at
a new CMC, 3.2 mg liter"1 (rounded to two significant figures). This value is expected to be
protective of sturgeon survival at non-stressful temperatures. Campbell and Goodman (2003)
indicate that most of the mortality for shortnose sturgeon occurs within the first 2 to 4 hours of a
test. Therefore, using this value as an instantaneous value should protect sturgeon under most
conditions.
A higher dissolved oxygen criterion would be needed in areas and times of the year
where sturgeon are to be protected and temperatures are likely to be considered stressful (e.g.,
29°C and above for shortnose sturgeon). The simplest approach is to use the LC50 value of 3.1
mg liter"1 from the fourth test of Campbell and Goodman (2003). Multiplying this by 1.38
results in a high temperature CMC for shortnose sturgeon of 4.3 mg liter"1.
To determine a criterion value that would also protect sturgeon from nonlethal effects in
the habitats for sturgeon use, bioenergetic and behavioral responses were considered which had
been derived from laboratory studies conducted on juvenile Atlantic and shortnose sturgeon
(Niklitschek 2001; Secor and Niklitschek 2001). Growth was substantially reduced at 40 percent
oxygen saturation compared to normal oxygen saturation conditions (greater than or equal to 70
percent saturation) for both species at temperatures of 20° C and 27° C. Metabolic and feeding
rates declined at oxygen levels below 60 percent oxygen saturation at 20° C and 27° C. In
behavior studies, juveniles of both sturgeon species actively selected 70 percent or 100 percent
oxygen saturation levels over 40 percent oxygen saturation levels. Based on these findings, a 60
percent saturation level was deemed protective for sturgeon. This corresponds to 5 mg liter"1 at
25° C. Therefore, a 5 mg liter"1 Chesapeake Bay dissolved oxygen criterion protecting against
adverse growth effects would protect sturgeon growth as well.
Tidal Water Designated Use Habitats
The migratory spawning and nursery and open-water designated uses are by their very
design and definitions protective of shortnose sturgeon. The deep-water and deep-channel
designated uses are seasonally applied to open-water habitats where and when water column
stratification prevents the free exchange of oxygenated waters with the surface mixed layer.
These two designated uses were not established to be protective of oxygen sensitive species like
sturgeon during the summer months in recognition of natural processes that make this habitat
unsuitable for such species during the June through September time frame as discussed below.
Chesapeake Bay Low Oxygen: Historical and Recent Past
Dissolved oxygen levels vary naturally in lakes, estuaries and oceans over varying
temporal and spatial scales due to many biological, chemical and physical processes. In
estuaries such as the Chesapeake Bay, freshwater inflow that influences water-column
stratification; nutrient input and cycling; physical processes such as density-driven circulation;
4This value is the geometric mean of the LC5/LC50 ratios from the Virginian Province document. The ratio for the
shortnose sturgeon tests from Campbell and Goodman (2003) was 1.30 (based on an analysis of raw data provided
by the co-author Larry Goodman, U.S. Environmental Protection Agency, Office of Research and Development,
Gulf Ecology Division, Gulf Breeze, Florida). To be consistent with the Virginian Province document, the EPA
applied the 1.38 ratio.
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and tides, winds, water temperature and bacterial activity are among the most important factors.
These processes can lead to large natural seasonal and interannual variability in oxygen levels in
many parts of the Chesapeake Bay and its tidal tributaries.
Superimposed on this natural dissolved oxygen variability is a progressive increase in the
intensity and frequency of hypoxia and anoxia over the past 100 to 150 years, most notably since
the 1960s. This human-induced eutrophication is evident both from instrumental data and
geochemical and faunal/floral 'proxies' of dissolved oxygen conditions obtained from the
sedimentary record.
The instrumental record, while incomplete prior to the inception of the multi-agency
Chesapeake Bay Monitoring Program in 1984, suggests that as early as the 1900s to 1930s (Sale
and Skinner 1917; Newcombe and Home 1938; Newcombe et al. 1939) and especially since the
1960s (Taft et al. 1980; Hagy 2002), summer oxygen depletion has been recorded in the
Chesapeake Bay. Officer et al. (1984), Malone (1992), Harding and Perry (1997) and Hagy
(2002) provide useful discussions of the instrumental record of dissolved oxygen and related
parameters such as chlorophyll a across this multi-decadal data record.
At issue is whether, and to what degree, dissolved oxygen reductions are a naturally
occurring phenomenon in the Chesapeake Bay thereby creating habitats at certain times of year
that are unsuitable for species including the sturgeon. Long sediment core (17 to greater than 21
meters in length) records indicate that the Chesapeake Bay formed about 7,500 years ago
(Cronin et al. 2000, Colman et al. 2002) when the rising sea level after the final stage of
Pleistocene deglaciation flooded the Susquehanna channel. The modern estuarine circulation
and salinity regime probably began in the mid- to late Holocene epoch, about 4,000-5,000 years
ago (in the regional climate of the early Holocene, the Chesapeake Bay's salinity differed from
that of the late Holocene). This is based on the appearance of 'pre-colonial' benthic
foraminiferal, ostracode and dinoflagellate assemblages. It is against this mid- to late Holocene
baseline that we can view the post-European settlement and modern dissolved oxygen regime of
the Chesapeake Bay.
During the past decade, studies of the Chesapeake Bay's late Holocene dissolved oxygen
record have been carried out using several proxies of past dissolved oxygen conditions, which
are preserved in sediment cores that have been dated using the most advanced geochronological
methods. These studies, using various indicators of past dissolved oxygen conditions, are
reviewed in Cronin and Vann (2003) and provide information that puts the monitoring record of
the modern Chesapeake Bay into a long-term perspective and permits an evaluation of natural
variability in the context of restoration targets. The following types of measurements of oxygen-
sensitive chemical and biological indicators have been used: nitrogen isotopes (Bratton et al.,
2003); biogenic silica and diatom communities (Cooper and Brush 1991; Cooper 1995; Colman
and Bratton 2003); molybdenum and other metals (Adelson et al. 2000; Zheng et al., 2003); lipid
biomarkers; acid volatile sulfur (AVS)/chromium reducible sulfur (CRS) ratios; total nitrogen
and total organic carbon (Zimmerman and Canuel 2000); elemental analyses (Cornwell et al.
1996) and paleo-ecological reconstructions based on dinoflagellate cysts (Willard et al. 2003);
and benthic foraminiferal assemblages (Karlsen et al. 2000). Although space precludes a
24
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comprehensive review of these studies, and the time period studied and level of quantification
vary, several major themes emerge, which we summarize here.
First, the 20th century sedimentary record confirms the limited monitoring record of
dissolved oxygen, documenting that there has been a progressive decrease in dissolved oxygen
levels, including the periods of extensive anoxia in the deep-channel region of the Chesapeake
Bay that have been prominent during the last 40 years. Most studies provide strong evidence
that there was a greater frequency or duration of seasonal anoxia beginning in the late 1930s and
1940s and again around 1970, reaching unprecedented frequencies and/or duration in the past
few decades in the mesohaline Chesapeake Bay and the lower reaches of several tidal tributaries.
Clear evidence of these low dissolved oxygen conditions has been found in all geochemical and
paleo-ecological indicators studied principally through their great impact on benthic and
phytoplankton (both diatom and dinoflagellate) communities.
Second, extensive late 18th and 19th century land clearance also led to oxygen reduction
and hypoxia, which exceeded levels characteristic of the previous 2,000 years. Best estimates
for deep-channel mid-bay seasonal oxygen minima from 1750 to around 1950 are 0.3 to 1.4-2.8
mg liter"1 and are based on a shift to dinoflagellate cyst assemblages of species tolerant of low
dissolved oxygen conditions. This shift is characterized by a four- to fivefold increase in the
flux of biogenic silica, a greater than twofold (5-10 milliliter"1) increase in nitrogen isotope ratios
(15N) and periods of common (though not dominant) Ammoniaparkinsoniana, a facultative
anaerobic foraminifer. These patterns are likely due to increased sediment influx and nitrogen
and phosphorous runoff due to extensive land clearance and agriculture.
Third, before the 17th century, dissolved oxygen proxy data suggest that dissolved oxygen
levels in the deep channel of the Chesapeake Bay varied over decadal and interannual time
scales. Although it is difficult to quantify the extremes, dissolved oxygen probably fell to 3-6
mg liter"1, but rarely if ever fell below 1.4-2.8 mg liter"1. These paleo-dissolved oxygen
reconstructions are consistent with the Chesapeake Bay's natural tendency to experience
seasonal oxygen reductions due to its bathymetry, freshwater-driven salinity stratification, high
primary productivity and organic matter, and nutrient regeneration (Boicourt 1992; Malone
1992; Boynton et al. 1995).
In summary, the main channel of the Chesapeake Bay most likely experienced reductions
in dissolved oxygen before large-scale post-colonial land clearance took place, due to natural
factors such as climate-driven variability in freshwater inflow. However, this progressive
decline in summer oxygen minima, beginning in the 18th century and accelerating during the
second half of the 20th century, is superimposed on past and present interannual and decadal
patterns of dissolved oxygen variability. Human activity during the post-colonial period has
caused the trend towards hypoxia and most recently (especially post-1960s) anoxia in the main
channel of the Chesapeake Bay and some of its larger tributaries. The impact of these patterns
has been observed in large-scale changes in benthos and phytoplankton communities, which are
manifestations of habitat loss and degradation.
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Historical and Potential Sturgeon Tidal Habitats
Atlantic and shortnose sturgeon probably most recently colonized the Chesapeake Bay
5,000-8,000 years ago after the last glaciation, when climate and the watershed's hydraulic
regime became more stable (Custer 1986; Miller 2001). The Chesapeake Bay during this period
already exhibited the two-layer circulation pattern. Thus, we should expect that deep-channel
habitats during periods of strong stratification were hypoxic during the past 5,000 years, albeit
not at the same spatial extent or severity that has occurred over the past 50 years (Officer et al.
1985; Cooper and Brush 1991). Atlantic sturgeon in other estuarine and coastal systems will use
habitats greater than 15 meters in depth (see below), but these other systems do not exhibit the
same characteristics of estuarine circulation, watershed areal extent and bathymetry that
contributes to natural deep-water and deep-channel hypoxia in the mesohaline Chesapeake Bay.
Deep-Channel Habitats
The geochemical, paleoecological, and instrumental record of the 20th century indicates
that deep-channel regions have not served as potential habitats for sturgeon because seasonal
(summer) anoxia and hypoxia have occurred most years, reaching and sustaining levels below
those required by sturgeon. Hypoxia, and probably periodic, spatially-limited anoxia, occurred
in the Chesapeake Bay prior to the large-scale application of fertilizer, but since the 1960s
oxygen depletion has become much more severe, prohibiting sturgeon use of this habitat during
summer months (Hagy 2002).
Analysis of recent U.S. Fish and Wildlife Service sturgeon capture location data showed
absence of sturgeon occurrences in deep-channel habitats during summer months (June 1
through September 30), but substantial numbers of occurrences in these same habitats during
other seasons (U.S. Environmental Protection Agency 2003b). Based upon the recent relevant
history of the Chesapeake Bay ecosystem, the deep-channel regions in summer are not
considered sturgeon habitats.
Deep-Water Habitats
Deeper water-column regions may continue to support foraging, temperature refuges, and
migration corridors for sturgeons during times in the absence of strong water-column
stratification which naturally result in dissolved oxygen concentrations well below saturation due
to restrictions in mixing with the well-oxygenated surface mixed layer. In other estuarine and
coastal systems where strong water-column stratification does not occur to the degree observed
in the Chesapeake Bay and its tidal tributaries, both sturgeon species are known to use deep-
water habitats in summer months as thermal refuges (see section titled "Life History of
Shortnose Sturgeon").
The water column in the mesohaline Chesapeake Bay mainstem and the mesohaline
lower tidal reaches of several major tributaries (Chester, Patapsco, Patuxtent, Potomac and
Rappahannock river) stratifies to the point where within pycnocline (deep-water) and below
pycnocline (deep-channel) waters are effectively prevented from receiving oxygenated waters
from the overlying surface mixed layer (open-water) during the summer months. These
mesohaline (>5-18 ppt) waters are also far enough removed from the free flowing rivers and the
ocean to prevent re-oxygenation through the inflow of oxygenated bottom waters. During the
period 1990-1999, very little summer time deep-water habitat was predicted to support sturgeon
26
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production based upon a bioenergetics model, due principally to pervasive hypoxia (Niklitschek
and Secor, in review). Further, sturgeons are able to behaviorally respond to favorable gradients
in dissolved oxygen (Secor and Niklitschek 2001) and, thus, will avoid the naturally lower
dissolved oxygen waters.
Recent fisheries dependent and independent data synthesized by the U.S. Fish and
Wildlife Service (Mangold 2003; Spells 2003; Skjeveland et. al. 2000) did not show substantial
overlap during summer months between deep-water regions and shortnose sturgeon occurrences.
The EPA recognizes this data base contains fisheries dependent data collected through
incidental catch by gear (i.e., pound nets) deployed generally in waters less than 7 meters in
depth.
Figure 3 illustrates shortnose sturgeon capture locations during the June 1 through
September 30 timeframe with Figure 4 illustrating the locations of all 50 shortnose sturgeon
captures in Chesapeake Bay throughout the year since 1994 through March 2003. Outside of the
June 1 through September 30 time frame, shortnose sturgeon captures were reported across all
tidal water habitats, including habitats seasonally designated as deep water or deep channel, but
protected as open-water habitats from the beginning of October through the end of May.
Through an in-depth analysis of the 400 station, 1400 individual sturgeon (both Atlantic and
shortnose sturgeon) U.S. Fish and Wildlife Service captures database, no recorded shortnose
sturgeon captures overlapped with the seasonally defined deep-water habitat.
Based upon this analysis, it does not appear likely that habitat found within pycnocline
deep water would comprise 'potential'habitats for sturgeons during periods of strong water
column stratification limiting exchange with overlying, more oxygenated waters. In the absence
of strong water column stratification, these deeper depth water column habitats are considered
open water habitat and comprise 'potential' habitats for sturgeons.
Salinity Tolerances
During their first year of life, shortnose sturgeon tend to occur in fresh water (Dovel et al.
1992; Haley 1999) but can tolerate salinities up to 15 ppt (Jenkins et al. 1993; Niklitschek 2001).
Extensive observational and experimental evidence points toward shortnose sturgeon
concentrating in habitats with less than 5 ppt for all life history stages during summer months
(Dadwell 1984; Dovel et al. 1992; Geogehan et al. 1984; Brundage and Meadows 1982; Collins
and Smith 1996; Bain 1997; Haley 1999). Laboratory experiments also showed that young-of-
the-year Atlantic sturgeon are more likely to survive in salinities greater than or equal to 15 ppt
(Niklitschek 2001). Based on distributional evidence, older juvenile and adult shortnose
sturgeon are limited to oligohaline and low mesohaline regions of estuaries (<15 ppt), while by
their second year of life, Atlantic sturgeon fully tolerate salinities ranging from 0 to 35 ppt
(Dovel and Berggen 1983; Dovel et al. 1992; Kieffer and Kynard 1993; Colligan et al. 1998).
Jenkins et al. (1993) exposed shortnose sturgeon young-of-the-year (age 22-330 days) to
acute transitions in salinity for periods of 18-96 hr. Larvae (22 d ays old) showed >50 percent
mortality at 9 ppt exposure for 48 hours. Juveniles (63 days [48 hr] and 76 days old[96 hr])
27
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Shortnose Sturgeon Caught Between June 1 and September 30
Maryland
w
Legend
e Shortnose Sturgeon Capture Sites
•k State and U.S. Capitals
I I Chesapeake Bay Watershed
Figure 3. Map of all U. S. Fish and Wildlife Service sturgeon capture location stations
where shortnose sturgeon were caught from June 1-September 30, 1999-March 2003.
Sources: Mangold 2003, Spells 2003, Skeveland et al. 2000.
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All Shortnose Sturgeon Caught Between 1994 and March 2003
Figure 4. Map of all U.S. Fish and Wildlife Service sturgeon capture location stations where
shortnose sturgeon were caught year-round between 1994-March 2003.
Sources: Mangold 2003, Spells 2003, Skjeveland et al. 2000.
29
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showed reduced survival (-60 percent) at 13-15 ppt. At 96 hours exposure, 76 days old
juveniles experienced complete mortality at 15 ppt. Yearlings (330 days old) exposed to 25 ppt
showed 100 percent survival during an 18 hr trial, but were extremely stressed and probably
would have succumbed past the experiment's end (Jenkins et al. 1993). No yearlings survived
acute exposures to 30 or 35 ppt.
Niklitschek (2001), in dissertation research, exposed shortnose sturgeon juveniles (-6-12
months in age) to salinity conditions after more gradual periods of acclimation (1 ppt/day). In 10
day trials at 0 to 22 ppt, he observed comparatively lower growth and higher routine metabolism
rates for shortnose sturgeon than Atlantic sturgeon. In spatially explicit habitat models, these
bioenergetic differences contributed to habitat curtailments in lower tributaries and the mainstem
of the Chesapeake Bay due to high salinity effects there. Salinity was predicted to be a chief
factor contributing to lower (often negative) production of shortnose sturgeon in lower
Chesapeake Bay habitats in comparison to tidal fresh habitats (<0.5 ppt) in the upper Chesapeake
Bay and major tidal tributaries (e.g., Potomac, Rappahannock, James, and Nanticoke Rivers. In
behavioral studies (Niklitschek 2001), juvenile shortnose sturgeon (as well as Atlantic sturgeon)
did not discriminate between salinities of 0 and 8 ppt, nor did they exhibit preference between 8
and 15 ppt. Juvenile shortnose sturgeon showed a stressed behavioral response and reduced
survival at 29 ppt in comparison to salinities 0, 8, 15, and 22 ppt.
Distribution Studies
Distribution studies and laboratory experiments support the view that shortnose sturgeon
show preference for riverine and estuarine habitats over marine ones (e.g., Secor 2003).
Shortnose adults have been reported occasionally in coastal waters up to 31 ppt, but typically
occur within several kilometers of their natal estuaries (Dadswell et al. 1984; Kynard 1997). As
an example, shortnose sturgeons recorded in Sandy Hook Bay are believed to be part of Hudson
River population (Dadswell et al. 1984). Kynard (1997) described the life cycle of shortnose
sturgeon as freshwater amphidromous, which specifies freshwater as spawning location but
occasional forays into estuaries and coastal regions that are unrelated to spawning. This
contrasts with the sympatric Atlantic sturgeon, which are considered true anadromous fishes that
must migrate into coastal waters to complete their life cycles (Kynard 1997; Dovel and Berggren
1983; Dovel et al. 1992). Freshwater amphidromy has also been termed semi-anadromy, which
also typifies the life cycle of Chesapeake Bay white perch.
The life cycle for shortnose sturgeon in regions north of South Carolina has been
generalized by several authors (Dadswell et al. 1984; Bain 1997; Kynard 1997).
1. Adults move from brackish wintering grounds to head of estuary for spawning;
2. Adults feed in freshwater tidal portion during summer months and move back down
estuary for winter; and
3. Juveniles disperse from tidal freshwater (where they originated) to brackish winter
grounds during their first year of life.
In general, shortnose sturgeon do not invade salinities greater than 15 ppt, with centers of
concentrations at less than 5 ppt for all life history stages during summer months (Dadswell et al.
30
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1984; Brundage and Meadows 1982; Dovel et al. 1992; Geogehan et al. 1992; Collins and Smith
1996; Bain 1997; Haley 1999). There are at least two 'landlocked' populations of shortnose
sturgeon that can complete their life cycles in freshwater - the Santee Cooper and Holyoke Pool
sub-populations (Kynard 1997).
Kynard (1997) hypothesized that there occurred latitudinal trends in the propensity of
individuals of a population to move outside the natal estuary into coastal waters. Fish from the
most northerly populations (St. John River, New Brunswick) would emigrate into coastal regions
during winter months to avoid stressful temperatures. Shortnose from systems between
Merrimack River and Delaware Bay were the least likely to migrate to coastal waters since
temperature conditions were favorable in these estuaries year-round. In systems from South
Carolina to Florida (St. Johns Estuary), summer temperatures may drive shortnose adults to use
down-estuary and coastal areas.
The issue of coastal occurrence of shortnose remains controversial. Past studies have
misidentified Atlantic sturgeon juveniles as shortnose sturgeon (Kynard 1997). Physiological
salinity limits on adult shortnose sturgeon are not fully understood at this time. Genetic
evidence strongly indicates limited straying among natal estuaries (Wirgin et al. in press).
Indeed, Kynard (1997) concludes, "The lack of marine movements by most adults suggests that
the recolonization rate of shortnose.. .would be slow." Still, some records of shortnose in coastal
waters (up to 31 ppt; Dadswell 1984) cannot be questioned. An interesting case in point is the
recent 'invasion' of hatchery shortnose sturgeon stocked into the Savanna River yet recaptured
in lower South Carolina estuaries (Smith et al. 2002). Clearly these fish must have left Savanna
River and emigrated into waters that approached marine salinities in the inter-coastal waterway.
Chesapeake Bay Salinity Distributions
Maps of long-term averaged bottom salinity distributions document a lack of overlap of
the preferred (<5 ppt) and a limited overlap with the likely upper salinity tolerance (<15 ppt) of
shortnose sturgeon and deep-water and deep-channel designated use habitats during the summer
months (figures 5, 6 and 7, respectively).
31
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Salinity
<5 ppt
>5 ppt
Figure 5. Map of summer averaged bottom water salinities <5 ppt based on
Chesapeake Bay Water Quality Monitoring Program data from 1996-2000.
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Figure 6. Map of summer averaged bottom water salinities <15 ppt based on
Chesapeake Bay Water Quality Monitoring Program data from 1996-2000.
33
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Deep Water Habitat Designated Use
Maryland
Legend
E Cfeep Water Habitat
State and U.S. Capitals
I I Che sa peake Bay Watershed
¦!- > t t- J-
I 1 I In*
Figure 7. Long-term averaged spatial distribution of deep-water designated use habitats for
comparison only with figures 5 and 6 salinity distributions. Actual deep-water designated use
habitats will be determined based on month by month delineation of the pycnocline depths
using Chesapeake Bay water quality monitoring cruise data.
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Life History of Shortnose Sturgeon
Shortnose sturgeon are benthic fish that feed on a variety of benthic and epibenthic
invertebrates including molluscs, crustaceans (amphipods, chironomids, isopods), and
oligochaete worms (Vladykov and Greeley 1963; Dadswell 1979). Shortnose sturgeon are long-
lived (30 years) and, particularly in the northern extent of their range, mature at late ages. In the
north, males reach maturity at 5 to 10 years, while females mature between 7 and 13 years.
In the northern extent of their range, shortnose sturgeon exhibit three distinct movement
patterns. These migratory movements are associated with spawning, feeding, and overwintering
activities. In spring, as water temperatures rise above 8°C, pre-spawning shortnose sturgeon
move from overwintering grounds to spawning areas. Spawning occurs from mid/late March to
mid/late May depending upon location. In populations that have free access to the total length of
a river (e.g., no dams within the species' range in a river: Saint John, Kennebec, Altamaha,
Savannah, Delaware, and Merrimack Rivers), spawning areas are located at the farthest
accessible upstream reach of the river, often just below the fall line (NOAA National Marine
Fisheries Service 1998a). Shortnose sturgeon spawn in upper, freshwater sections of rivers and
feed and overwinter in both fresh and saline habitats. Shortnose sturgeon are believed to spawn
at discrete sites within the river (Kieffer and Kynard 1996).
Adult shortnose sturgeon typically leave the spawning grounds soon after spawning.
Non-spawning movements include rapid, directed post-spawning movements to downstream
feeding areas in spring and localized, wandering movements in summer and winter (Dadswell et
al. 1984; Buckley and Kynard 1985; O'Herron et al. 1993). Kieffer and Kynard (1993) reported
that post-spawning migrations were correlated with increasing spring water temperature and
river discharge. Young-of-the-year shortnose sturgeon are believed to move downstream after
hatching but remain within freshwater habitats (Dovel 1981). Older juveniles tend to move
downstream in fall and winter as water temperatures decline and the salt wedge recedes.
Juveniles move upstream in spring and feed mostly in freshwater reaches during summer.
Shortnose sturgeon occur at depths between 1 and 12 meters (Kieffer and Kynard 1993;
Savoy and Shake 2000: Welsh et al. 2000).
Status of Shortnose Sturgeon in the Chesapeake Bay
In the final recovery plan, the NOAA National Marine Fisheries Service identified 19
separate distinct populations occurring in New Brunswick Canada (1); Maine (2); Massachusetts
(1); Connecticut (1); New York (1); New Jersey/Delaware (1); Maryland and Virginia (1); North
Carolina (1); South Carolina (4); Georgia (4); and Florida (2) (NOAA National Marine Fisheries
Service 1998a). The NOAA National Marine Fisheries Service stated that loss of a single
shortnose sturgeon population segment may risk the permanent loss of unique genetic
information that is critical to the survival and recovery of the species and that, therefore, each
shortnose sturgeon population should be managed as a distinct population segment or recovery
unit for the purposes of Section 7 of the Endangered Species Act (NOAA National Marine
Fisheries Service 1998a). The NOAA National Marine Fisheries Service concluded in the
Biological Opinion for the Washington Aqueduct Permit that because of this policy, actions that
could adversely affect a DPS or recovery unit would be evaluated in terms of their potential to
jeopardize the continued existence of an individual population segment (as opposed to the
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existence of shortnose sturgeon range-wide) (NOAA National Marine Fisheries Service 2002).
The NOAA National Marine Fisheries Service recovery plan indicates that shortnose
sturgeon found in the Chesapeake Bay and its tributaries are considered part of the Chesapeake
Bay distinct population segment. Welsh et al. (1999) summarizes historical and recent evidence
of shortnose sturgeon presence in the Chesapeake Bay. The first published account of shortnose
sturgeon in the Chesapeake system was an 1876 record from the Potomac River reported in a
general list of fishes of Maryland (Uhler and Lugger 1876). Other historical records of
shortnose sturgeon in the Chesapeake Bay as reviewed by Dadswell et. al. (1984) are not
conclusive, as most likely these species were misidentified Atlantic sturgeon and possibly mis-
identified tributaries as well (D. Secor, personal communication, 2003).
Delaware/Chesapeake Migratory Corridor
The issue of whether shortnose sturgeon naturally populates the Chesapeake Bay through
local reproduction or immigration centers on the role of C&D Canal as a migration corridor. The
Delaware population has long been noted for having a viable and moderately large shortnose
sturgeon population. Brundage and Meadows (1982) reviewed all literature and reports for the
period 1817-1979 and concluded that the center of distribution of adults during summer months
was 1-3 ppt. For the more recent period 1973-1979, a small concentration of shortnose sturgeon
was observed in proximity to the C&D Canal, prompting them to conclude that "...interchange
between the two estuaries [Delaware and Chesapeake] would seem highly probable." Hastings
et al. (1987), estimated a moderately large population (in comparison to Hudson River and St.
John River Canada) of 6,000-14,000 sturgeons in the upper tidal estuary for the period 1981-
1987. Several authors have speculated that the range of the Delaware population was probably
contracted during much of 20th Century due to an anoxic/hypoxic zone of water occurring
between Philadelphia and Wilmington (Brundage and Meadows 1982; Kynard 1997), but that
recent improvements in water quality may have contributed to a range expansion into areas
including the vicinity of C&D Canal. Kynard (1997) in particular, called attention to the
likelihood that the C&D Canal may in recent times (since improvement in water quality and
range expansion in the Delaware Bay) serve as a corridor for emigration by Delaware population
shortnose sturgeon into the Chesapeake Bay.
In contrast to the Delaware Bay, there is little evidence that shortnose sturgeon occur in
abundance in the Chesapeake Bay or in fact remain viable. In the early publication, Fishes of
Chesapeake Bay, Hildebrand and Schroeder (1927), called into question whether shortnose
sturgeon remained in the Chesapeake Bay and believed that the very rare observations of
shortnose sturgeon in the 20th Century may have been due to taxonomic misidentifications.
Modern ichthyologists continue to debate whether shortnose sturgeon historically occurred in
Chesapeake Bay tributaries, or whether their abundances approached those observed elsewhere
(J. Waldman, personal communication, 2003; J. Musick, personal communication, 2002).
It is unknown at this time whether there is a reproducing population of shortnose
sturgeon in the Chesapeake Bay. Kynard (1997) suggests that no reproducing populations of
shortnose sturgeon exist between the Delaware and Cape Fear estuaries, but may be related to
shared qualities of the Chesapeake Bay and North Carolina estuaries including shallow water
bathymetries (Paul 2001), large historical inputs of sediment and nutrients to these systems
36
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(Cooper 1995; Brush 2001; Secor and Austin, in review), and the low volume of suitable
spawning habitats (clean rubble, cobble and other substrate needed for egg attachment).
Dadswell et al. (1984) and Welsh et al. (2002) documented occurrence of shortnose
sturgeon in the Chesapeake Bay in the vicinity of C&D Canal for the periods 1976-1981 and
1996-2001, respectively. Both these periods contained a set of anomalously wet years
(http://md.water.usgs.gov/monthly/bay.html), which would be expected to favor emigration
through the canal by Delaware population sturgeons. Further, an unusually strong spring freshet
in 1996 altered salinity structure throughout most of the Chesapeake Bay for much of the spring
and summer. This would have facilitated dispersal of shortnose sturgeon to regions away from
the upper Chesapeake Bay (C&D Canal) and could account for recent occurrences in Potomac
River.
The Federal Recovery Plan for Shortnose sturgeon (NOAA National Marine Fisheries
Service 1998a) noted these post-1996 occurrences, and in a precautionary framework, used the
occurrence data as evidence for listing the Chesapeake Bay as a Distinct Population Segment.
Recent genetic data, however, indicates that shortnose sturgeons captured in the Chesapeake Bay
since 1996 represent a sub-set of the Delaware Bay's gene pool (Wirgin et al., in review). If the
Delaware population continues to expand in abundance and range, we should expect increased
emigration of shortnose sturgeon through the C&D Canal and into other parts of the Chesapeake
Bay, particularly in wet years.
Genetic Findings
Research conducted by the New York University School of Medicine involving
mitochondrial DNA (mtDNA) analysis of shortnose sturgeon populations suggests that shortnose
sturgeon captured in the upper Chesapeake Bay may have migrated from the Delaware River to
the upper Chesapeake through the Chesapeake and Delaware Canal (Grunwald et al. 2002). In
this study, genetic comparisons were made among all shortnose sturgeon populations for which
tissue samples were available. All population comparisons exhibited clear and significant
differences in haplotype frequencies except for comparisons between the Upper/Lower
Connecticut River and Delaware/Chesapeake. There were no unique haplotypes in the
Chesapeake Bay fish. Samples from four fish from the Potomac River were analyzed and results
indicate that these fish exhibited the same haplotypes as fish found elsewhere in the Chesapeake
Bay and in the Delaware River. These results suggest that some or all of the sturgeon captured
in the Chesapeake Bay and its tributaries may not be part of the Chesapeake Bay, but rather
transients from the Delaware population.
However, the Washington Aqueduct Permit biological opinion concluded that
mitochondrial DNA (mtDNA) represents only a fraction (less than 1 percent) of the genetic
material and is maternally inherited. Therefore, in order to obtain conclusive results, it is
necessary to look at nuclear DNA (nDNA), which represents greater than 99 percent of the
genetic material and is biparentally inherited (NOAA National Marine Fisheries Service 2002).
In the absence of stronger evidence to the contrary, the NOAA National Marine Fisheries
Service presumes that shortnose sturgeon captured in the Chesapeake Bay and its tributaries are
part of the Chesapeake Bay distinct population segment (NOAA National Marine Fisheries
Service 2002).
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Field Study Results
The U.S. Fish and Wildlife Service conducted a sampling study sponsored by the U.S.
Army Corps of Engineers between 1998 and 2000 in the Maryland waters of the Chesapeake
Bay to determine the occurrence of shortnose and Atlantic sturgeon in areas of proposed dredge-
fill operations (Skjeveland et. al. 2000). This study included fishing at a total of 24 sites within
the Chesapeake Bay, five of which were located in the middle Potomac River approximately 30
to 74 miles downstream of the Washington Aqueduct discharge site. During this study, no
shortnose sturgeon were captured in the Potomac or Susquehanna rivers. An additional study by
the U.S. Fish and Wildlife Service was performed in the Potomac River and included sampling
at two areas in the vicinity of Little Falls, Virginia, which are environments that are consistent
with the preferred spawning habitat of shortnose sturgeon and are located near the Aqueduct
discharge sites (Eyler et. al. 2000). No shortnose sturgeon were captured during this study
either.
A separate U.S. Fish and Wildlife Service sampling study was also conducted in the
upper Chesapeake Bay mainstem, lower Susquehanna River and Chesapeake/Delaware Canal
during 1998 and 2000 in conjunction with a Section 7 consultation for the Baltimore Harbor and
Channels Federal Navigation Project (as cited in NOAA National Marine Fisheries 2002). This
study involved bottom gillnetting at 19 sites within the upper Chesapeake Bay mainstem and
lower Susquehanna River, and tracking of sonically tagged sturgeon within the upper Bay and
the Canal. No shortnose sturgeon were captured at any of the 19 sites. Figure 8 illustrates the
gill netting sites from these three U.S. Fish and Wildlife Service studies where no sturgeon were
caught.
The U.S. Fish and Wildlife Service Atlantic Sturgeon Reward Program has documented
the incidental captures of 50 shortnose sturgeon from various locations in the Bay over the six
year duration of the program (Mangold 2003; Spells 2003; Skjeveland et. al. 2000) (see Figure
4). The majority of these fish were tagged and tissue samples were taken from 36 fish in order
to determine the genetic characteristics of the individuals. The shortnose sturgeon have been
incidentally captured via this program from the lower Susquehanna River (4), the Bohemia River
(2), Potomac River (6), south of the Bay Bridge near Kent Island (2), near Howell Point (1), just
north of Hoopers Island (1), the Elk River (1) and Fishing Bay (2). The remaining 31 shortnose
sturgeon were captured in the upper Bay north of Hart-Miller Island. These fish were captured
alive in either commercial gillnets, poundnets, fykenets, eel pots, hoop nets, or catfish traps.
According to the NOAA National Marine Fisheries Service Washington Aqueduct Permit
biological opinion, the U.S. Fish and Wildlife Service studies may not have been comprehensive
enough to determine the presence or absence of sturgeon in the upper tidal Potomac River
(NOAA National Marine Fisheries Service 2002). Sampling sites may have been too deep with
too strong a current and timing and duration of the sampling events and the type of nets
employed may not have been appropriate for targeting shortnose sturgeon (NOAA National
Marine Fisheries Service 2002). This finding was reported at the same time as documenting no
captures of shortnose sturgeon during a 2 year U.S. Fish and Wildlife Service bottom gill netting
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All Sturgeon Monitoring Locations Where There Were No Captures
Figure 8. Locations of all the U.S. Fish arid Wildlife Service fisheries-independent sturgeon
sampling stations where no sturgeon were caught.
Source: Skjeveland et al. 2000.
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study on the Potomac River which included a total of 4,590 fishing hours. Furthermore, it should
be noted that it is the opinion of the National Marine Fisheries Service that the U.S. Fish and
Wildlife Service studies should not be used as conclusive indicator of shortnose sturgeon
absence in the upper tidal Potomac River (NOAA National Marine Fisheries Service 2002).
A 2000 NOAA National Marine Fisheries Service report, entitled "A Protocol for Use of
Shortnose and Atlantic Sturgeons" identified a minimum sampling protocol for use in north
central rivers (Chesapeake drainages to the Merrimack River) to confirm shortnose sturgeon
presence or absence. The NOAA National Marine Fisheries Service Washington Aqueduct
Permit biological opinion indicated that the U.S. Fish and Wildlife Service studies did not follow
this desired protocol, which was published after the studies commenced. That report cited that
the U.S. Fish and Wildlife Service sampling sites may have been too deep, in areas with too
strong a current to adequately document the presence of shortnose sturgeon (NOAA National
Marine Fisheries Service 2002). In addition, the timing and duration of the sampling events and
the type of nets employed may not have been appropriate for targeting shortnose sturgeon habitat
in question (NOAA National Marine Fisheries Service 2002).
Lacking conclusive data, the NOAA National Marine Fisheries Service's Washington
Aqueduct Permit biological opinion assumed the presence of shortnose sturgeon based on the
documented presence of this species and suitable spawning habitat in the Potomac River system.
The NOAA biological opinion cited evidence from the life history attributes of shortnose
sturgeon which suggests that fish from the Chesapeake Bay distinct population segment were
also spawning in at least the Susquehanna, Gunpowder, and Rappahannock river systems
(NOAA National Marine Fisheries Service 2002).
Habitat Quality Benefits from Dissolved Oxygen Criteria Attainment
Recent adoption of new Chesapeake Bay basinwide caps on nitrogen, phosphorus and
sediment loads by all seven watershed jurisdictions-New York, Pennsylvania, Maryland,
Virginia, West Virginia, Delaware and the District of Columbia-and the EPA will result in
significant improvements in tidal water quality (U.S. Environmental Protection Agency 2003b).
Restoration of sturgeon habitat is among the many benefits that will be achieved. Open-water
designated use habitats currently unsuitable for sturgeon will be restored. Upon attainment of
the 175 million pounds total nitrogen loading cap (110 million pound reduction from 2000 loads)
and the 12.8 million pound total phosphorus loading cap (6.3 million pound reduction from 2000
loads), dissolved oxygen levels last observed in the 1950s and early 1960s will become the
norm. Bay shorelines will likely see over 185,000 acres of underwater bay grasses, more than
double the acreages mapped today.
The adoption of the new loading caps underscores the commitment of the Chesapeake
Bay watershed partners to restoring the Bay. These loading caps are the greatest, most
challenging and stringent that have ever been established. According to the Chesapeake Bay
Commission's The Cost of a Clean Bay, the jurisdictions will need an additional 12.8 billion
dollars to achieve these goals (Chesapeake Bay Commission 2003).
Attainment of these challenging yet feasible loading cap goals and the resultant restored
water quality conditions will mean a substantial improvement to the Bay. Nevertheless, the
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seasonal designated deep-water and deep-channel habitats in the mesohaline Chesapeake Bay
and lower rivers will still not be suitable for sturgeon during the summer months.
Recovery of the Shortnose Sturgeon
The Recovery Plan provides a strategy to protect shortnose sturgeon populations and
habitats. The recovery outline includes three shortnose sturgeon recovery objectives: 1.
Establishing Listing Criteria; 2. Protect Shortnose Sturgeon Population and Habitats; and 3.
Rehabilitate Habitats and Population Segments (NOAA National Marine Fisheries 1998a). In
addition to the Regional Criteria Guidance the Chesapeake Bay Program partners have been
initiating programs and policies throughout the Chesapeake Bay, which incorporate many of the
elements of the Rehabilitate Habitats and Population Segments recovery strategy. In fact, the
partners spend millions of dollars a year on the restoration of the Bay. The Chesapeake 20005
agreement outlines some of these commitments which improve habitat for the Bay and are
consistent with the Recovery Plan for the Shortnose Sturgeon. Some of these include:
Restoring fish passage for migratory fish to more than 1,357 miles of currently blocked
river habitat by 2003 and establishing monitoring program to assess outcomes;
Work with local governments, community groups and watershed organizations to
develop and implement locally supported watershed management plans in two-thirds of
the watershed to address the protection, conservation and restoration of stream corridors,
riparian forest buffers and wetlands for the purposes of improving habitat and water
quality;
Correct the nutrient- and sediment-related problems in the Chesapeake Bay and its tidal
tributaries sufficiently to remove the Bay and the tidal portions of its tributaries from the
list of impaired waters under the Clean Water Act (the Regional Criteria Guidance is
part of this commitment);
Through continual improvement of pollution prevention measures and other voluntary
means, strive for zero release of chemical contaminants from point sources, including air
sources to the Bay;
Ensure that measures are in place to meet our riparian forest buffer restoration goal of
2,010 miles by 2,010;
Assess the effects of airborne nitrogen compounds and chemical contaminants on the Bay
ecosystem and help establish reduction goals for these contaminants;
Establish appropriate areas within the Chesapeake Bay and its tributaries as 'no discharge
zones' for human waste from boats;
Strengthen programs for land acquisition and preservation within each state that are
supported by funding and target the most valued lands for protection;
Reduce the rate of harmful sprawl development of forest and agricultural land in the
Chesapeake Bay watershed by 30 percent;
Make education and outreach a priority in order to achieve public awareness and personal
involvement on behalf of the Bay and local watersheds.
5The entire Chesapeake 2000 agreement is available on the web at: www.chesapeakebav.net.
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Enhance funding for locally-based programs that pursue restoration and protection
projects that will assist in the achievements of the goals of this and past agreement;
FINDINGS
The EPA has determined through consultation with the U.S. Fish and Wildlife Service
and the NOAA National Marine Fisheries Service, that the only endangered or threatened
species under the NOAA Fisheries jurisdiction in the evaluation area that will potentially be
affected is the endangered shortnose sturgeon (Acipenser brevirostrum). All the other federal
listed species within the Chesapeake Bay and its tidal tributaries would either not be affected or
would be beneficially affected by the issuance of the Regional Criteria Guidance.
The EPA has determined that the recommended water clarity criteria will not likely
adversely effect the listed species evaluated in this document. Furthermore, the EPA has
determined that the proposed water clarity criteria will beneficially affect preferred habitat,
spawning areas and food sources that the listed shortnose sturgeon depends on.
The EPA has determined that the recommended chlorophyll a criteria will not likely
adversely affect the listed species evaluated in this document. Furthermore, the EPA has
determined that the recommended chlorophyll a criteria will beneficially affect preferred habitat,
spawning habitat and food sources that the listed species depends on.
The EPA has determined that the collective application of dissolved oxygen criteria for
the migratory fish spawning and nursery and open-water fish and shellfish designated uses are
fully protective of shortnose sturgeon survival and growth for all life stages.
The migratory spawning and nursery 6 mg liter"1 7-day mean and 5 mg liter"1
instantaneous minimum criteria will fully protect spawning shortnose sturgeon.
The February 1 through May 31 application period for the migratory spawning
and nursery criteria fully encompasses the mid-March through mid-May
spawning season documented previously from the scientific peer reviewed
literature.
The individual components of the open water criteria protect shortnose sturgeon
growth (5 mg liter"1 30-day mean), larval recruitment (4 mg liter"1 7-day mean)
and survival (3 .2 mg liter"1 instantaneous minimum). A 4.3 mg liter"1
instantaneous minimum criterion applies to open waters with temperatures above
29°C considered stressful to shortnose sturgeon.
The open water criteria applied to tidal fresh waters includes a 5.5 mg liter"' 30-
day mean criterion providing extra protection of shortnose sturgeon juveniles
inhabiting tidal freshwater habitats.
The EPA has determined that adoption of the proposed dissolved oxygen criteria into
Maryland, Virginia, Delaware and the District of Columbia's state water quality standards and
their eventual attainment will beneficially affect shortnose sturgeon spawning, nursery, juvenile
and adult habitats and food sources by driving widespread nutrient reduction loading actions
leading to increasing existing ambient dissolved oxygen concentrations. This determination is
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consistent with and pursuant to Endangered Species Act provisions that state that the EPA is to
use its authority to further the purpose of protecting threatened and endangered species (see 16
U.S.C. § 1536(a)). It is also consistent with the NOAA National Marine Fisheries Recovery
Plan (1998a) for shortnose sturgeon which recommends working cooperatively with states to
promote increased state activities to promote best management practices to reduce non-point
sources.
The EPA has determined that adoption, implementation and eventual full attainment of
the states adopted dissolved oxygen water quality standards will result in significant
improvements in dissolved oxygen concentration throughout the tidal waters to levels last
observed consistently over four to five decades ago in Chesapeake Bay and its tidal tributaries.
The EPA recognizes that dissolved oxygen criteria for June through September for the
deep-water seasonal fish and shellfish and the deep-channel designated use are at or below levels
that protect shortnose sturgeon. The EPA believes there are strong lines of evidence that
shortnose sturgeon historically have not used deep-water and deep-channel designated use
habitats during the summer months due to naturally pervasive low dissolved oxygen conditions.
Published findings in the scientific literature regarding salinity preferences (tidal
fresh to 5 ppt) and salinity tolerances (<15 ppt) clearly indicate shortnose
sturgeon habitats are unlikely to overlap with the higher salinity deep-water and
deep-channel designated use habitats.
The EPA has concluded, based on extensive published scientific findings and in-
depth analysis of the 1400 record U.S. Fish and Wildlife Service Reward Program
database, that these same deep-water and deep-channel regions have not served as
potential habitats for sturgeon during the June through September time period
when there is a natural tendency for low dissolved oxygen conditions to occur.
The EPA recognizes the potential limitations of the U.S. Fish and Wildlife
Service data set. However, the EPA believes the significant extent of the capture
records-400 stations and 1400 individuals caught-provides substantial evidence
for the lack of a potential conflict between shortnose habitat and seasonally
applied deep-water and deep-channel designated uses.
The EPA had determined that the recommended dissolved oxygen criteria for the refined
designated uses will not likely adversely effect the listed species evaluated in this document.
Furthermore, the EPA has determined that the Chesapeake Bay dissolved oxygen criteria will
beneficially affect critical habitat and food sources that the listed species is dependent on.
SUMMARY AND CONCLUSION
Shortnose sturgeon are endangered throughout their entire range (NOAA National
Marine Fisheries Service 2002). According to NOAA, in the Final Biological Opinion for the
Washington Aqueduct, this species exists as 19 separate distinct population segments that should
be managed as such; specifically, the extinction of a single shortnose sturgeon population risks
permanent loss of unique genetic information that is critical to the survival and recovery of the
43
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species (NOAA National Marine Fisheries Service 2002). The shortnose sturgeon residing in the
Chesapeake Bay and its tributaries form one of the 19 distinct population segments.
Adult shortnose sturgeon are present in the Chesapeake Bay based on the 50 captures via
the U.S. Fish and Wildlife Service Atlantic Sturgeon Reward Program. However, the presence
and abundance of all life stages within the evaluation area itself are unknown. Preliminary
published scientific evidence suggests that the shortnose sturgeon captured in the Chesapeake
Bay may be part of the Delaware distinct population segment using the C & D Canal as a
migratory passage. However, the NOAA National Marine Fisheries Service recommend more
studies utilizing nuclear DNA need to be conducted before this can be proven conclusively.
Section 9 of the Endangered Species Act and Federal regulations pursuant to section 4(d)
of the Endangered Species Act prohibit the take of endangered and threatened species,
respectively, without special exemption. 'Take' is defined as to harass, harm, pursue, hunt,
shoot, wound, kill, trap, capture or collect, or to attempt to engage in any such conduct. Harm is
further defined by NOAA National Marine Fisheries Service to include any act which actually
kills or injures fish or wildlife. Such an act may include significant habitat modification or
degradation that actually kills or injures fish or wildlife by significantly impairing essential
behavioral patterns including breeding, spawning, rearing, migrating, feeding, or sheltering.
Harass is defined by U.S. Fish and Wildlife Service as intentional or negligent actions that create
the likelihood of injury to listed species to such an extent as to significantly disrupt normal
behavior patterns which include, but are not limited to, breeding, feeding or sheltering.
Incidental take is defined as take that is incidental to, and not the purpose of, the carrying out of
an otherwise lawful activity.
The Shortnose Sturgeon Recovery Plan (NOAA National Marine Fisheries Service
1998a) further identifies habitat degradation or loss (resulting, for example, from dams, bridge
construction, channel dredging, and pollutant discharges) and mortality (resulting, for example,
from impingement on cooling water intake screens, dredging and incidental capture in other
fisheries) as principal threats to the species' survival. The recovery goal is identified as delisting
shortnose sturgeon populations throughout their range, and the recovery objective is to ensure
that a minimum population size is provided such that genetic diversity is maintained and
extinction is avoided.
Considering the nature of the proposed Regional Criteria Guidance, the effects of the
recommended criteria, and future cumulative effects in the evaluation area, the proposed
issuance of Regional Criteria Guidance is not likely to adversely affect the reproduction,
numbers, and distribution of the Chesapeake Bay distinct population segment in a way that
appreciably reduces their likelihood of survival and recovery in the wild. This contention is
based on the following: (1) the adoption of the recommended dissolved oxygen criteria into state
water quality standards and subsequent attainment upon achievement of the Chesapeake Bay
watershed's nutrient loading caps will provide for significant water quality improvements to the
tributaries to the Chesapeake Bay (such as the Susquehanna, Gunpowder, and Rappahannock
rivers) where the shortnose sturgeon would most likely spawn and spend their first year of life;
(2) the main channel of the Chesapeake Bay most likely experienced reductions in dissolved
oxygen before large-scale post-colonial land clearance took place, due to natural factors such as
44
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climate-driven variability in freshwater inflow; and (3) there is strong evidence that shortnose
sturgeon have historically not used deep-water and deep-channel designated use habitats during
the summer months due to naturally pervasive low dissolved oxygen conditions.
Based on the evaluation conducted in this document it is the EPA's conclusion that the
proposed issuance of the Regional Criteria Guidance would not adversely affect the continued
existence of the Chesapeake Bay DPS of shortnose sturgeon. No critical habitat has been
designated for this species, and therefore, none will be affected. In fact, the EPA believes state
adoption of the criteria into water quality standards will directly lead to increased levels of
suitable habitat for shortnose sturgeon.
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APPENDICES
Appendix A Ambient Water Quality Criteria for Dissolved Oxygen, Water Clarity and
Chlorophyll a for the Chesapeake Bay and Its Tidal Tributaries.
Appendix B Technical Support Document for the Identification of Chesapeake Bay
Designated Uses and Attainability.
Appendix C. List of Federally Endangered Species for Maryland, Virginia, Delaware and the
District of Columbia.
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APPENDIX C
Endangered Species in Maryland, Delaware, Virginia, and the District of Columbia.
Listings by State and Territory as of October 24, 2002
Notes:
Displays one record per listing entity.
Includes experimental populations and similarity of appearance species.
Pertains to the range of a species, not the listing status within a State/Territory.
Includes non-nesting sea turtles and whales in State/Territory coastal waters.
Includes species under the sole jurisdiction of the National Marine Fisheries Service.
Source : U.S. Fish and Wildlife website http://ecos.fws.gov/webpage/
Maryland - 26 listings
Animals - 19
Status Listing
E Bat, Indiana (Myotis sodalis)
E Darter, Maryland (Etheostoma sellare)
T Eagle, bald (lower 48 States) (Haliaeetus leucocephalus)
T Plover, piping (except Great Lakes watershed) (Charadrius melodus)
E Puma, eastern (Puma concolor couguar)
T Sea turtle, green (except where endangered) (Chelonia my das)
E Sea turtle, hawksbill (Eretmochelys imbricata)
E Sea turtle, Kemp's ridley (Lepidochelys kempii)
E Sea turtle, leatherback (Dermochelys coriacea)
T Sea turtle, loggerhead {Caretta caretta)
E Squirrel, Delmarva Peninsula fox (Sciurus niger cinereus)
E Sturgeon, shortnose (Acipenser brevirostrum)
T Tiger beetle, northeastern beach (Cicindela dorsalis dorsalis)
T Tiger beetle, Puritan (Cicindelapuritana)
T Turtle, bog (northern) (Clemmys muhlenbergii)
E Wedgemussel, dwarf (Alasmidonta heterodon)
E Whale, finback (Balaenopteraphysalus)
E Whale, humpback (Megaptera novaeangliae)
E Whale, right (Balaena glacialis)
Plants - 7
Status Listing
T Joint-vetch, sensitive (Aeschynomene virginica)
E Gerardia, sandplain (Agalinis acuta)
T Amaranth, seabeach (Amaranthuspumilus)
T Pink, swamp (Helonias bullata)
1
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E Dropwort, Canby's (Oxypolis canbyi)
E Harperella (Ptilimnium nodosum)
E Bulrush, Northeastern (Scirpus ancistrochaetus)
Virginia -70 listings
Animals - 56
Status Listing
E Bat, gray (Myotis grisescens)
E Bat, Indiana (Myotis sodalis)
E Bat, Virginia big-eared (Corynorhinus (=Plecotus) townsendii virginianus)
XN Bean, Cumberland (pearlymussel) AL; free-flowing reach of the Tennessee
River below the Wilson Dam, Colbert and Lauderdale Counties, AL (Villosa
trabalis)
E Bean, purple (Villosaperpurpurea)
E Blossom, green (pearlymussel) (Epioblasma torulosa gubernaculum)
T Chub, slender (Erimystax cahni)
T Chub, spotfin (Cyprinella monacha) - Entire
E Combshell, Cumberlandian {Epioblasma brevidens) - Entire Range; except where
listed as Experimental Populations
XN Combshell, Cumberlandian AL; free-flowing reach of the Tennessee River
below the Wilson Dam, Colbert and Lauderdale Counties, AL (Epioblasma
brevidens)
E Darter, duskytail (Etheostoma percnurum) - Entire Range
T Eagle, bald (Haliaeetus leucocephalus) - Lower 48 States
E Fanshell (Cyprogenia stegaria)
E Isopod (Lirceus usdagalun) - Lee County cave
T Isopod, Madison Cave (Antrolana lira)
E Logperch, Roanoke (Percina rex)
XN Madtom, yellowfin (Noturus flavipinnis) - Holston River, VA, TN
T Madtom, yellowfin (Noturus flavipinnis) - Except where XN
E Monkeyface, Appalachian (pearlymussel) (Quadrula sparsa)
E Monkeyface, Cumberland (pearlymussel) (Quadrula intermedia) - Entire Range;
except where listed as Experimental Populations
XN Monkeyface, Cumberland (pearlymussel) (Quadrula intermedia) AL; Free-
flowing reach of the Tennessee River below the Wilson Dam, Colbert and
Lauderdale Counties, AL
E Mucket, pink (pearlymussel) (Lampsilis abrupta)
E Mussel, oyster (Epioblasma capsaeformis)- Entire Range; except where listed as
Experimental Populations
XN Mussel, oyster (Epioblasma capsaeformis) AL; Free-flowing reach of the
Tennessee River below the Wilson Dam, Colbert and Lauderdale Counties, AL
E Pearlymussel, birdwing (Conradilla caelata) - Entire Range; except where listed
as Experimental Populations
2
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E
E
E
E
XN
E
E
XN
T
E
E
E
E
T
E
E
E
T
E
E
E
E
E
E
T
T(S/A)
E
E
E
E
E
Plants - 14
Status
T
T
E
Pearlymussel, cracking (Hemistena lata) - Entire Range; except where listed as
Experimental Populations
Pearlymussel, dromedary {Dromus dromas) - Entire Range; except where listed
as Experimental Populations
Pearlymussel, littlewing (Pegias fabula)
Pigtoe, finerayed (Fusconaia cuneolus) - Entire Range; except where listed as
Experimental Populations
Pigtoe, finerayed {Fusconaia cuneolus) AL; free-flowing reach of the Tennessee
River below the Wilson Dam, Colbert and Lauderdale Counties, AL
Pigtoe, rough (Pleurobema plenum)
Pigtoe, shiny Entire Range; Except where listed as experimental populations
(Fusconaiacor)
Pigtoe, shiny (Fusconaia cor) - AL; free-flowing reach of the Tennessee River
below the Wilson Dam, Colbert and Lauderdale Counties, AL
Plover, piping (Charadrius melodus) - Except Great Lakes watershed
Puma, eastern {Puma concolor couguar)
Rabbitsfoot, rough {Quadrula cylindrica strigillata)
Riffleshell, tan {Epioblasma jlorentina walkeri (E. walkeri))
Salamander, Shenandoah {Plethodon shenandoah)
Sea turtle, green {Chelonia mydas) - Except where endangered
Sea turtle, hawksbill {Eretmochelys imbricata)
Sea turtle, Kemp's ridley {Lepidochelys kempii)
Sea turtle, leatherback {Dermochelys coriacea)
Sea turtle, loggerhead {Caretta caretta)
Snail, Virginia fringed mountain (Polygyriscus virginianus)
Spinymussel, James {Pleurobema collina)
Squirrel, Delmarva Peninsula fox {Sciurus niger cinereus) - Except Sussex
County, Delaware
Squirrel, Virginia northern flying {Glaucomys sabrinus fuscus)
Sturgeon, shortnose {Acipenser brevirostrum)
Tern, roseate {Sterna dougallii dougallii) - Northeast U.S. nesting population
Tiger beetle, northeastern beach {Cicindela dorsalis dorsalis)
Turtle, bog (Muhlenberg) (southern) {Clemmys muhlenbergii)
Wedgemussel, dwarf {Alasmidonta heterodon)
Whale, finback {Balaenopteraphysalus)
Whale, humpback {Megaptera novaeangliae)
Whale, right {Balaena glacialis [incl. Australis])
Woodpecker, red-cockaded (Picoides borealis)
Listing
Joint-vetch, sensitive {Aeschynomene virginica)
Amaranth, seabeach {Amaranthuspumilus)
Rock-cress, shale barren {Arabis serotina)
3
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T Birch, Virginia round-leaf (Betula uber)
E Bittercress, small-anthered (Cardamine micranthera)
E Coneflower, smooth (Echinacea laevigata)
T Sneezeweed, Virginia (Helenium virginicum)
T Pink, swamp (Helonias bullata)
E Mallow, Peter's Mountain (Iliamna corei)
T Pogonia, small whorled (Isotria medeoloides)
T Orchid, eastern prairie fringed (Platanthera leucophaea)
E Sumac, Michaux's (Rhus michauxii)
E Bulrush, Northeastern (Scirpus ancistrochaetus)
T Spiraea, Virginia (Spiraea virginiana)
District of Columbia - 3 listings
Animals - 3
Status Listing
E Amphipod, Hay's Spring (Stygobromus hayi)
T Eagle, bald (lower 48 States) (Haliaeetus leucocephalus)
E Puma, eastern (Puma concolor couguaf)
Plants - 0
Delaware - 19 listings
Animals - 15
Status Listing
T Eagle, bald (Haliaeetus leucocephalus) - Lower 48 States
T Plover, piping (Charadrius melodus)
E Puma, eastern (Puma concolor couguaf)
T Sea turtle, green (Chelonia mydas) - Except where endangered
E Sea turtle, hawksbill (Eretmochelys imbricata)
E Sea turtle, Kemp's ridley (Lepidochelys kempii)
E Sea turtle, leatherback (Dermochelys coriacea)
T Sea turtle, loggerhead (Caretta caretta)
E Squirrel, Delmarva Peninsula fox (Sciurus niger cinereus) - except Sussex
County, Delaware
XN Squirrel, Delmarva Peninsula fox [XN] (Sciurus niger cinereus)
E Sturgeon, shortnose (Acipenser brevirostrum)
T Turtle, bog (northern) (Clemmys muhlenbergii)
E Whale, finback (Balaenopteraphysalus)
E Whale, humpback (Megaptera novaeangliae)
E Whale, right (Balaena glacialis)
4
-------
Listing
Pink, swamp (Helonias bullata)
Pogonia, small whorled (Isotria medeoloides)
Dropwort, Canby's (Oxypolis canbyi)
Beaked-rush, Knieskern's (Rhynchospora knieskernii)
Sea turtle, green (Chelonia mydas) - Except where endangered
Sea turtle, hawksbill (Eretmochelys imbricata)
Sea turtle, Kemp's ridley (Lepidochelys kempii)
Sea turtle, leatherback (Dermochelys coriacea)
Sea turtle, loggerhead (Caretta caretta)
Whale, finback (Balaenopteraphysalus)
Whale, humpback (Megaptera novaeangliae)
Whale, right (Balaena glacialis)
Sturgeon, shortnose (Acipenser brevirostrum)
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