903R90103
CBP/TRS 40/90
April 1990
Ichthyoplankton Monitoring
and Research on the
Chesapeake Bay
Proceedings of a Consensus Workshop
U.S. Environmental Protection Agency
Region 111 Information Resource
Csuter (3PM52)
841 Chestnut Street
Philadelphia, PA 19107
TD
225
.C54
123
copy 2
Chesapeake
Bay
Program
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H.'^
d 11 •
Ichthyoplankton Monitoring
and Research on the
Chesapeake Bay
U.S. £ti\iiton.nerttal Protection Agency
Kf;L;on ill information Resource
Center (2PM52)
841 Chestnut Street
Philadelphia, PA 19107
Proceedings of a Consensus Workshop
December 5,1989
Baltimore, Maryland
April 1990
Printed by the United States Environmental Protection Agency
for the
Chesapeake Bay Program
Printed on recycled paper
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CONTENTS
Page
SUMMARY 1
INTRODUCTION 2
Organization of the Workshop 3
RECOMMENDATIONS 4
Monitoring 4
Research 7
REFERENCES 10
APPENDICES 11
Appendix A. Workshop Proposal 11
Appendix B. List of Participants 14
Appendix C. List of Issues and Topics 15
Appendix D. List of Questions 16
Appendix E. Workshop Agenda 17
Appendix F. Work Groups 18
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SUMMARY
Ichthyoplankton monitoring and research were discussed as a means to 1)
assess fish resources, 2) detect trends in abundance, 3) link trends to water
quality or habitat criteria, and 4) gain understanding of early life dynamics
that can be related to recruitment variability. Long-term ichthyoplankton
monitoring carried out on appropriate temporal-spatial scales, may be used to
estimate adult spawning biomasses, to define spawning seasons and areas, and
reveal trends that may occur over time as a result of changes in spawning
behavior or habitat alteration. Although monitoring may not identify
mechanisms causing changes in abundance, especially if the causes are complex
species interactions or fishing, it is can relate spawning occurrence, distri-
bution and intensity to water quality and habitat criteria.
In the context of the Chesapeake Bay Monitoring Program, few species
could be surveyed effectively by ichthyoplankton monitoring. Bay anchovy,
naked goby, and possibly hogchoker, are widely distributed, have protracted
spawning seasons, and are potentially abundant enough to be assessed by
present plankton monitoring efforts. Anadromous fishes cannot be monitored
effectively under the present schedule and effort. Routine monitoring is
unlikely to provide useful information about recruitment variability and
should not be carried out specifically for this purpose. Selected, archived
Bay Program plankton samples should be analyzed to evaluate the present
monitoring plan's ability to obtain ichthyoplankton data. This effort should
be undertaken before deciding to include ichthyoplankton in the Bay Monitoring
Program.
Research, including modeling, that is based on testable hypotheses and
which focuses on understanding mechanisms that affect mortality and growth
during early life is valuable to investigate early life dynamics and recruit-
ment variability, especially if coordinated with studies on older life stages
and environmental factors. Research should be carried out at appropriate
temporal-spatial scales. Each proposed project must stand on its own merit
and alternative approaches should be considered.
Alternative approaches sometimes may be more effective and less costly
than ichthyoplankton monitoring or research to achieve similar objectives.
For example, juvenile abundance surveys and other fishery-independent surveys,
when supplemented with analyses of stock dynamics, are valuable components of
a fishery management program. Some fishery-dependent approaches, such as
virtual population analysis, provide a posteriori estimates of abundance and
recruitment variability when age-specific catches are available. Alternative
approaches often do not provide estimates of initial egg numbers, early life
survival rates, or specific environmental conditions in early life when
highest mortality occurs. The alternative approaches may provide information
immediately useful for fishery management while process-oriented ichthyoplank-
ton research is important to shape long-term management strategies in the
Chesapeake Bay.
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INTRODUCTION
Objectives of the 1987 Chesapeake Bay Agreement include protection,
restoration, and enhancement of living resources in the Bay. Subcommittees on
Living Resources and on Monitoring have been charged to develop and implement
the means to attain goals and achieve objectives (Chesapeake Executive
Council, 1988a) . In this regard, an extensive Baywide monitoring program has
been underway for several years to collect long-term data on habitat, water
quality and living resources (Magnien 1987; Heasly e_t aQ. 1989). With respect
to fisheries, although stock assessments and fishery management plans for some
exploited species are included in the Bay Program activities (Chesapeake
Executive Council 1988b, 1988c), ichthyoplankton monitoring is not included.
The Workshop was held to discuss possible benefits of ichthyoplankton moni-
toring and, more generally, the role of research on fish early life stages in
assessing Chesapeake Bay fish resources.
The fluctuations in recruitment and abundance of fish stocks are caused
primarily by variable survival during the early life stages and by the
intensity of fishing on the recruited stock. A full understanding of the
mechanisms, processes and interactions that cause extreme fluctuations, and
sometimes declines, in abundance can only be achieved through long-term
research and management of fish resources (Houde 1987). A National Research
Council evaluation of the Chesapeake Bay Monitoring Program (National Research
Council 1988), while generally laudatory, criticized the Program for its
apparent lack of emphasis on living resources (i.e. fish stocks). Discussions
in the workshop focused on the possible benefits of ichthyoplankton monitoring
to understand effects of water quality, plankton abundances, and environmental
variability on fish spawning. The more difficult problem of determining
whether ichthyoplankton research can lead to an understanding of recruitment
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variability and its causes also was discussed, keeping in mind that alterna-
tive approaches, which do not depend upon ichthyoplankton sampling, might be
more appropriate in some instances to achieve the objective.
Organization of_ the Workshop
The Workshop was convened at the request of the Chesapeake Bay Living
Resources Subcommittee. Preliminary discussions between Dr. Michael
Hirshfield (Maryland DNR) and Dr. Edward Houde (University of Maryland,
Chesapeake Biological Laboratory) resulted in a workshop proposal being
submitted to Maryland DNR by the University's Center for Environmental and
Estuarine Studies (Appendix A). Twenty-two participants, including eight
invited experts (Appendix B), attended the workshop, which was held on
5 December 1989 in Baltimore, Maryland. Dr. Houde was the convener of the
Workshop. He and Dr. Hirshfield had developed a list of issues and topics
(Appendix C), and a list of questions (Appendix D) to be addressed in the
workshop.
The agenda (Appendix E) included a leadoff plenary session in the morning
that provided participants with background information on Chesapeake Bay
fisheries, past and ongoing ichthyoplankton monitoring/research, fishery-
independent stock assessment activities and an overview of the Chesapeake Bay
Monitoring Program. Invited experts provided information and discussed their
experiences on early life studies or stock assessments on other life stages.
Three working groups (Appendix F) met separately in the afternoon to discuss
and develop recommendations in three general areas:
0 Group I. Reproductive Success, Spawning Areas and Times, Environmental and
Habitat Criteria.
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0 Group II. Egg Production and Spawner Biomass Estimates, Trends in Species
Abundances, Indices of Community Structure.
0 Group III. Causes of Mortality, Early Life Stage Dynamics and Recruitment
Predictions.
A summary of discussions and recommendations by each Group was presented
in a closing plenary session. Consensus views and alternative approaches are
stressed in the report.
RECOMMENDATIONS
Recommendations are made under two subheadings, Monitoring and Research.
Participants recognized that these two activities are not always distinct or
easily separated. Long time series, if derived from data collected at
appropriate time and space scales, can be used to develop hypotheses, under-
take modeling, and carry out analyses on effects of environmental variables.
An important question faced by the workshop was whether ichthyoplankton
monitoring could be carried out successfully in the context of the present
Chesapeake Bay Monitoring Program.
Monitoring
Monitoring of_ fish eggs and larvae for species that are abundant, widely
distributed, and have a protracted spawning season may provide useful informa-
tion in the context of_ present Chesapeake Bay monitoring efforts. Because
Baywide monitoring is scheduled only once each 20 days at a relatively few
stations, spawning areas and times are not sampled accurately or precisely for
most Bay species. Exceptions may include the bay anchovy Anchoa mitchilli,
the naked goby, Gobiosoma bosci, and hogchoker, Trinectes maculatus. Corre-
lative information on eggs and small larvae of these species that links
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abundances with water quality, environmental parameters and other plankton
organisms could be used to examine long-term trends in abundance, timing of
spawning and shifts in spawning areas. Observed changes in abundance, based
solely on ichthyoplankton but without knowledge of adult abundances, may
attribute such changes to water quality or environmental factors when preda-
tor-prey relationships or effects of fishing actually were the primary causes.
Accordingly, care must be taken in interpreting abundance changes that could
be detected by ichthyoplankton monitoring.
The species that are good candidates for monitoring in the Chesapeake Bay
Program are small, unexploited by man, and often not surveyed in fishery-
independent stock assessments. Their eggs (anchovy and hogchoker) and small
larvae (all three species) are vulnerable to standard plankton sampling gears
and can be sampled effectively. Ichthyoplankton of selected species may be
one of a suite of indicators in a monitoring program. Long-term surveys of
ichthyoplankton may provide an index of^ trends In spawning biomass, although
accuracy and precision are not likely to be high because of the temporal/
spatial compromises incorporated into the Baywide monitoring plan. Ichthyo-
plankton, along with other plankton organisms, can bj? used to monitor the
forage base available to pelagic consumers and max serve a role in delineating
habitat quality or trends ijn eutrophication, although the relative scarcity of
fish eggs and larvae in the plankton lowers their value in this context as
accurate o_r precise indicators, compared U> more abundant plankton organisms.
The present monitoring schedule and efforts in the Bay are not adequate
to survey the spawning areas and times of anadromous fishes. If anadromous
ichthyoplankton were to be monitored in the Bay Program, intensive sampling
must b- Urected to specific areas and concentrated in the April-May time
period when these species spawn. However, it is not certain that the benefits
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to fishery management of such an approach would be greater than those derived
from abundance monitoring of other life stages. It was clear to most partici-
pants that, if monitoring of anadromous ichthyoplankton were carried out at
appropriate time and space scales, egg production and spawner biomass
estimates could be derived. Because egg production is an index of adult stock,
it can be used as a measure of management success. It was recognized that
intensive monitoring of anadromous ichthyoplankton in selected spawning areas
might define the environmental conditions that led to eventual juvenile year-
class abundances that are assessed by seine surveys in Maryland and Virginia
tributaries.
In some marine ecosystems, fish species diversity and fish community
structure can be determined via ichthyoplankton monitoring. But, this
approach cannot be used in the Chesapeake Bay where many valuable species are
recruited as juveniles from spawning that occurred in the ocean (e.g.
menhaden, spot, croaker, bluefish).
Ichthyoplankton monitoring by. itself should not be expected to contribute
significantly to recruitment predictions for Chesapeake Bay fish stocks.
Process-oriented research may serve such a role but routine monitoring will
not serve that purpose.
Alternatives to ichthyoplankton monitoring that accomplish similar
objectives include both fishery-dependent and independent approaches. Virtual
Population Analysis on exploited species for which age-specific catch data are
available can provide age-specific abundance estimates, including numbers of
recruits. The VPA analysis cannot provide a recruitment estimate until a
year-class has been fished for two or more years and also is not effective for
short-lived species or those not subject to exploitation. Young-of-the-year
indices (e.g. striped bass juvenile seine survey) can monitor prerecruit abun-
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dances at a life stage when relative abundance of the current year-class is
fixed. Trawling surveys or other fishery-independent surveys of juveniles and
adults can monitor trends in abundance of many fish stocks. The alternative
methods may not succeed in linking abundances at the life stage being
monitored to habitat criteria or environmental influences experienced during
the egg and larvae stages, especially if juvenile and adult habitat differs
from that of eggs and larvae.
It^ was the consensus o£ workshop participants that selected, archived
plankton samples from the Bay Monitoring Program be examined and analyzed for
ichthyoplankton tc> determine if^ the sampling design ijs adequate tc> evaluate
abundances and spatio-temporal distributions of selected species. The quality
of data, including precision of abundance estimates for candidate species
(e.g. bay anchovy, naked goby, hogchoker, perhaps a few others) needs to be
determined. Results of this proposed evaluation should be incorporated into
any decision on whether to include ichthyoplankton in future monitoring
activities. The preliminary evaluation also should estimate the costs of
removing, identifying and measuring ichthyoplankton, as well as analyzing
data.
Research
The consensus of the workshop was that ichthyoplankton research has a
role in studies o£ the Chesapeake Bay ecosystem and in fisheries management.
However, there was no blanket endorsement for such studies. Proposed research
projects on early life stages o|_ fishes must stand on their ovn merits and be
considered on a project-by-project basis. Ichthyoplankton research alone
generally is not sufficient to assess fish stocks or provide the information
on stock dynamics that is needed to manage populations. However, process-
oriented studies on ichthyoplankton were recommended, in which functions and
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mechanisms are studied that affect growth, mortality, and production of early
life stages. This type of research can tie early life population dynamics to
dynamics of older life stages. It serves a purpose in predicting recruitment
or developing models to do so, particularly in defining effects of the
environment, including contaminants, on survival of early life stages.
Participants emphasized that ichthyoplankton research should be based on
testable hypotheses that potentially can be falsified. Process-oriented
studies generally should be species-specific and must be carried out at_ appro-
priate time and space scales. Community-level studies may be feasible under
certain circumstances (e.g. anadromous species complex) to provide information
on mechanisms that influence the recruitment process. When possible, early
life history research and modeling should bjj linked vith studies on spawning
stock dynamics and environmental influences. Both long and short-term
research may have roles but the focus should be on processes and mechanisms.
Workshop participants recognized that long-term monitoring studies that depend
entirely on correlations to interpret environmental or stock-dependent
effects, while potentially misleading on their own, may have value in model
development and research program design.
The Chesapeake Bay Monitoring Program is accumulating data on the Bay and
its tributaries that can be supportive of ichthyoplankton research. Data on
hydrography, water quality, river flows, sediments and biological characteri-
zations are available. At present much of this data is being collected on
time and space scales that are inappropriate for early life studies of
anadromous species, but supportive data may have value in recruitment-process
research on forage species such as bay anchovy or naked goby.
Workshop participants recognized that alternative approaches sometimes
may be more effective and less costly than ichthyoplankton research in
8
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providing knowledge of_ fish stock dynamics, assessment and recruitment.
Young-of-the-year (i.e. juvenile) surveys on anadromous species are extremely
valuable to predict future year-class strengths, and through birth-date
analysis can provide some knowledge of environmental conditions encountered by
survivors during the earliest life stages. Birth-date analyses are not
a complete alternative method of recruitment analysis but are a
useful component of such analyses. For species that enter the Bay as juve-
niles (e.g. menhaden, some sciaenids), egg and larval studies within the Bay
are not possible, while assessments on juvenile stages may be quite effective
in determining stock dynamics of these fishes once they are recruited.
Although juvenile assessments, and models based upon these life stages,
provide important information on the dynamics of the stocks and year-class
strength, they examine only the survivors of the recruitment process. Thus,
they do not give estimates of initial numbers of eggs or larvae and their
survival rates. Consequently, they provide only limited knowledge of the
specific environmental effects and habitat conditions encountered by eggs and
larvae. The alternative approaches often do provide immediate information to
guide fishery management. Process-oriented ichthyoplankton research can
reveal mechanisms that influence early life dynamics and, as such, has a role
in development of. long-term management strategies in the Chesapeake Bay.
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REFERENCES
Chesapeake Executive Council. 1988a. Living resources monitoring plan.
Ches. Exec. Council, Chesapeake Bay Program Agreement Commitment Report,
Annapolis, MD. 94 pp.
. 1988b. Schedule for
developing Baywide resource management strategies. Ches. Exec. Council,
Chesapeake Bay Program Agreement Commitment Report, Annapolis, MD. 25 pp.
. 1988c. Stock assessment
plan. Ches. Exec. Council, Chesapeake Bay Program Agreement Commitment
Report, Annapolis, MD. 66 pp.
Heasly, P., S. Pultz and R. Batiuk. 1989. Chesapeake Bay basin monitoring
program atlas. Vol. 1. Water quality and other physiochemical monitoring
programs. 411 pp. Vol. 2. Biological and living resource monitoring
programs. 733 pp. U.S. Environmental Protection Agency, Chesapeake Bay
Liaison Office, Annapolis, MD.
Houde, E.D. (ed.). 1987. Long-range research needs for Chesapeake Bay living
resources. Report of a Workshop sponsored by the Maryland Department of
Natural Resources with support from U.S. Department of Agriculture.
Technical Series TS61-87, Center for Environmental and Estuarine Studies,
University of Maryland.
Magnien, R.E. (ed.). 1987. Monitoring for management actions. Chesapeake
Bay water quality monitoring program — first biennial report. Office of
Environmental Programs, Maryland Department of Health and Mental Hygiene.
61 pp.
National Research Council. 1988. Marine environmental monitoring in
Chesapeake Bay. Marine Board, National Research Council, Washington,
D.C. 81 pp.
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APPENDIX A
The University of Maryland System
Center for Environmental & Estuarine Studies
Chesapeake Biological Laboratory
Solomons, MD 20688-0038
ICHTHYOPLANKTON MONITORING AND RESEARCH
ON THE CHESAPEAKE BAY:
A WORKSHOP
Proposal To
Maryland Department of Natural Resources
Tidewater Administration
Tawes State Office Building
580 Taylor Avenue
Annapolis, Maryland 21401
By.
Edward D. Houde, Professor
(301) 326-4281
Project Duration; 4 months
Requested Funding Period: 6 Nov. 1989 - 5 March 1990
Budget Request: $ 5,968
Kenneth R. Tenore, Head of Laboratory Thomas C. Malone, Acting Director
Chesapeake Biological Laboratory Center for Environmental and
Estuarine Studies
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A workshop to address ichthyoplankton monitoring and research in the
Chesapeake Bay is proposed, to be held at the Lord Baltimore Hotel in
Baltimore, Maryland on 5 December 1989. The Maryland Department of Natural
Resources has requested advice and recommendations on the need to monitor fish
early life stages in the Bay and its tributaries, and more generally on the
benefits of early-life-stage studies in- the context of environmental, water
quality and fisheries management concerns.
Specific questions and topics/issues to be discussed by workshop partici-
pants are attached (Appendix B). The listed questions and issues are not
exclusive. Experts have been invited to participate and to provide a critical
evaluation of the benefits and costs of ichthyoplankton/monitoring research.
Not all of the participants are ichthyoplankton researchers. Some in fact
have questioned the usefulness of ichthyoplankton monitoring and research as
tools to enhance management or to improve understanding of environmental
effects on fishery resources.
Eight participants will be invited. Most already have expressed a strong
interest in the proposed workshop in telephone or personal conversations.
They are:
G. Laurence - NMFS, Northeast Fisheries Center, Narragansett, R.I.
V. Crecco - Connecticut Department of Environmental Protection,
Waterford, CT
D. Hoss - NMFS, Southeast Fisheries Center, Beaufort, N.C.
P. Rago - U.S. Fish and Wildlife Service, Kearneysville, W.VA
J. Olney - Virginia Institute of Marine Science, Gloucester Point, VA
W. Smith - NMFS, Northeast Fisheries Center, Sandy Hook, N.J.
W. Richkus - VERSAR Corporation, Columbia, MD
E. Setzler-Hamilton - Center for Environmental & Estuarine Studies,
Chesapeake Biological Laboratory, Solomons, MD
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Additional participants from State of Maryland agencies and the
University of Maryland Center for Environmental and Estuarine Studies are
anticipated. The total number of workshop participants should not exceed 20.
It is proposed that the workshop be held in the Inner Harbor area,
Baltimore, at the Lord Baltimore Hotel. The one-day workshop will provide an
opportunity to discuss each issue and to make recommendations when possible.
Recommendations will be summarized in a workshop report, to be delivered in
draft form to Maryland DNR by 10 February 1990.
Travel support is requested for participants. It is anticipated that
airfares will be required for four participants. Hotel accommodations will be
required for eight invitees and the convener. Two days per diem support is
requested for each of the eight invited participants. Other items that are
budgeted include 0.5 man-months secretarial salary support, motor vehicles to
provide travel support for CBL participants, funds to produce a workshop
report, and clerical/secretarial supplies and materials. A small
"miscellaneous" budget category is included to cover any unanticipated costs.
The Chesapeake Biological Laboratory and CEES will not charge indirect costs
on the workshop contract.
Workshop Product
A draft report will be delivered to Maryland DNR by 10 February 1990.
The final report will be issued as a Coastal and Environmental Policy Program
(CEPP) document through the Chesapeake Biological Laboratory.
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APPENDIX B
Ichthyoplankton Workshop Attendees
Ray S. Birdsong
*Victor A. Crecco
Louis Rugolo
Harry T. Hornick
Phil Jones
Michael Hirshfield
Fred Jacobs
*John E. Olney
Patsy Heasly
Steve Jordan
Jim Uphoff
*William A. Richkus
*Paul Rago
Rob Magnien
*Donald Boss
*Geoffrey C. Laurence
*Eileen M. Setzler-Hamilton
James H. Cowan, Jr.
Edward S. Rutherford
Colleen E. Zastrow
Letty C. Fernandez
(Secreatrial Support)
**Edward D. Houde
*Invited Experts
**Convener
Old Dominion University
Connecticut DEP
MD DNR
MD DNR
MD DNR
MD .DNR
Coastal Environmental Services
VA Institute of Marine Science
EPA-CBLO
MD DNR
MD DNR
VERSAR, Inc.
U.S. Fish & Wildlife Service
MD Dept. of Environment
NMFS, Beaufort Lab., N.C.
NMFS, NEFC, Narragansett, R.I.
CBL
CBL
CBL
CBL
CBL
CBL
(804) 683-3595
(203) 443-0166
(301) 974-3782
(301) 974-2241
(301) 974-3782
(301) 974-3782
(301) 684-3324
(804) 642-7334
(301) 266-6873
(301) 974-3767
(301) 974-3767
(301) 964-9200
(304) 725-8461
(301) 631-3681
(919) 728-8746
(401) 782-3200
(301) 326-4281
(301) 326-4281
(301) 326-4281
(301) 326-4281
(301) 326-4281
(301) 326-4281
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APPENDIX C
Issues and Topics to be Addressed at the Workshop
1. Egg Production Estimates
2. Spawner Biomass Estimates
3. Long-term Trends in Species Abundance
4. Definition of Spawning Areas and Times, and Changes over Time
5. Defining Spawning Success and Relating to Environmental Factors
6. Recruitment Predictions
7. Indices of Community Structure
8. Determination of Environmental and Habitat Criteria for Reproductive
Success
9. Causes of Mortality of Early Life Stages
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APPENDIX D
Questions to be Addressed at the Workshop
1. Why monitor ichthyoplankton? What questions could be answered?
2. What useful indices can we obtain?
3. When is ichthyoplankton monitoring better than that on other life stages
of fishes?
4. Can we define critical habitats and environmental parameters from
ichthyoplankton monitoring?
5. Is the lack of an ichthyoplankton monitoring component in the Chesapeake
Bay Monitoring Program a serious omission?
6. What can be gained from ichthyoplankton research as opposed to monitoring?
7. How long must we monitor ichthyoplankton to achieve goals?
8. When and on what time scales should we monitor ichthyoplankton?
9. For what kinds of species will ichthyoplankton monitoring be most
effective?
10. Is ichthyoplankton surveying or monitoring cost-effective?
11. What research questions on estuarine and anadromous species can be
addressed effectively by ichthyoplankton studies?
12. Are there research needs separate from monitoring needs with respect to
Chesapeake Bay ichthyoplankton programs?
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APPENDIX E
ICHTHYOPLANKTON WORKSHOP
Lord Baltimore Hotel
Baltimore, Maryland
Tuesday, 5 December 1989
AGENDA
E. Houde
E. Houde
M. Hirshfield
R. Birdsong/J. Olney/
F. Hoffman
M. Hirshfield
(or designee)
R. Magnien
09:00 Introductions and Welcome
09:05 Objectives and Goals
09:15 Ichthyoplankton Research and Monitoring
in the Maryland Chesapeake Bay
09:30 Ichthyoplankton Research and Monitoring
in the Virginia Chesapeake Bay
09:45 Chesapeake Bay Stock Assessment Committee
(CBSAC), Fishery-Independent Assessments
09:55 Chesapeake Bay Monitoring Program
10:15 Comments and Discussion
10:30 Break
10:45 Plenary Discussion — Issues/Topics
12:00 Lunch (catered Deli Lunch)
1:00 Group Discussions (Three Working Groups meet separately and
develop recommendations)
3:15 Break
3:30 Plenary Discussion and Recommendations
4:30 Adjourn
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APPENDIX F
Working Groups
Group I.. Reproductive Success, Spawning Areas and Times, Environmental and
Habitat Criteria.
Donald Boss (Chair), Eileen Setzler-Hamilton, William Richkus,
Fred Jacobs, Steve Jordan, Michael Hirshfield and Patricia Heasly,
Group II. Egg Production and Spawner Biomass Estimates, Trends in Species
Abundances, Indices of Community Structure.
Paul Rago (Chair), Raymond Birdsong, Colleen Zastrow, John Olney,
Harry Hornick and Robert Magnien.
Group III. Causes of Mortality, Early Life Stage Dynamics and Recruitment
Predictions.
Geoffrey Laurence (Chair), Victor Crecco, Phillip Jones,
James Uphoff, Louis Rugolo and James Cowan.
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