Iceland CCC Symposium

## International Symposium Examines Climate Change Effects on North Atlantic Cod Stocks

### by Harold P. Batchelder

Several members of the community of U.S.GLOBEC scientists attended the ICES Symposium on Cod and Climate Change, in Reykjavik, Iceland, 23-27 August. We were welcomed to Reykjavik, Iceland by the President of Iceland, Vigdis Finnbogadottir. She noted how it was appropriate that Iceland host the symposium on Cod and Climate Change since historically, cod (and fish, generally) have been extremely important to the people of Iceland. Farms were too unproductive to sustain a family and fish were an important food of the earliest Icelanders. The President quoted an old Icelandic saying, "Lifid er saltfiskur"--translated "Life is Fish". In days past, codfish were a form of currency, with one cow equal in value to several "well-fed" ewes or "240 fat and juicy fish". Further illustrating the importance of fish, and especially cod, to the Icelanders is the Insignia of Iceland (Icelandic Coat of Arms introduced in 1591) which depicts a split, dried cod with a crown. Following the President's welcoming address, we enjoyed three Icelandic Folk songs, a Finnish boat song, and an Irish Folk song performed by a choir of young Icelandic singers. All in all a very pleasant, and unexpected, way to open an international symposium. After the President of ICES, D. de G. Griffith, and the convenor of the symposium, Jakob Jakobsson made their opening remarks, the scientific sessions began. One advantage to the ICES symposium format is that there is only a single scientific session at one time--meaning that the participants are able to hear every presentation. For the Cod and Climate Change (hereafter CCC) symposium, the presentations were divided into eight scientific sessions.

Session 1. Historic Overview. [4 oral, 3 posters]--This session highlighted changes in cod stocks and cod fisheries using diverse data sources ranging from anecdotal reports from Icelandic Annals, population trends, taxation levels, more recent catch statistics, and bioarcheology (estimation of the size of codfish from bones found in archeological sites).

Session 2. Diagnosis of the causes of trends and fluctuations in cod stocks, with reference to environmental influences, anthropogenic influences (fishing, pollution), and interactions with other species (including marine mammals and birds). [12 oral, 3 posters]--During this session overviews were presented of changes in both fisheries and environmental factors for each distinct major cod stock. NW Atlantic (Georges Bank, Scotian Shelf, Gulf of St. Lawrence, Labrador and Newfoundland), Iceland-Greenland complex (Greenland and Iceland stocks), NE Arctic (Arcto-Norwegian stock) and marginal or enclosed sea (North Sea and Baltic) stocks were discussed.

Session 3. Physical (meteorological and oceanographic) processes and models of a) North Atlantic circulation and shelf systems and b) regions of importance of cod, with special emphasis on changes to be expected in the physical environment of cod. [5 oral, 4 posters]--Papers in this session directly addressed the focus of the symposium--how does (or has) climate affected the abundance and/or distribution of cod in the North Atlantic. Large-scale circulation changes, effects of the Great Salinity Anomaly, and shelf circulation are some of the "climate-related" processes that were demonstrated (or hypothesized) to affect the physical environment of cod.

Session 4. Models of bio-physical processes influencing the dynamics of cod populations. [7 oral, 3 poster]--Papers in this session ranged from effects of the environment on the smallest scales influencing swimming and feeding behavior of larval cod, and fertilization success of spawned eggs, to larger scale advection and transport and its effects on residence times of cod eggs and larvae in suitable habitat. Dr. Gregory Lough (National Marine Fisheries Service, Woods Hole) presented results from a modelling study of retention time of cod eggs and larvae on Georges Bank that he and his coworkers have done with U.S. GLOBEC funding.

Session 5. Biology of cod (eggs, larvae, juveniles, and adults), stock identity, migration, stock structure, recruitment processes, and population dynamics. [16 oral, 19 posters]--This, the largest, session included presentations on a broad range of issues related to stock structure (age and size at maturity, growth dynamics, temperature preferences, migration patterns) and recruitment--all with a view towards the effects of environmental conditions, and changes thereof, as a determinant of observed patterns. Most presentations were restricted to results from a single cod stock. Dr. Keith Brander (Lowestoft, UK) argued that the research findings accumulated for separate regional cod stocks are of considerable value in generating hypotheses when compared inter-regionally. Through such comparisons of patterns of occurrence, growth and survival in different areas, ideas may emerge that are not evident from single site results alone.

Session 6. The position of "king cod" in the various ecosystems and relevant management implications, e.g., prey and predators of eggs, larvae, juveniles and adult cod. [5 oral, 3 posters]--This session examined trophodynamic aspects of cod, including predation of cod on capelin and their own species (cannibalism) and predation upon cod by invertebrates, fish, mammals and birds.

Session 7. Experimental studies of the biological performance at various stages of the life history. Spawning, larval survival, maturation, and growth of cod from contrasting environments. [6 oral, 4 posters]--Papers in this session discussed egg production, effects of the environment on eggs and the behavior of cod larvae, and the influence of egg size on egg and larval survival.

Session 8. Studies on physiology and genetics, particularly those which indicate the response of cod under changing environmental conditions. [5 oral, 7 posters]--The linkage between identifiable genetic structure and physiology was a focus of the papers presented in this session, as were the role (and especially ontogenetic changes in the amount) of antifreeze proteins in cod survival and distribution (off Labrador) and new genetic techniques of identifying geographic and parentage variation.

### Summary

The meeting was excellently organized and the presentations, and discussions, were very informative. There is a great deal known about cod stocks--both in fisheries and cod biology generally--and the presenters, with few exceptions, directly addressed the issue of cod stocks and cod biology and how they are affected by environmental (climate) change. One theme that came through clearly from the talks and ensuing discussions at the CCC symposium is that most North Atlantic cod stocks have been harvested at levels too high to be sustained. Consequently, many of the abundance (catch) fluctuations in cod stocks are due to fishery-related activities--implementation of new gears, fishing restrictions, or quotas.

The impact of climate or changing physical environment on the cod stocks of the North Atlantic may be small compared to the effect that fishing has had (to date) upon the stocks. Changing environmental conditions, coupled with high harvesting rates, may have accelerated declines in the abundance and structure of some cod stocks. Overall, however, it is unclear where and how we will see climate change in the North Atlantic. Will it be a basin-wide effect, or a local effect? If local, evidence suggests that each cod stock will respond differently. Examples of climate change effects on specific cod stocks were provided in a paper by Bob Dickson and Keith Brander. They document (1) changes in advection affecting the West Greenland stock--i.e., advection of larvae from Iceland that reach West Greenland and then grow up there, (2) effects of the Great Salinity Anomaly on Barents Sea cod stocks, (3) effects of windspeed changes on the Faroes Bank cod--acting through the effect of windspeeds on production, feeding and condition of larval cod, and (4) climate driven changes in the frequency of replacement of low oxygen water with high oxygen water in the Baltic--which changes the volume of the Baltic having conditions suitable for cod egg development and hatching, and larval development.

Nearly all speakers at ICES symposia arrive with several hundred copies of their (nearly) completed manuscript which are subsequently distributed at the meeting on the day of their presentations. The proceedings of this symposium will be published by ICES--but may take a year or more. In the meantime, a list of the titles, authors names and senior authorŐs address are available from Omnet Bulletin Board GLOBEC.STATUS (Message Titled: ICES CCC Titles) for those who are interested in contacting the author directly for a copy (preprint) prior to publication. Alternatively, the list can be provided via internet by requesting it from Hal Batchelder at internet address halbatch@violet.berkeley.edu. Please specify that you want the ICES CCC Titles and Abstracts.

A Congress Dinner of cod and lamb (two Icelandic staples) followed the closing of the scientific sessions. During these closing dinners at ICES symposia it is apparently traditional for the participants of each nation to stand together and sing one or more traditional songs of their homeland. Many of the nations had prepared for this and were accompanied by guitar (Norway) or had practiced (Canada even had a very fine soloist--Dr. Sally Goddard). The unprepared U.S. contingent (Dr. Mike Sissenwine and Dr. Brian Rothschild, probably aware of the tradition, having left the symposium already) were led by Dr. Fredric Serchuk (NMFS, Woods Hole) and Dr. Kenneth Brink (Woods Hole Oceanographic Institution)--and accompanied ably by Greg Lough (NMFS, Woods Hole), Jim Meehan (NOAA), Bill Peterson (U.S. GLOBEC Interagency Program Office) and Hal Batchelder (U.S. GLOBEC SSC Office)--in rousing renditions of "Home, Home on the Range" and "Take Me Out to The Ballgame". Thanks, Fred and Ken. (Hal Batchelder is an administrative analyst with the U.S. GLOBEC Coordinating Office at UC Berkeley, and a biological oceanographer when time permits)