Resource Ecology & Ecosystem Modeling (REEM) Program
Fish Stomach Collection and Lab Analysis
During the second quarter of 2008, fishery observers collected 903 stomach samples from the eastern Bering Sea and 176 stomach samples from the Gulf of Alaska. AFSC scientists have begun collecting stomach samples on groundfish surveys of the eastern Bering Sea. Stomach samples were not analyzed at sea this quarter, but 3,170 stomach samples were analyzed in the laboratory.
By Troy Buckley
Ecosystem Modeling
Drs. Sarah Gaichas and Kerim Aydin (Resource Ecology & Ecosystem Modeling (REEM) Program) along with Garrett Odell and Robert Francis (University of Washington) presented innovative food web model applications at the second Advances in Marine Ecosystem Modeling Research (AMEMR) Symposium in Plymouth, England, 22-26 June 2008. The AMEMR Symposium, hosted by the Plymouth Marine Laboratory, was organized to showcase research "bridging the gaps" in today’s ecosystem models, including that between lower and higher trophic levels, and those existing between modeling and experimentation, towards developing the next generation of models. Given the large scale, complexity, and inscrutability of processes in marine ecosystems, an important question addressed by the AMEMR Symposium was where to invest limited resources in experimentation and observation to improve our knowledge for forecasting and management.
In a paper titled "Identifying critical interactions and thresholds in eastern North Pacific ecosystems through model simulations," Gaichas et al. showed how current ecosystem models can be used to identify both critical interactions requiring further study and potential ecosystem thresholds for fishery management. They conducted model simulations for the Aleutian Islands ecosystem by systematically varying vital rates for each species/functional group in the food web and examining cumulative ecosystem responses which incorporated uncertainty. Results identified an interaction between two commercially important species which potentially contributes to instability in the ecosystem. Model simulations for the adjacent eastern Bering Sea and Gulf of Alaska ecosystems displayed different critical interactions, suggesting different research priorities.
In another analysis, they simulated effects of alternative fishing intensities in the Gulf of Alaska ecosystem model to determine whether thresholds existed where fishing fundamentally changed system properties. The challenge of considerable uncertainty in dynamic interaction (predator-prey functional response) parameters was overcome by generating millions of potential ecosystems with interaction parameters drawn at random from wide ranges, and retaining potential ecosystems where all species co-existed for 50 years under the different fishing regimes. They found a clear threshold between moderate and heavy exploitation rates where fishing damaged the robustness of the ecosystem, and was more likely to contribute to system restructuring. Taken together, these types of simulations can help prioritize field and management research which can then be used to further improve models.
By Sarah Gaichas
Seabird Necropsies
The AFSC strives to make full use of seabirds taken in commercial fisheries. Over the years, AFSC staff have partnered with different groups that have obtained funding in support of seabird necropsies. The first such partnership involved the AFSC, the U.S. Fish and Wildlife Service, the U.S. Geologic Survey, and the University of Washington Burke Museum, with funding supplied by the National Science Foundation, to retain seabirds from high-seas driftnets. More recently, the Washington Sea Grant Program (WSGP) arranged for funding to necropsy birds collected under the North Pacific Groundfish Observer Program (by fisheries observers, AFSC staff, and WSGP staff) during studies completed during longline fishery integrated weight mitigation studies operations in Alaska during July to December 2005. North Pacific groundfish observers have continued to collect seabird carcasses since 2005. Many of those birds are now being necropsied through another partnership program with the nonprofit organization Oikonos, which also coordinate with the Seabird Health Study facilities at California State University’s Moss Landing Marine Laboratories.
