Resource Ecology & Fisheries Management (REFM) Division

Resource Ecology & Ecosystem Modeling Program

Kerim Aydin Is New REEM Program Leader

Kerim Aydin was appointed Program Leader of the Resource Ecology and Ecosystem Modeling (REEM) Program as of 13 June 2005. Kerim received a B.S. in mathematical biology from Harvey Mudd College (1992), and a Ph.D. in fisheries from the University of Washington (UW) (2000), with a dissertation on the impacts of climate and prey variation on the ocean growth of Pacific salmon. He has been a postdoctoral research associate and fishery research biologist with the AFSC since 1999. Kerim’s main research focus has been on fish trophic interactions, bioenergetics, and ecosystem-scale predator/prey models. He has been an affiliate faculty member of the UW School of Aquatic and Fishery Sciences since 2003 and is serving as cochair on the North Pacific Marine Science Organization (PICES) Climate Forcing and Marine Ecosystems Task Team.

By Kerim Aydin
 

Fish Stomach Collection and Lab Analysis

Laboratory analysis was performed on 1,042 groundfish stomachs from the eastern Bering Sea, 992 from the Gulf of Alaska, and 2,877 from the Aleutian Islands region. During this quarter, 627 stomachs were returned by fishery observers and no stomachs were returned from research vessels in the Bering Sea or the Gulf of Alaska. A total of 8,395 records were added to the groundfish food habits database. Stomach collection and shipboard stomach analysis is ongoing for the 2005 field season.

Figure 1.  Diet composition (% wet weight) by wingspan of two species of skates from the 2002 Bering Sea Slope survey.

Recent completed laboratory analyses include the 2002 Aleutian Islands and Bering Sea Slope biennial surveys. Data are also available from these surveys conducted in 2004 due to shipboard analyses of stomach contents beginning that year. Figure 1 shows a subset of diet data from the 2002 Bering Sea slope survey. Aleutian skates (Bathyraja aleutica) are distributed over the shallower portions of the slope (majority of biomass at less than 400 m depth) and have a progression in diet, with size, from small zooplankton to shrimp to walleye pollock. Black skates (B. trachura) are distributed below 600 m and primarily consume deep dwelling crabs at larger sizes. A broader comparison of skate diets throughout the Alaska regions is in preparation.

By Kerim Aydin, Troy Buckley, Geoff Lang, and Mei-Sun Yang
 

Multispecies and Ecosystem Modeling

Kerim Aydin, Jesus Jurado-Molina, Ivonne Ortiz, and Sarah Gaichas participated in a 2-day review of REEM multispecies and ecosystem models conducted by the Center for Independent Experts (CIE). The CIE peer review panel focused on food habits data collection, modeling methods, modeling implementation (coding), and interpretation of results. A final report is expected in the summer quarter.

By Kerim Aydin
 

Ecosystem Considerations

The Ecosystem Considerations section for 2006, part of the Stock Assessment and Fishery Evaluations (SAFE) report (Appendix C), was updated in June 2005 and distributed to stock assessment authors and plan team members. The Ecosystem Considerations section is utilized to advance our understanding of marine ecosystem dynamics and deliver ecological, oceanographic, climatic, and anthropogenic indices to stock assessment scientists and managers.

Interesting trends in some status and trend indicators were seen in 2004. For example, the number of northern fur seal pups born on the Pribilof Islands continued to decline. However, increases in Steller sea lion nonpup counts were observed in 2004 in all areas except the central GOA (slight decline) and the eastern GOA (similar counts as 2002). These time series are updated biennially, and updates to these time series in 2006 will indicate whether these trends in marine mammal populations continued.

Time trends in bycatch of prohibited species are examples of ecosystem-based management indices that may provide early indications of direct human effects on ecosystem components or provide evidence of the efficacy of previous management actions. Interestingly, the bycatch of "other salmon" and herring increased markedly in 2003 and 2004. Between 2002 and 2003, herring bycatch increased more than 600% and "other salmon" bycatch more than doubled. After the dramatic increase in 2003, the herring bycatch increased again by about 42% and "other salmon" bycatch almost doubled in 2004.

Most of the herring bycatch in all years occurs in the Bering Sea-Aleutian Islands (BSAI) trawl fisheries, primarily during the months of July, August, and September with smaller amounts in January through March and October. The recent rise in bycatch can be partly explained by increases of herring biomass; the biomass of Kuskokwim herring, for example, is estimated to have increased by about 34% in 2003 and about 32% in 2004. Observer data reveals differences in the distribution of both effort (all pelagic-trawl hauls) and bycatch (hauls with herring in the species composition) over the years 2002-04. In most months of 2003 and 2004, the amount of effort and bycatch increased noticeably in the northwestern-most portions of the fleet’s range compared to 2002.

Part of the 2003 increase in "other salmon" bycatch could be explained by the 33% increase in the overall catch of "other salmon" in 2003 compared to 2002. The "other salmon" bycatch nearly doubled again in 2004, despite an almost 6% reduction in the overall catch. In 1994, the North Pacific Fishery Management Council (NPFMC) and NMFS established the Chum Salmon Savings Area (CSSA), an area in the Bering Sea closed to trawling in August to minimize chum salmon bycatch. Unfortunately, in both 2003 and 2004 the highest chum salmon bycatch rates were outside of the CSSA and after its closure.

Similar problems occurred in 2003 and 2004 with chinook salmon bycatch outside of the Chinook Salmon Savings Area—the highest bycatch rates were encountered by the pollock trawl fleet outside of the Savings Area after regulations had forced its closure. The resulting chinook salmon bycatch was about 28% higher in 2003 and 41% higher in 2004 than the long-term average over the period 1994-2002. To address these problems, the Council is considering other means to control salmon bycatch.

By Jennifer Boldt and Terry Hiatt


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AFSC Quarterly Research Reports April-June 2005