Resource Ecology & Fisheries Management (REFM) Division

Resource Ecology & Ecosystem Modeling Program

Fish Stomach Collection and Lab Analysis

Laboratory analysis was performed on 2,760 groundfish stomachs from the eastern Bering Sea and 618 stomachs from the Aleutian Islands and Gulf of Alaska. During this quarter, no stomachs were returned by Observers. In total, 9,720 records were added to the groundfish food habits database.

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

Ecosystem Considerations

The Ecosystem Considerations section of the Stock Assessment and Fishery Evaluation (SAFE) document was updated again in 2005 and includes an ecosystem assessment, updated status and trend indices, and ecosystem-based management indices and information. This report is made available to stock assessment scientists and the North Pacific Fisheries Management Council (NPFMC) and the public in the fall of each year, and the information in this report is used in scientific evaluations in stock assessments and the Environmental Assessment that are also provided to management. One of the additions and improvements to the report this year is an executive summary which highlights important and recent trends in climate, biology, and fishing impacts. Also, a new web site has been developed that provides access to the contributions as well as to data time series summarized in the report (online availability is planned for mid-2006).

Notable trends include recent warm conditions in the eastern Bering Sea (EBS) and a long-term warming trend in shallow waters of the Gulf of Alaska (GOA). This year, there were two apparent “red flags” in the EBS. First, there was a persistent decline of summer net zooplankton (e.g., large copepods such as Calanus marshallae), which are important prey for fish, including walleye pollock, seabirds, and baleen whales. If the low abundances of these prey items continue, there may be declines in consumer populations or range shifts northward to areas where these copepods might be expected to remain abundant. The second flag was less certain.

Declines in annual surplus production (ASP) in the EBS were observed, in spite of relatively stable abundances and exploitation levels. Excluding the most abundant groundfish species that dominate observed trends, annual surplus production trends also showed strong and significant declines in all nonpollock species from 1978 to 2004 in the Bering Sea and declines in stocks, excluding pollock and arrowtooth flounder, in the GOA over this same period.

These declines may be a reflection of changes in either annual primary production or changes in food web structure. If these declines in annual surplus production are the result of climate change and if the current climate conditions persist, future fish production in the EBS is expected to be lower than in previous decades. However, if the declines in surplus production are a function of density-dependent factors resulting from moderate to high biomass levels, then the declines are not a “red flag” but rather a natural response to changes in stock size.

By Jennifer Boldt


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AFSC Quarterly
Research Reports Oct-Dec 2005