RESOURCE ECOLOGY & FISHERIES MANAGEMENT (REFM) DIVISION (cont.)

Resource Ecology & Ecosystem Modeling Program

Fish Stomach Collection and Content Analysis

Laboratory analysis was performed on 2,285 fish stomachs from the eastern Bering Sea, 55 fish stomachs from the Gulf of Alaska and 2,422 fish stomachs from the Aleutian Islands. At-sea analysis was performed on 1,900 fish stomachs from the eastern Bering Sea slope and 1,563 fish stomachs from the Aleutian Islands. Stomach samples were collected from 2,353 fish from the Bering Sea shelf (including samples from the western shelf) and from 42 fish in the Aleutian Islands during AFSC surveys. Observers returned 441 stomachs from Bering Sea fisheries during this quarter. A total of 7,693 new data records were added to the groundfish food habits database.

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


Ecosystem Considerations for 2005

The first draft of the Ecosystem Considerations Section for 2005 was completed as part of the Stock Assessment and Fishery Evaluation (SAFE) Reports, which are provided to the NPFMC annually. A summary of the first draft was presented to the NPFMC groundfish plan teams 17 September 2004. The section content and format has changed slightly from last year and is comprised of three parts: the Ecosystem Assessment, Ecosystem Status Indicators, and Ecosystem-Based Management Indices and Information.

The Ecosystem Assessment this year focuses on the historical responses of ecosystem components to climate regime shifts and provides expert judgment on the near-future state of the climate. This assessment was derived primarily from a PICES study group report providing advice to the United States on the effects of climate on fisheries. Based on basin-wide North Pacific climate-ocean indices, there appears to have been a major regime shift in 1977, a minor shift in 1989, and recent shift in 1998. For regimes prior to 1977, the pattern of sea surface temperature spatial variability implied a west-east dipole. Since 1989, the pattern of spatial variability has been dominated by a second pattern of sea surface temperature variability, which implies a north-south dipole.

In the Bering Sea (BS) and Gulf of Alaska (GOA), the major atmospheric shift of 1977 resulted in a change from a predominantly cold climate to a warmer maritime climate as part of the Pacific Decadal Oscillation (PDO). Responses of various physical and biological indices to the 1977 and 1989 regime shifts can be seen in newly created tables of time series anomalies in the Ecosystem Assessment. For example, after 1977, salmon catches increased in the BS and GOA, GOA shrimp survey catch-per-unit-effort CPUE decreased, and survival indices of some groundfish shifted. Given the variability in indices since 1998, there is some uncertainty about the level of productivity of the new regime; however, there is growing evidence that there are strong responses in the California Current ecosystem and weak evidence of responses in the GOA ecosystem. It is projected that the Bering Sea will most likely continue on its current warm trajectory, with biomass transitioning northward allowing walleye pollock a larger domain at the expense of cold- and ice-adapted species, rather than transitioning back to a cold regime. It is currently unclear if changes observed in the GOA after 1998 will persist. For example, shrimp CPUE in the north GOA increased from 1998 to 2001 but has since decreased again.

The next draft of the Ecosystem Assessment will include some information on ecosystem models that will be used to summarize possible future effects of climate and fishing on ecosystem structure and function. Currently, not all of the modeling tools are ready for use in projections; however, future development of modeling tools will enable scientists to provide advice on management strategies that are robust to a wide range of future ecosystem states. The assessment could be used to evaluate aggregate effects of groundfish fisheries on ecosystem and habitat and could result in advice regarding changes in aggregate catch levels (OY cap), species mix of the catch, and discard amounts. The assessment this year also provides a more analytical presentation of the historical trend and variation in key indicators in a graphical red/green indicator table that indicates direction and magnitude of indicator changes over time.

The Ecosystem Status Indicators section summarizes the historical trends and current status of physical, biological, and community or ecosystem-level indices. New this year is the addition of status and trend information pertaining to nutrients and productivity; age-0 pollock diet, distribution, and energy content in the Bering Sea; error bars on bottom trawl survey CPUE estimates of forage fish, HAPC, and miscellaneous species; a regime-shift analysis of recruit-per-spawning biomass anomalies; and a detailed summary of Alaska Native Traditional Environmental Knowledge of climate regimes. Data gaps still include lower trophic levels, such as phytoplankton, and zooplankton information.

The Ecosystem-Based Management Indices and Information section contains updated indices that are intended to provide either early signals of direct human effects on ecosystem components or to provide evidence of the efficacy of previous management actions. Indices presented address four main goals of ecosystem-based management that the NPFMC proposed: maintain diversity, maintain and restore fish habitats, ensure sustainability, and include humans as part of the ecosystem.

Stock assessment scientists continued to use indicators from the Ecosystem Considerations section to assess ecosystem factors such as climate, predators, prey, and habitat that might affect a particular stock. Also, information regarding a particular fishery’s catch, bycatch, and temporal/spatial distribution was used to consider the possible impacts of that fishery on the ecosystem although updated non-target species catch data were not available this year. We are still in early stages of using this type of information in stock assessments. However, we anticipate the information could be used to modify allowable biological catch recommendations or spatial/distribution of the catch due to ecosystem concerns, or to target further research that would be needed to quantify ecosystem impacts.

By Jennifer Boldt


Seabird-Fishery Interaction Research

Efforts to characterize seabird incidental take within the Alaskan groundfish fisheries continued during this quarter. A U.S. North Pacific Groundfish Observer Program special project was expanded in the trawl fleet to identify trawl industry components that have additional sources of mortality due to seabird interactions with third-wire cables, trawl door main cables, and the trawl net itself. In addition to increased efforts to characterize seabird incidental take, we also continued collaboration with the fishing industry and the Washington Sea Grant Program to explore the use of mitigation measures to reduce seabird interactions with fishing gear. Cooperative research funds were awarded to the Pollock Conservation Cooperative to investigate measures to reduce seabird interactions for trawl vessels. This preliminary work will lead to a rigorous field experiment, likely beginning in 2006. We also coordinated with the Observer Program to deploy staff to a longline vessel to work on vessel-specific bycatch reduction. That trip was made in September 2004.

To assist with efforts to monitor seabird/trawl gear interactions, a pilot project was completed in 2002 that employed the use of electronic monitoring to view seabird interactions with trawl third wires. The results of this study, McElderry et al.,2004. Electronic monitoring of seabird interactions with trawl third-wire cables on trawl vessels – a pilot study. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-AFSC-147, 39 p, are available on the AFSC website at http://www.afsc.noaa.gov/Publications/AFSC-TM/NOAA-TM-AFSC-147.pdf. The pilot study, conducted by Archipelago Marine Research Ltd. and the AFSC, involved field testing of electronic monitoring (EM) systems on shoreside delivery and head and gut bottom trawl vessels conducting operations in the Bering Sea, U.S. Exclusive Economic Zone. The EM systems, consisting of two closed circuit television cameras, GPS, hydraulic and winch sensors, and on-board data storage, were deployed on five fishing vessels for 14 fishing trips during a 1-month period in fall 2002. Detailed analysis of about 200 hours of fishing imagery occurred, representing 20 shoreside delivery vessel fishing events and 32 head and gut fleet fishing events. Results from the study demonstrated that EM could effectively monitor seabird interactions with trawl third-wire cables. The EM system provided imagery of sufficient quality to detect the presence, abundance, and general behavior of seabirds during most daylight fishing events. As well, EM-based imagery was also able to detect third-wire entanglements of seabirds although it was not possible to determine the cause of these entanglements. The EM imagery was not very useful for seabird enumeration and species identification. In regard to monitoring seabird interactions with trawl third-wires, EM would be suitable for monitoring the use and effectiveness of mitigation measures.

In other related research, stationary seabird surveys were conducted in conjunction with most haul locations for the summer AFSC groundfish research charters. Data are being collated, and we will work with Washington Sea Grant to combine the trawl and longline research charter information. Staff from both the AFSC and the NMFS Alaska Regional Office participated in the Third International Albatross and Petrel Conference in Montevideo, Uruguay, 22-27 August 2004. Seabird specialists from around the globe gathered to address concerns about the incidental mortality of albatrosses and petrels in commercial fisheries. The conference was attended by participants from every continent and presentations and posters reported on the latest research and information in the fields of: population status and trends, population dynamics, molecular ecology and systematics, general biology and behavior, feeding ecology and foraging area, incidental mortality and mitigation, and conservation policies and international initiatives. Several posters were presented by Alaska Regional Office and AFSC staff.

By Shannon Fitzgerald

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AFSC Quarterly Research Reports July-Sept 2004