Rep16 - EXECUTIVE SUMMARY

## EXECUTIVE SUMMARY

This report summarizes discussions of a workshop held at the Battelle Conference Center in Seattle, Washington on 31 January-2 February 1996 in anticipation of potential future funding for a U.S. GLOBEC program in the North Pacific. Twenty-three oceanographers or fishery scientists attended the workshop. After initial plenary sessions the participants divided into two groups: one to discuss the Bering Sea and one focusing on the Subarctic Pacific. Each group developed hypotheses that could become the basis for U.S. GLOBEC science in those regions. The hypotheses, target species and recommended approaches for research in the Subarctic Pacific and Bering Sea regions of the North Pacific are detailed in the report.

### Subarctic Pacific Program

#### Hypotheses

- Ocean survival of Pacific salmon is determined primarily by survival of juvenile salmon in coastal regions, and is affected by interannual and interdecadal changes in Gulf of Alaska physical forcing.

- Variation in size-at-age of returning salmon is determined largely by interdecadal and interannual variation in physical conditions and productivity of the oceanic realm of the subarctic Pacific, and may show density dependence.

#### Target Species

- Salmon (esp. pink salmon, Oncorhynchus gorbuscha)
- Prey of salmon, but especially large calanoid copepods and euphausiids
- Predators of salmon (pollock; herring; marine mammals; birds)

#### Approaches

The group elected to focus the Subarctic Pacific Program on the first of the two hypotheses listed above, because that aspect--focusing on factors influencing survival of the juveniles during the nearshore phase of their ocean life history--appeared amenable to a U.S. GLOBEC regional study. Following the general U.S. GLOBEC strategy, the group recommended monitoring, process-studies, modeling and retrospective analysis. A potential study region on the continental shelf outside of Prince William Sound in the Northern Gulf of Alaska was identified as a potential site for U.S. GLOBEC studies because it complements and will benefit from 1) ongoing investigations by the Exxon Valdez Oil Spill Trustees Sound Ecosystem Assessment (SEA) program in Prince William Sound, and 2) planned (or ongoing) shelf-wide surveys of the distribution of juvenile salmonids by the Ocean Carrying Capacity (OCC) program of the Auke Bay Laboratory of the National Marine Fisheries Service (NMFS). Large-scale monitoring of the region should be accomplished through a combination of remote sensing and a few strategically placed moorings, drifters, ship-visited transects, and modeling. Intensive process studies should be conducted for several years in one or more of the regions surrounding the repeat transects and moorings comprising the monitoring system. The focus of the process studies would be to examine the biological and physical processes that determine growth and survival of juvenile salmon in the coastal zone. This would require observations of a) the physical environment, b) secondary production processes, c) diet of juvenile salmon and their competitors and predators, d) the distribution and abundance of salmon predators, and e) growth rates of juvenile salmon. Recommendations for specific retrospective and modeling studies were also made, but the group focused on the monitoring and process-oriented aspects of a subarctic Pacific U.S. GLOBEC study.

### Bering Sea Program

#### Hypotheses

- Zooplankton production in the Bering Sea is primarily directly or indirectly controlled by four physical processes: a) advection, b) stratification, c) sea ice coverage, and d) water temperature (the extent of the cold pool).

- Annual zooplankton production is primarily controlled by predation and interannual variability is controlled by the distribution and abundance of higher trophic level predators.

- Zooplankton production is jointly controlled by the physical processes and the predator-related processes as described in the above two hypotheses.

#### Target Species

- Zooplankton (copepods; euphausiids)
- Seabirds (Least Auklet)
- Pelagic Fish Stocks (pollock; herring; sockeye, pink and chum salmon)
- Forage Fish Species (capelin; sand lance; myctophids; bathylagids)
- Other Invertebrates ("jellyfish"; cephalopods; chaetognaths)
- Other large predators (northern fur seals; kittiwakes; murres; piscivorous flatfish; Pacific cod)

#### Approaches

This working group also discussed monitoring, modeling, retrospective analysis and process-oriented studies. In addition, they also discussed technology related issues. In the arena of retrospective analysis, a key problem is to establish the pattern of natural variation in physical forcing and ecosystem response. Biological data sets available to examine this include walleye pollock and sockeye salmon population abundances, and salmon migration pathways. Physical data include information on ice extent, some temperature data, and several atmospheric variables. A suite of types of physical, biological and coupled biophysical models in the Bering Sea were discussed and should be supported. Monitoring efforts should focus on acquiring observations of the physical, chemical and biological environment to examine interannual variability over an extended period. Several regions were identified as valuable sites for monitoring of physical (e.g., transport through Amukta Pass; ice-edge position, melting cycles because of its influence on productivity; transport processes in the Unimak Pass, an indication of Alaskan Coastal Current strength) and biological (Pribilof Island region, because of the extensive ecosystem work, especially on higher trophic level organisms) processes. Process-oriented studies should focus on the key species and the factors which control their production. Thus, they should be conducted at the appropriate space and time scales to examine zooplankton and fish production in relation to physical features (fronts, eddies, position of the ice edge, extent of the cold pool) that may vary both seasonally and from year-to-year. Advancements in optical, acoustical and biomolecular technology that permit more resolution (or comprehensive) sampling should be employed in a U.S. GLOBEC Bering Sea program.