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.
