Rep16 - Bering Sea Program

## Bering Sea Program

Working Group Members: Vera Alexander, Ric Brodeur, Anne Hollowed, James Ianelli, Thomas Loughlin, Tom Powell, Alan Springer, Phyllis Stabeno, Trey Walker, and Warren Wooster

### Program Rationale

The biological richness of the large shelf and marked similarities in biophysical processes to those found in other large marine ecosystems provide compelling reasons for a U.S. GLOBEC program in the eastern Bering Sea. Annual variation of solar radiation, atmospheric conditions, ice cover and water column structure fueled by a flux of nutrient-rich slope water results in one of the world's most prolific ecosystems (Niebauer et. al. 1990). Primary production over the shelf often begins with a bloom associated with ice-melt (Walsh et. al. 1989) and a "greenbelt" of annual production (>200 gC m-2) occurs over the outer 200 km of the shelf/slope (Schumacher and Reed 1992). The accompanying zooplankton production supports vast populations of migratory marine mammals, birds, fish, and shellfish. The pollock fishery constitutes one of the largest single species fishery in the world and the run of sockeye salmon into Bristol Bay, Alaska, is one of the worldıs largest (45 million adult salmon predicted for 1996). Shellfish and fish harvest from the region represented 40% of the annual U.S. commercial fish harvest in 1994.

The physical and biological characteristics of the Bering Sea lend themselves to comparisons with other world oceans. The Bering Sea shares several similarities to the Barents Sea ecosystem off the Coast of Norway (Schumacher 1987). The opportunity to draw comparisons between northern latitude seas could be particularly fruitful given the existence of the ICES Cod and Climate program. Comparisons of climatic regimes between the Barents Sea and the Bering Sea suggest that teleconnections exist that produce oscillating periods of low or high atmospheric pressure that persist for 6-12 years. Both regions are heavily influenced by seasonal ice coverage that is directly linked to atmospheric circulation. Like the Barents Sea, the Bering Sea ecosystem is dominated by three pelagic fish species groups [gadids (cod or pollock), herring and capelin] and a large demersal flatfish population. Likewise, the two regions have historically supported large pinniped populations.

The Bering Sea ecosystem also shares many notable similarities to Georges Bank, the focus of an ongoing U.S. GLOBEC program in the Northwest Atlantic. Fluctuations in the boundary location of two major air masses in both regions effects the physical characteristics of the ecosystem by influencing winds, advection, and air and sea temperature. Like Georges Bank, the Bering Sea exhibits readily identifiable physical features that directly influences the distribution of marine fish (i.e., the cold pool in the Bering Sea, bank circulation in Georges Bank). Similar to Georges Bank, tidal currents play an important role in both mixing and generation of residual flow at frontal features (Coachman 1986). Both regions historically supported large populations of commercially important gadids [i.e., Pacific cod (Gadus macrocephalus), walleye pollock (Theragra chalcogramma), Atlantic cod (Gadus morhua), haddock (Melanogrammus aeglefinus)] which consume similar zooplankton genera (Calanus and Pseudocalanus) during early life stages. Research on the Bering Sea ecosystem provides an opportunity for comparative studies on the response of copepod and gadid populations to changes in physical regimes in two separate but somewhat parallel regions. Both ecosystems are seasonal feeding grounds for migratory pelagic predators: Atlantic mackerel (Scomber) in Georges Bank and Pacific salmon (Oncorhynchus) in the Bering Sea.