There has been recent concern that the North Pacific Ocean appears to be showing signs of distress. Most dramatic are the precipitous declines in seabird and marine mammal populations in Alaskan waters. Recognizing that humans tend to consider peaks in populations to be normal and desirable for sustained population size, we have to admit that we do not know the normal fluctuations in these populations. Clearly, though, the intense fishing activity in the Bering Sea provides an additional factor which the ecosystem did not have to accommodate in the past. Large excess harvesting capacity exists, which places a stress on the Bering Sea, and requires management tuned to the system as a whole.
The ecosystem of the southeast Bering Sea contains two fairly distinct upper-trophic level species groups or guilds based on characteristics of feeding. The first group consists of an outer shelf pelagic group of fish, mammals and birds that consume small fish, primarily juvenile pollock, and euphausiids. The second group is an inshore group of fish, crab and other bottom dwelling fauna that consume mainly benthic infauna. These two groups represent a biomass of about 8-10 million metric tons each, making the southeast region the major commercial sector of the Bering Sea. Walleye pollock dominate the biomass of the outer shelf and the species diversity of the pelagic guild is low. This low diversity contributes to potential lack of stability in the present Bering Sea. If this hypothesis is true, research that elucidates processes that influence interannual to decadal scale changes in the production of walleye pollock provides an indicator of the health of the ecosystem.
We plan to examine juvenile pollock in terms of their linkages to other species. Production is influenced by their overlap in space and time with predators and the distribution of secondary productivity. The oceanography of the southeast Bering Sea consists of at least five distinct habitats which mediate this overlap. We propose a regional ecosystem study which will 1) conduct retrospective analyses of the role of pollock in the ecosystem since the 1960s, 2) characterize the fisheries biology and fisheries oceanography of the distinct habitats, and 3) develop spatially explicit models for the early life history of juveniles and upper-trophic level interactions. The project will be highly leveraged, including primary interactions with marine mammal studies and foreign research laboratories, and will provide products to the North Pacific Fishery Management Council.