Bering Sea Benthic Amphipod Community: Stability/Instability Relative to Changing Oceanographic Conditions and Increased Gray Whale Predation

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AbstractThe northern Bering Sea ampeliscid amphipod bed, covering approximately 40,000 km2, is the most productive benthic community reported. Ampeliscid amphipods are the major prey of gray whales and a significant proportion of the eastern Pacific (California) whale population feeds in the northern Bering Sea. Although the gray whale population has been growing at a rate of 3.29%/yr since 1980, there has been over a three-fold increase in whale mortality in the last year. It has been suggested that this increase in mortality may be due to starvation. A 30% decline in amphipod secondary production between 1986-1988 indicated that the whales may have been approaching the carrying capacity of the Bering Sea amphipod community at that time. Today, they may be food limited.In addition to whale predation, declines in amphipod production, abundance and biomass could be due to a decrease in primary production or changes in phytoplankton species composition, resulting in declines of carbon flux to the seabed. In addition, a temperature regime shift due to recent El Nino events or global warming might also impact ampeliscid populations. This effort will reoccupy stations sampled from 1986 to 1988, using identical techniques. Specifically, it will measure the abundance, biomass, size composition, species composition and production of the ampeliscid amphipod community in the Chirikov Basin, northern Bering Sea. These measurements will permit documention of changes that may have occurred in the feeding regime of the gray whales between 1988 and 2001. Due to their low growth rates and long generation times, the ampeliscid community may be slow to recover from substantial declines in abundance, biomass and production. Given their central role in energy transfer to apex predators, declines in amphipod production, whatever the cause, are likely to alter the ecological community structure in the Chirikov Basin. Such changes may effect not only wildlife and fish resources in the region, but may also negatively impact the native subsistence communities in both Siberia and Alaska.