Comparison of the effects of climate variations on pelagic ocean habitats and their potential role in structuring the forage fish distributions in the Bering Sea and Gulf of Alaska

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Theoretical ecology suggests that competition between species and predator-prey interactions are modulated by the quality and quantity of suitable habitat. This paper examines whether climate variations influence the boundaries of suitable pelagic habitat, and whether these changes effect the spatial distribution and interactions between key fish species in the Bering Sea and Gulf of Alaska. The study focuses on the summer distributions of forage fish (age-0 and age-1 walleye pollock (Theragra chalcogramma), and capelin, (Mallotus villous). Forage fish distributions were collected during summer acoustic and bottom trawl surveys conducted as part of the NOAA groundfish trawl and acoustic surveys in the Bering Sea in 2003 -2007, and the NOAA Fishery Interaction Team experiments in the Gulf of Alaska conducted in 2000-2006. We compare the responses of age-0 and age-1 walleye pollock, and capelin to climate induced shifts in pelagic habitats in the Bering Sea and Gulf of Alaska ecosystems. Habitat boundaries are defined using key explanatory variables including: forage fish density, predator distribution, depth, bottom temperature, surface temperature, and surface chlorophyll a. General Linear Models are developed to predict the spatial distribution of age-0 pollock, age-1 pollock and capelin in both regions. Comparison of the responses of three classes of forage fish in different ecosystems helps to better understand their expected responses to climate forcing.