Geographic variation in Pacific herring growth in response to regime shifts in the North Pacific Ocean.

Pacific herring populations at eight North Pacific Rim locations were simulated to compare basin-wide geographic variations in age-specific growth due to environmental influences on marine productivity and population-specific responses to regime shifts. Temperature and zooplankton abundance from a 3D lower-trophic level ecosystem model (NEMURO) simulation were used as inputs to a herring bioenergetics growth model. Herring in California, the west coast of Vancouver Island (WCVI), Prince William Sound (PWS), Togiak, Alaska, the western Bering Sea (WBS), the Sea of Okhotsk (SO), Sakhalin, and Peter the Great Bay (PGB) were examined. The half-saturation coefficients of herring feeding were calibrated to climatological conditions at each of the eight locations to reproduce averaged size-at-age data. Using the calibrated half-saturation coefficients, the 1948 to 2002 period was then simulated. The detected shifts of herring age-5 growth showed a close match (69%) to the climate regime shift years (1957/58, 1970/71, 1976/77, 1988/89, 1998/99). The first principal component of herring growth rate showed decreased growth at the SO, PWS, WCVI and California locations and increased growth at the Sakhalin, WBS and Togiak locations after 1977. The calibrated half-saturation coefficients affected the degree to which growth was sensitive to interannual variation in water temperature versus zooplankton. For sustainable use of marine resources, knowledge of the local and regional responses of the marine resources is essential. The model results demonstrate how geographic specificity of bioenergetics parameters, coupled with location-specific variation in temperature and food, can combine to determine local and regional responses of a marine resource to climate forcing. The contents are in press on Progress in Oceanography.