Growth of chum salmon in relation to population abundance and climate in the eastern north Pacific Ocean and the recruitment of pollock in the eastern Bering Sea

Abstract

Global climate change is expected to change the distribution and growth of marine species. Therefore, understanding how climate, ocean productivity, and population abundance affect the dynamics of marine species will help predict how growth and recruitment of marine species will respond to future changes in climatic and oceanic conditions. Statistically significant intertemporal correlations have been observed between a variety of environmental factors and recruitment, growth, mortality, and abundance of fish populations. However, because these correlative relationships are not reflective of the actual biophysical processes, the relationships can break down, particularly when used for forecasting. Failure of these simple correlative relationships motivates the search for biological indicators that integrate ocean productivity across ecological dimensions and through time. Measured distances along Chum Salmon (Oncorhynchus keta) scale radii and associated body morphology were used to construct time series of Chum Salmon growth and, by extension, time series of productivity of those ecological domains salmon have exploited. Seasonal and annual marine growth of Chum Salmon from Fish Creek, Alaska and Quilcene River, Washington were examined in relation to population abundances and climate indices, 1972-2004. Final body size at maturity of these Chum Salmon was associated with variation in immature growth incurred while in oceanic waters. Density-dependent effects and climate explained some of the variation in growth but did not account for the entire increase in size at maturity in the mid-1990s. In the Bering Sea, Chum Salmon growth was assessed as an indicator for the recruitment of Walleye Pollock (Theragra chalcogramma) to age-1 in an effort to support an ecosystem-based fisheries management. Chum Salmon growth and the maximum of the monthly sea surface temperature explained 85% of the variation in age-1 Walleye Pollock recruitment. Higher Walleye Pollock recruitment success was associated with the combined effect of a cool late summer and intermediate growth of Chum Salmon. The combination of a physical and biological indicator served as the best indicators for changes in the marine growth of Chum Salmon and for the recruitment of Walleye Pollock.