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Marine Ecology Progress Series

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MEPS 370:1-18 (2008)  -  DOI:

Density-dependent growth of Alaska sockeye salmon in relation to climate–oceanic regimes, population abundance, and body size, 1925 to 1998

Ellen C. Martinson1,*, John H. Helle1, Dennis L. Scarnecchia2, Houston H. Stokes3

1Alaska Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration (NOAA), 17109 Point Lena Loop Road, Juneau, Alaska 99801, USA
2Department of Fish and Wildlife Resources, University of Idaho, Moscow, Idaho 83844, USA
3Department of Economics, University of Chicago, 601 S. Morgan Street, Chicago, Illinois 60607, USA

ABSTRACT: To better understand how density-dependent growth of ocean-dwelling Pacific salmon varied with climate and population dynamics, we examined the marine growth of sockeye salmon Oncorhynchus nerka in relation to an index of sockeye salmon abundances among climate regimes, population abundances, and body sizes under varied life-history stages, from 1925 to 1998, using ordinary least squares and multivariate adaptive regression spline threshold models. The annual marine growth and body size during the juvenile, immature, and maturing life stages were estimated from growth pattern increments on the scales of adult age 2.2 sockeye salmon that returned to spawn at Karluk River and Lake on Kodiak Island, Alaska. Intra-specific density-dependent growth was inferred from inverse relationships between growth and sockeye salmon abundance based on commercial harvest. Density-dependent growth occurred in all marine life stages, during the cool regime, at lower abundance levels, and at smaller body sizes at the start of the juvenile life stage. The finding that density dependence occurred during the cool regime and at low population abundances suggests that a shift to a cool regime or extreme warm regime at higher population abundances could further reduce the marine growth of salmon and increase competition for resources.

KEY WORDS: Sockeye salmon · Marine growth · Density dependent · Ocean regimes · Climate change · Body size · Age

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