Abstract
One of the motivations of the GLOBEC Northeast Pacific program is to understand the apparent inverse relationship between the increase in salmon catches in the Gulf of Alaska and concurrent declines in the California Current System (CCS). We therefore used coded wire tag (CWT) data to examine the spatial and temporal patterns of covariability in the survival of hatchery coho salmon along the coast from California to southeast Alaska between release years 1980 and 2004. There is substantial covariability in coho salmon survival between neighboring regions along the coast, and there is clear evidence for increased covariability within two main groups – a northern and southern group. The dividing line between the groups lies approximately at the north end of Vancouver Island. However, CWT survivals do not support inverse covariability in hatchery coho salmon survival between southeast Alaska and the CCS over this 25 year time span. Instead, the hatchery coho survival in southeast Alaska is relatively uncorrelated with coho survival in the California Current System on inter-annual time scales. The 50% correlation and e-folding scales (distances at which magnitude of correlations decreases to 50% and e−1 (32.8%), respectively) of pairwise correlations between individual hatcheries were 150 and 217 km, which are smaller than that reported for sockeye, pink, and chum salmon. The 50% correlation scale of coho salmon is also substantially smaller than those reported for upwelling indices and sea surface temperature. There are also periods of 5–10 years with high covariability between adjacent regions on the scale of hundreds of km, which may be of biological and physical significance.
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