| Abstrakt: |
Using indices of survival rate (residuals from stock-recruitment relationships) across four decades, we examined the spatial patterns of covariation among 40 wild and 27 hatchery stocks of chum salmon from 15 geographical regions in Washington, British Columbia, and Alaska. We found strong evidence of positive covariation among spawner-to-recruit survival rates of wild stocks within regions and between certain adjacent regions (e.g., correlations from 0.3 to 0.7) but little evidence of covariation between stocks of distant regions (e.g., separated by 1,000 km or more). Similarly, for hatchery stocks from Washington, British Columbia, and southeast Alaska, positive covariation in the indices of fry-to-recruit survival rate occurred only within regions and between certain adjacent regions. These patterns suggest that important environmental processes affecting interannual variation in spawner-to-recruit survival rates of chum salmon operate at local or regional spatial scales rather than at the larger, ocean-basin scale. These results are similar to our previous findings for sockeye salmon and pink salmon and help identify the spatial characteristics of environmental variables required to improve forecasting models and better understand the effects of climatic changes on salmon productivity. Our finding that local or regional-scale processes primarily affect productivity differs from that of other studies, which suggest that large, ocean-basin-scale processes predominate. However, the latter studies were mostly based on time series of aggregate catch data, which provide limited spatial resolution and are potentially confounded by several factors. [ABSTRACT FROM AUTHOR] |
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