Influence of breeding habitat on bear predation and age at maturity and sexual dimorphism of sockeye salmon populations
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Abstract
Age structure and morphology differ among Pacific salmon (Oncorhynchus spp.) populations. Sexual selection and reproductive capacity (fecundity and egg size) generally favor large (old), deep-bodied fish. We hypothesized that natural selection from physical access to spawning grounds and size-biased predation by bears, Ursus spp., opposes such large, deep-bodied salmon. Accordingly, size and shape of salmon should vary predictably among spawning habitats. We tested this hypothesis by measuring the age composition and body depth of sockeye salmon, Oncorhynchus nerka, and the intensity of predation in a range of breeding habitats in southwestern Alaska. Stream width was positively correlated with age at maturity and negatively correlated with predation level. However, salmon spawning on lake beaches were not consistently old, indicating that different factors affect age in riverine- and beach-spawning populations. Body depths of male and female salmon were positively correlated with water depth across all sites, as predicted. However, the mouths of some streams were so shallow that they might select against large or deep-bodied salmon, even in the absence of bear predation. Taken together, the results indicated that habitat has direct and indirect effects (via predation) on life history and morphology of mature salmon.
Study Area
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | Influence of breeding habitat on bear predation and age at maturity and sexual dimorphism of sockeye salmon populations |
| Series title | Canadian Journal of Zoology |
| DOI | 10.1139/z01-134 |
| Volume | 79 |
| Issue | 10 |
| Year Published | 2001 |
| Language | English |
| Publisher | NRC Research Press |
| Contributing office(s) | Western Fisheries Research Center |
| Description | 12 p. |
| First page | 1782 |
| Last page | 1793 |
| Country | United States |
| State | Alaska |
| Online Only (Y/N) | N |
| Additional Online Files (Y/N) | N |
| Google Analytic Metrics | Metrics page |