Straying of hatchery salmon in Prince William Sound, Alaska

Richard E Brenner,William S Grant,Steve D Moffitt

doi:10.1007/s10641-012-9975-7

Richard E Brenner, William S Grant + Show 1 more

Open Access

https://doi.org/10.1007/s10641-012-9975-7

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Abstract

The straying of hatchery salmon may harm wild salmon populations through a variety of ecological and genetic mechanisms. Surveys of pink (Oncorhynchus gorbuscha), chum (O. keta) and sockeye (O. nerka) salmon in wild salmon spawning locations in Prince William Sound (PWS), Alaska since 1997 show a wide range of hatchery straying. The analysis of thermally marked otoliths collected from carcasses indicate that 0–98% of pink salmon, 0–63% of chum salmon and 0–93% of sockeye salmon in spawning areas are hatchery fish, producing an unknown number of hatchery-wild hybrids. Most spawning locations sampled (77%) had hatchery pink salmon from three or more hatcheries, and 51% had annual escapements consisting of more than 10% hatchery pink salmon during at least one of the years surveyed. An exponential decay model of the percentage of hatchery pink salmon strays with distance from hatcheries indicated that streams throughout PWS contain more than 10% hatchery pink salmon. The prevalence of hatchery pink salmon strays in streams increased throughout the spawning season, while the prevalence of hatchery chum salmon decreased. The level of hatchery salmon strays in many areas of PWS are beyond all proposed thresholds (2–10%), which confounds wild salmon escapement goals and may harm the productivity, genetic diversity and fitness of wild salmon in this region

Highlights

Pacific salmon (Oncorhynchus spp.) are noted for their abilities to home to natal areas to spawn
Streams closest to release facilities generally contained the highest proportions of hatchery pink salmon strays (Joyce and Evans 1999)
The results of this study show large amounts of hatchery salmon straying in some areas in Prince William Sound (PWS)

Summary

Introduction

Pacific salmon (Oncorhynchus spp.) are noted for their abilities to home to natal areas to spawn. This homing isolates populations from one another and often leads to adaptations to the environmental conditions of a particular watershed (e.g., Quinn 1993, 2005; Eliason et al 2011). Some wild fish stray into non-natal spawning areas. These background levels of natural straying may be adaptive by allowing populations to expand into new habitats and by supplementing populations with low genetic diversities (Quinn 2005). Hybridizations between hatchery and wild fish may decrease the adaptive fitness of wild populations (McClelland et al 2005; Ford et al 2006; Wessel et al 2006)

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