Size and condition of wild and hatchery pink salmon juveniles in Prince William Sound, Alaska

摘要

Declining wild stocks and reduced body size of pink salmon Oncorhynchus gorbuscha in Prince William Sound have led to the hypothesis that the carrying capacity of the sound, and possibly that of the Gulf of Alaska, for salmon has been reached. We compared the length, weight, and energetic content of juvenile pink salmon (1) among different stations, (2) between one hatchery group and wild pink salmon from several stations, and (3) among several hatchery release groups and wild pink salmon from two stations in the sound using analysis of variance. There were significant differences in the lengths of fish among stations but no geographic pattern. Pink salmon at two nearby stations in southwestern Prince William Sound were the smallest (71.5 mm in Whale Bay) and largest (92.4 mm in Bainbridge Passage) of the six stations sampled. There were also differences in size among the hatchery and wild groups. Wild fish were consistently larger than the most abundant hatchery group (Cannery Creek). Within central Prince William Sound, Cannery Creek Hatchery pink salmon were significantly shorter than other hatchery release groups and wild salmon. Size variation was probably dependent on size upon entry and time of entry into marine waters. The energy content of juvenile pink salmon did not differ significantly between wild and hatchery fish but did vary among stations, albeit with no geographic pattern. Hatchery fish west of Naked Island had significantly higher energy content than those east of Naked Island. The consistencies in energy content among groups of fish from the same geographic area suggest that processes occurring on local scales (e.g., the effect of stratification on secondary production and local depletion by planktivores) are important in determining the condition of juvenile pink salmon.