Differences in Morphology between Wild and Hatchery Populations of Juvenile Coho Salmon

Abstract

To assess the degree of morphological divergence between wild and hatchery-reared juvenile coho salmon (Oncorhynchus kisutch), juveniles from five hatcheries and five wild populations in south-coastal British Columbia were studied. The morphology of hatchery coho salmon was significantly less variable than the morphology of wild-reared juveniles with respect to individual characteristics and overall body form. Populations that were close geographically tended to be similar morphologically in wild-wild and hatchery-hatchery comparisons, but not when wild and hatchery populations were compared together. A principal components analysis suggested a distinct grouping of juvenile coho salmon into hatchery and wild morphological types. Discriminant function analysis and jackknifed classification procedure indicated that juvenile coho salmon could be classified as either hatchery or wild in origin with over 90% accuracy. The morphological differences and the reduced variation of hatchery juveniles observed in this study probably result, in large part, from environmental differences and the greater homogeneity of hatchery environments compared to natural rivers and streams.