Variation of Morphology among Juvenile Chinook Salmon of Hatchery, Hybrid, and Wild Origin

Abstract

Body morphology differed significantly between juvenile hatchery Chinook salmon Oncorhynchus tshawytscha that have experienced five generations of hatchery culture and juveniles derived from the wild founding stock and cultured in the same environment. All lines tested were raised in a similar hatchery environment. Thin‐plate spline analysis was used to characterize the morphometric variation among these lines of fish. Hatchery fish had a more compressed body, a narrower head, shorter maxillae, and a longer and narrower caudal peduncle than wild fish. Canonical discriminant analysis was able to correctly classify 88% of hatchery fish and 90% of wild fish. Second‐generation hybrids of the two lines were morphologically intermediate to but significantly different from both the hatchery and wild lines, and they appeared to be more similar to the wild line. These results suggest that the differences observed between lines are largely genetic in origin and may be a result of the divergence of the hatchery stock from the founding wild stock. In addition, family of origin had a significant effect on body morphology.

Morphological variability among three geographically distinct Arctic charr (Salvelinus alpinus L.) populations reared in a common hatchery environment

“…Both the genetic and environmental components can be involved in morphological differences between hatchery and wild stocks (Swain et al 1991;Wessel et al 2006), and the degree of divergence from the wild state is determined by both the proportion of an individual's life spent in hatchery and the number of hatchery generations . Nevertheless, a homogenous environment may generate partly reversed, convergent effects because of strong adaptive responses of salmonid to altered selection pressures ).…”

Rapid morphological divergence of cultured cod of the northwest Atlantic from their source population

“…It is possible that the smaller fins of the cultured cod resulted in part from a plastic response to water current. Studies in salmonids have shown that lower current velocity and variability experienced in culture can lead to relatively smaller fins (Pakkasmaa & Piironen 2000, Wessel et al 2006, Keeley et al 2007. Similarly, when compared to wild fish, farmed cod likely experience similar reductions in water velocity, and hence similar plastic effects on fin size could be expected in our study.…”

Morphological Differences Between Adult Wild and First‐Generation Hatchery Upper Yakima River Spring Chinook Salmon

“…Two basic patterns have been seen in hatchery fish, depending on the type of hatchery environment. ''Farmed'' fish (fish that are reared to adulthood in captivity) tend to be deeper bodied than wild fish (Webb et al 1991;Hard et al 2000), but ''sea-ranched'' fish (hatchery fish that are released as juveniles into the natural environment) tend to display the more streamlined phenotype typical of fish better adapted for sustained swimming (Taylor 1986;Fleming and Gross 1989;Swain et al 1991;Wessel et al 2006). Hatchery fish, both farmed and sea ranched, also show reduced snout development and important secondary sexual characteristics (Fleming and Gross 1989;Petersson and Jarvi 1993;Hard et al 2000).…”

“…More studies of morphological change, as well as domestication in general, need to be done on fish with the same genetic background. The morphological studies of and Wessel et al (2006) have done this, but in populations with substantial cultural histories. No study to date has addressed the development of morphological change as domestication proceeds in a previously wild population.…”