AEI 10:99-113 (2018)  -  DOI: https://doi.org/10.3354/aei00261

ABSTRACT: To assess the potential for introgression and competition between hatchery-produced (H_p) and natural-origin (N_o) chum salmon Oncorhynchus keta, we quantified a suite of fitness-related morphological and life-history traits on the spawning grounds of a small creek in Southeast Alaska that has high rates of immigration from nearby hatchery programs. Using thermally marked otoliths to distinguish between H_p and N_o fish, we estimated that 51.4% of individuals examined in 2015 were H_p strays. Compared with their N_o counterparts, H_p males and females entered the creek significantly later, were younger at maturity, smaller in body length, and smaller for a given age. On average, H_p females lived 2 d less on the spawning grounds than N_o females and also had higher rates of egg retention (47 vs. 19% observed in N_o females). The observed phenotypic differences between the local N_o and H_p individuals suggest barriers to introgression through combinations of selection against strays or spatio-temporal segregation on the spawning grounds, though the phenotypic baseline of the N_o population prior to potential hatchery influence is not known, nor is the extent to which environmental plasticity may be influencing trait expression. Although rates of interbreeding may be sufficiently low to currently maintain phenotypic differences between N_o and H_p strays, at least some spawning did occur by the majority of H_p individuals. Ultimately, it remains unclear how long the presumably adaptive phenotype of the N_o population may persist given the consistently large numbers of strays appearing annually on the spawning grounds.

KEY WORDS: Homing · Dispersal · Enhancement · Hatchery · Competition · Introgression · Local adaptation · Oncorhynchus keta

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Cite this article as: McConnell CJ, Westley PAH, McPhee MV (2018) Differences in fitness-associated traits between hatchery and wild chum salmon despite long-term immigration by strays. Aquacult Environ Interact 10:99-113. https://doi.org/10.3354/aei00261 Export citation Share:    Facebook - - linkedIn