Life-long and transgenerational effects of early experience in Atlantic salmon (Salmo salar)

Abstract

Supportive-rearing programs to produce individuals for release in efforts to re-establish populations of threatened species continue to grow in number and scope. Based on the increasingly reported negative effects of captive exposure, we hypothesised that early captive exposure may affect fitness not only later in life but into the next generation, exactly when wild fitness must be present to contribute to sustainable population augmentation. We examined a supportive rearing program for endangered Atlantic Salmon (Salmo salar) that releases juvenile fish at two life stages (fry and parr) having varying duration of captive exposure. We followed multiple cohorts from release to the wild, collected 1-3 years later, held in a captive marine environment until maturity, and produced broods of offspring to examine effects of parental captive exposure on viability of the next generation. We found that the additional early-life captive exposure for parr resulted in smaller and younger smolts, adults, and smaller less viable offspring. Parr-origin fish survived better than fry from time of release until smolt stage as well as during captive marine rearing however, this is not likely indicative of improved wild fitness. We demonstrate how brief manipulations of early life exposure resulted in significant effects on fitness and present these findings in context of designing effective population recovery strategies.