A test of genetic adaptation to captivity in diet after one generation

Supervisor: Dylan Fraser (Concordia University, Biology Department, Montreal, QC, Canada)
The central premise of this study is that (i) genetic adaptation to captivity can arise even after a single generation; (ii) the extent of this adaptation might differ among populations given that populations are rarely coming into captivity from the same starting point in their genetic/phenotypic characteristics, and that (iii) such adaptation may be most likely to occur at life stages which naturally experience high levels of mortality in nature. In highly fecund fishes, such as salmonids, natural and captive mortality is often highest in the first few months of exogenous feeding. We hypothesized that this might render salmonids particularly susceptible to genetic adaptation to captivity in relation to diet changes. Wild fish normally feed on live prey whereas they are fed pellet feed in captivity: fish that do not adopt pellet feed well under captive conditions experience reduced growth and/or die. We tested this hypothesis by generating a large number of families from F1 captive and wild fish originating from the same three populations and then rearing them each on pellet and live feed for three months at the beginning of exogenous feeding. This study has suggested that captive fish of every population grew disproportionately better than wild fish on pellet than artemia feed, with one wild population (WN) growing more poorly on pellets than artemia. In terms of mass, all captives were larger than their wild counterparts in all populations and the mass of all artemia fed fishes were smaller than pellet fed fishes, irrespective of source. There was no difference in mortality between captive and wild fishes (only 10% mortality in both cases), regardless of diet. Thus, our current findings suggest that there would be phenotypic difference between captive and wild individuals to captivity in diet changes after one generation.

Keywords: Genetic adaptation, captivity, exogenous feeding, growth, mortality etc.