Research Document 2018/042
Effects of Three Generations of Captive Breeding and Rearing on Survival, Growth, and Other Phenotypic Traits in Inner Bay of Fundy Atlantic Salmon (Salmo salar)
By Harvie, C., McWilliam, S., and O’Reilly, P.T.
Abstract
Live Gene Bank populations of Stewiacke River and Big Salmon River inner Bay of Fundy Atlantic Salmon (Salmo salar) have now undergone approximately three generations of captive breeding and rearing. Several characteristics of the Stewiacke Live Gene Bank program, including the maintenance of pedigree and other information on nearly all salmon spawned each year, make possible the monitoring of several key traits through time and the testing of some of the possible effects of the general Live Gene Bank program (and specific management strategies employed within), on several indicators of offspring performance.
A moderate amount of intra-year (or intra-generation) variation was observed for nearly all of the approximately 15 traits studied, and differences between years were often significant. The timing of some of the larger among-year differences observed often overlapped with either changes in measurement methodologies used or captive rearing conditions employed. However, we observed very few trends or directional changes in measured traits, potentially indicative of either plastic responses to directional environmental (captive or wild) changes through time or adaptation to captive conditions.
Our assessment of the overall general impact of the Live Gene Bank program on possible indicators of fitness was limited to testing for differences in performance traits across salmon that had experienced between 2.0 and 3.25 ancestral generations of captive breeding and rearing. Even so, survival in the wild from release at Age 0+ to recapture at Age 1+ appeared to decrease with increasing numbers of program generations, and this relationship was significant in one of four spawning years assessed. Results of investigations into some of the possible effects of individual variables, each associated with specific management strategies employed, on different metrics of offspring performance were mixed. Parental and maternal early juvenile rearing environments did not appear to influence offspring survival in the wild from release at Age 0+ to recapture at Age 1+ or Age 2+, approximately 15 and 27 months later, respectively, but it did appear to impact size (length and weight) of Age 1+ parr in the wild. We did not detect any effect of (1) parent family size in the wild, (2) parent Mean Kinship, (3) pedigree inbreeding (F), or (4) offspring expected heterozygosity, on any offspring performance trait measured. Female (but not male) parent age did have a significant (positive) impact on nearly all metrics of offspring performance assessed, and only some of this effect appears to be due to increasing egg size.
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