Family × Environment interactions in the growth and survival of Arctic charr (Salvelinus alpinus) grown in brackish and fresh water

We investigated whether Fraser strain Arctic charr Salvelinus alpinus L. reared in fresh water (FW) differed in survival and growth from full siblings transferred to brackish water (BW) and whether family performance was consistent throughout 1 year of commercial growth. Fish were grown communally (n = 3600) in either FW or BW from May 2008 to May 2009. Mean family survival in BW was moderately correlated with mean family survival in FW (r = 0.342; P = 0.032). Fish which survived until the conclusion of the experiment were significantly heavier in body weight at the baseline assessment than their full-sibs which died. Family by treatment interactions were detected for body weight, condition factor and specific growth across all measurement dates (May 2008, October 2008 and May 2009) and growth intervals. Despite the varied response of families to treatment, mean family body weight in FW was correlated phenotypically with BW body weight in October 2008 (r = 0.633, P < 0.0001) and marginally correlated in May 2009 (r = 0.289, P = 0.061). These data suggest that body weight in FW and body weight in BW should be analysed as separate, but correlated traits in Arctic charr breeding programs.