Heritability of Cold Tolerance in Red Drum

Abstract

AbstractHeritability (h 2) of cold tolerance was estimated for red drum Sciaenops ocellatus, an economically important sciaenid fish in the southern USA. Nineteen families were generated via environmentally induced spawning of multiple sets of five broodfish (three dams × two sires) and were mixed in three common‐garden replicate tanks for cold tolerance challenge. All offspring were assigned postmortem to parents based on genotypes at nuclear‐encoded microsatellites. The cold tolerance trial was initiated when offspring were 230–251 d old (total length mean ± SD = 182 ± 26 mm). Temperature was decreased progressively from 25°C to 3°C over a 30‐d period and was maintained at an average of 3.1°C until all fish expired. Mortality began when temperature reached 5°C. Cold tolerance of individual fish was quantified based on survival time and a cooling‐degree‐hours (CDH) index. The h 2of cold tolerance was estimated using an animal mixed model and a restricted maximum likelihood algorithm. The h 2 (mean ± SE) estimate was 0.32 ± 0.12 and indicated a significant genetic component to cold tolerance in red drum. Phenotypic correlations between cold tolerance and body weight or length were positive but low (0.18 and 0.23, respectively), suggesting that selective breeding for increased growth rate in red drum would not have a negative impact on cold tolerance in the selected strain.