Body traits in rainbow trout: II. Estimates of heritabilities and of phenotypic and genetic correlations

Abstract

Genetic parameters were estimated from data recorded at slaughter on 2–4-kg rainbow trout ( Salmo gairdneri) from three year-classes. Observations were made on 4466 fish of 47 sires and 249 dams nested within sires (data set I). Some traits were recorded only on a sample of 662 fish of 37 sires and 111 dams included in data set I (data set II). No sire or dam was used in more than one year-class. Heritabilities based on the sire component of variance for traits in data set I were 0.21 for ungutted and gutted body weight, 0.18 for body length, 0.36 for dressing percentage, 0.19 for condition factor, 0.23 for gonad weight, 0.32 for belly thickness score and 0.40 for belly thickness measured, 0.25 for abdominal fat score and 0.28 for viscera weight, and 0.27 for meat colour score. Heritabilities for traits in data set II were 0.22–0.30 for body circumference, 0.19–0.34 for size and belly thickness measurements of the cross sections at the pelvic and dorsal fins, 0.13–0.25 for body shape, 0.00–0.31 for shape of the cross sections and 0.33, 0.47 and 0.03 for percent water, fat and protein in the meat, respectively. Genetic correlations of body weight with (a) body circumference traits and size measurements of the cross sections were all very high; (b) belly thickness, condition factor, abdominal fat score and meat colour score were low, but positive; (c) fat percentage was also low, but negative. Genetic correlations of belly thickness with abdominal fat score and fat percentage were −0.54 and 0.24, respectively, and −0.33 between fat percentage and abdominal fat score. Genetic correlations of condition factor with carcass fat percentage and body shape were 0.15 and 0.52, respectively, and the phenotypic correlations were 0.16 and 0.82, respectively. It was concluded that condition factor is an adequate measure of body shape. In conclusion, the possibilities for genetic improvement of body weight, belly thickness, body shape, abdominal fat, fat in the meat and meat colour are very good in rainbow trout. No strong unfavourable genetic correlation was found among the traits.