Selection experiments for improving “pan-size” body weight of rainbow trout ( Oncorhynchus mykiss)

Abstract

Two generation selection experiments for improving pan-size body weight of rainbow trout were carried out in a series of four experiments including spring and autumn spawners. Each selection experiment consisted of a selection and a contemporary control line. Combined family selection was applied in all selection lines using pan-size body weight as the selection criterion. Comparisons of growth performance of selection and control lines included fattening of fish at two stocking densities. In general, responses under low density conditions were higher than those under high density conditions. After two generations, the highest significant response was obtained in line 4 with 32 g (deviation from control mean) or 27% at low density whereas at high density the response was only onefourth of this value. Averaged over all lines, realized heritability was 0.15. In general, positively correlated responses were found for rearing weight; however, greater changes in the ranking between rearing and fattening weight could be observed for a number of families. Till now, selection for fattening weight has not resulted in changes in the proportional weight of head and fins and has not altered carcass composition.