Predicting selection response for growth of channel catfish

Estimates of heritability, phenotypic and genetic correlations were obtained for body length and weight at 5 months and body length and weight at 15 months in channel catfish. The estimates were obtained from a half-sib analysis by mating 20 males to two females each, producing 20 half-sib and 40 full-sib progeny families. Mortality of fish during the study reduced the number of families to 17 half-sib and 34 full-sib. Comparisons of selection methods were made for body length at 5 months and body weight at 15 months. The results of the study show: 1) heritability estimates for body length and weight at 5 months was 0.12 and 0.61, respectively, and body length and weight at 15 months was 0.67 and 0.75, respectively; 2) from the magnitude of the estimates of heritability, it can be inferred that large amounts of additive genetic variance exist in three of the traits (length at 5 months and length and weight at 15 months) and that selection for these traits should be successful; 3) estimates of phenotypic correlation among the four traits ranged from 0.90 to 0.30, and genotypic correlation among the four traits ranged from 1.47 to 0.71; 4) the magnitude and positive nature of the genetic correlations indicated that simultaneous selection for the four traits in channel catfish would be effective; and 5) comparisons of predicted response under individual, indirect and index selection, show that selection on an index based on all four traits gives maximum response in length at 5 months and weight at 15 months.