Mixed model estmation of genetic and environmental correlations in red swamp crawfish Procambarus clarkii (Girard)

Abstract

Total length, total weight, carapace length, carapace width, abdomen width, abdomen depth, chela length, chela width, abdomen meat weight and dressout percentage were measured on 752 individual crawfish Procambarus clarkii (Girard) from 39 full-sib families nested within 15 half-sib families. A nested mixed model analysis of variance and covariance was performed on all traits to obtain Henderson's method III variance and covariance components, as well as best linear unbiased estimators of the fixed effects of sex and male state of maturity. Genetic and environmental correlations were derived from mixed model variance and covariance components. Positive sire-based genetic correlations suggest that genetic gains in growth and processing yields, the major components of value of harvestable P. clarkii, may be pursued simultaneously in future breeding programmes. Data suggest that easily obtained external measurements are sufficiently correlated with growth and processing traits to allow for identification of potentially superior broodstock. Female, mature male and immature male levels of fixed effects, as well as estimated heritabilities for individual growth, body size and processing traits, were consistent with previous studies, further reinforcing the validity of data developed to date for use in planning P. clarkii breeding programmes.