Heritabilities and genetic correlations of size traits at harvest size in sexually dimorphic Pacific white shrimp (Litopenaeus vannamei) grown in two environments

A captive population of Pacific white shrimp (Penaeus vannamei) replicated in two environments was evaluated for genetic variability and covariability of size traits. A total of 37 full-sib families, each with an average of 16-20 individuals within family, were used for the analysis. There was no family by environment interaction for any of the traits. However, both fixed effects, sex and environment, were significant. The shrimp grown in environment 'B' (Sinaloa) grew larger and heavier than those grown in environment A (La Paz), possibly because of the higher temperatures and lower densities in the first one during grow-out. The females were significantly larger than the males for all traits, except for abdominal (tail) length and weight. The heritabilities, estimated through MTDFREML (multiple-trait derivative-free restricted maximum likelihood) after introducing environment and sex as fixed effects, were total length 0.22 +/- 0.07, abdominal length 0.23 +/- 0.07, cephalothorax length 0.17 +/- 0.06, total weight 0.17 +/- 0.06, abdominal weight 0.18 +/- 0.06, cephalothorax weight 0.15 +/- 0.06, and width of the first abdominal segment (0.14 +/- 0.05). Genetic correlations (r(g)) were high between the length and weight (total and abdominal), but lower for cephalothorax weight or length with the other traits. The width of the first abdominal segment correlations with other traits was intermediate.