Genetic parameter estimation for juvenile growth and upper thermal tolerance in turbot (Scophthalmus maximus Linnaeus)

Twenty-six half-sib groups (53 full-sib families) of turbot, Scophthalmus maximus Linnaeus, were obtained by artificial insemination. We measured growth in the offspring (40-50 individuals/family) and subjected them to a thermal tolerance challenge over a period of 34 d. There was no significant difference in daily mortality (range: 0.580%-1.391%) between Days 1-13 during the thermal tolerance challenge. However, daily cumulative mortality increased rapidly between Days 14 and 29, especially on Days 15 and 16 (20.232% and 34.377%, respectively). Mortality was highest on Day 16 (14.145%). We estimated the genetic parameters using the average information restricted maximum likelihood method. We used a likelihood ratio test to evaluate the significance of effects in models with and without identity as an effect, and compared the final log-likelihoods (maximum log L). Lastly, we estimated phenotypic and genetic correlation between the upper thermal tolerance limit (UTT) and body weight (BW). In this study, the positive phenotypic correlation was low between UTT and BW (0.093 +/- 0.029). The genetic correlation between UTT and BW was negative (-0.044 +/- 0.239). The heritability for upper thermal tolerance was low (0.087 +/- 0.032), which is of approximately moderate heritability. The heritability for body weight was high (0.303 +/- 0.074). Our results suggest there is significant potential for improvement in the culture of turbot by selective breeding.