Insights into the genetic covariation between harvest survival and growth rate in olive flounder (Paralichthys olivaceus) under commercial production environment

In aquaculture, selective breeding for survival till harvest have become an alternative strategy for improving disease resistance and production. However, knowledge of genetic parameters of harvest survival, e.g., heritability and genetic correlations between survival and growth rate traits, is still scarce. The aims of this study were to estimate genetic parameters for harvest survival and growth rate traits under commercial farming conditions in olive flounder (Paralichthys olivaceus). Harvest survival was defined as a binary trait; growth traits were measured as average daily gain (ADG), specific growth rate (SGR), daily growth coefficient (DGC) and body weight (BW). Data from a population of 241 full-sib families (involving 39,904 individuals, four generations) were used. Heritabilities of survival were low but significant, which were 0.15 ± 0.04 and 0.22 ± 0.01 on observed and underlying scale, respectively. Heritability estimates for ADG, SGR and DGC were medium to high, which were 0.33 ± 0.06, 0.83 ± 0.07, 0.58 ± 0.07, respectively. While the heritability of BW is of low magnitude (0.17 ± 0.08). The genetic correlations between harvest survival and three growth rate traits (i.e., ADG, SGR and DGC) were very strong (ranging from 0.66 to 0.79), which is an exciting result. However, the genetic correlation between harvest survival and BW was much lower (0.17 ± 0.08). These results suggest that selection for harvest survival would consequentially result in concomitant increase of growth rate, and vice versa. Our findings revealed novel insights into the genetic improvement of growth rate and harvest survival through genetic selection in olive flounder.