First genetic evaluation of growth traits in Larimichthys polyactis to guide the formulation of selective breeding programs

Growth is an economically important trait in aquaculture. For the genetic improvement of growth traits in Larimichthys polyactis, a relatively new aquaculture species with great potential in large-scale farming, a genetic evaluation of these traits is necessary. In the present study, 34 families of L. polyactis were used to estimate genetic parameters for body weight, total length, and body length at the age of 11 months. Heritability estimates for the three growth traits including body weight, total length, and body length were 0.17 +/- 0.06 to 0.23 +/- 0.07 and were significantly different from zero (P < 0.05). The genetic correlation coefficients among the three traits were highly positive (i.e., 0.88-0.96). A selection ratio of 30% can result in an expected genetic gain (delta G) of 3.41% and relative genetic gain (delta G') of 5.31% per generation for body weight in L. polyactis. There were significant differences in the response to selection when using parents selected by estimated breeding values (EBVs) and by phenotypic values (PVs). The concordance rate of individuals selected by the two methods was only 42.72%-46.02%. The average breeding value of the individuals selected based on EBVs (6.87 for body weight) was much higher than that for individuals selected based on PVs (3.48 for body weight). Environmental factors had a substantial impact on the growth phenotype of L. polyactis; accordingly, the EBV selection method is more efficient than the PVs method for breeding. The results of this study confirm that L. polyactis shows genetic variation for growth traits and highlight the enormous potential for improvements in growth by selective breeding based on EBVs.