Evaluation of genetic parameters for reproductive traits and growth rate in the Pacific white shrimp Litopenaeus vannamei reared in brackish water

Abstract

It is very common to culture L. vannamei in brackish water or under low salinity conditions, but brackish water or low salinity genetic breeding for broodstock shrimp have not yet been studied. This study provides a preliminary evaluation of feasibility of broodstock shrimp genetic selection in brackish water. Shrimps were initially reared at brackish water (10 ppt) eight months, and female and male shrimps were selected from each family for reproductive traits test at the salinity of 30 ppt. The heritability and genetic correlations among growth rate and reproductive traits can have important implications to the design of breeding programmes to enhance the growth rate and reproductive efficiency. However, there are no reports on the relationship between growth rate and fecundity in shrimps reared eight months in brackish water. The principal objective of the present study was to estimate the genetic parameters concerning the growth rate and reproductive traits using a restricted maximum likelihood (REML) approach based on a univariate or multivariate animal model. The goal was to confirm the genetic relationship between growth rate and fecundity in Litopenaeus vannamei under the brackish water selection about eight months. In this study, the growth and reproduction traits of 115 L. vannamei families were tested when they were cultured until 11 months. The traits of the body weight at 2 months (M2BW), body weight at 4 months (M4BW), body weight at 8 months (M8BW), growth rate before 4 months (G1R), growth rate between 8 and 11 months (G2R), first spawning age (FSA), egg-laying frequency (ELF), average spawning interval (ASI), and body weight after testing (11 months, M11BW) were collected. The heritability levels of the G2R, ELF, and ASI were 0.03 ± 0.03, 0.074 ± 0.02, and 0.10 ± 0.03, respectively, which are low heritability levels. The heritability levels of the G1R, FSA, M8BW, and M11BW were 0.53 ± 0.06, 0.92 ± 0.08, 0.58 ± 0.08, and 0.52 ± 0.08, respectively, which are high heritability levels. The genetic correlations between M8BW and M11BW, between G2R and ASI, between M8BW and FSA, and between M11BW and FSA were 0.99 ± 0.01, 0.93 ± 0.10, 0.64 ± 0.10, and 0.67 ± 0.10, respectively, which are medium-high correlations; the genetic correlations between M11BW and ASI, between M8BW and ASI, and between G1R and ASI were − 0.04 ± 0.21, −0.20 ± 0.19, and − 0.30 ± 0.18, respectively, which are negative correlations. The genetic relationship between the growth rate and reproductive traits was different according to the growth stage. In the early growth stage of L. vannamei, early growth rate and reproductive were not trade-offs, but there is a clear trade-off between growth rate and reproductive at breeding season. The estimates of the genetic parameters indicate that these traits can be subjected to selection in the brackish water to improve reproductive efficiency in females. The genetic breeding programme according to the growth rate from 0 to 4 months is not associated with a negative selection for reproductive traits.