Genetic parameters and response to selection of harvest body weight of the Chinese shrimp Fenneropenaeus chinensis after five generations of multi-trait selection

Abstract

Genetic parameters and predicted and realized selection responses were estimated for harvest body weight of Chinese shrimp (Fenneropenaeus chinensis) after five generations of multi-trait selection. The body weights of 15,201 tagged shrimp representing 460 full-sib families in 6 generations were recorded at harvest. Heritability estimates for body weight showed large variation in magnitude (0.00±0.00-0.36±0.07) when analyzing data from each generation separately. When data from all generations (G0-G5) were included in analysis, the heritability estimate for body weight was 0.18. While, G0 was more affected by environmental conditions than the other generation in this study, when data from G0 was excluded, the heritability was 0.21. The common environment effect estimate was 0.08 when all data included and 0.06 when G1-G5 included. The females were significantly larger than the males at harvest (P<0.05). The genetic correlation of the harvest body weight between sexes was similar within and across generations, indicating that body weight in male and female shrimp is likely controlled by the same genes. Breeding candidates in the base population (G0) were selected according to their individual breeding values for growth. In later generations (G1-G5), candidates were selected according to a selection index including breeding values for growth, survival time after WSSV infection and pond survival. The response to selection for harvest body weight was estimated by two methods (the realized and predicted responses). The realized response was estimated from the differences in the least square means of body weight between the selection and control populations. The predicted response was obtained from the differences in the mean breeding values between generations. The accumulated realized response was 18.60% after performing five selections. The accumulated predicted responses estimated using two sets of genetic parameters obtained from within and across generation datasets were 6.43% and 6.50%, respectively. The results are discussed in a practical context of developing selective breeding programs for Chinese shrimp, and it is indicated that the selective breeding program has generated effective genetic improvement after five generations of selection. The future direction of the genetic improvement program is discussed. Statement of relevanceChinese shrimp, Fenneropenaeus chinensis, is one of the most valuable mariculture species in China. The Yellow Sea Fisheries Research Institute (Qingdao, China) initiated a multi-trait selective breeding program for Chinese shrimp in 2004, based on a combined family and within (inter) family selection scheme to improve growth, survival time after WSSV infection and pond survival. A new selected breed named “Huanghai No. 2” (registration no. GS01-002-2008) was approved in 2008. This program provided significant economic and social benefits. However, only limited results regarding this program have been reported, which involved genetic parameters of harvest body weight and genetic correlations among different traits using only one year data, a smaller subset of the current study.Growth is one of the most desirable economic traits in aquaculture. Good growth is important for efficient production and contributes to more profitable and sustainable development. Currently, the selective breeding program for F. chinensis is ongoing and the breeding nucleus was divided into different lines after performing five selections. In this paper, we will focus on the results related to genetic evaluation for the harvest body weights from G0 to G5. We will present more reliable estimates of phenotypic and genetic parameters, calculate the response to selection after performing five selections and discuss the longer term implications of the findings from a genetic improvement viewpoint.