Variation of growth traits at different generations of Pacific white shrimp (Litopenaeus vannamei)

Variation of growth traits of body length and body weight was investigated in seven cultured stotcks of four generations of Pacific white shrimp (Litopenaeus vannamei), including Hainan stock (first generation of imported prawns, G1), Shandong and Raoping stocks (G2), Zhanjiang 2 and Zhanjiang 3 stocks (G3), Zhanjiang 1 and Shanghai stocks (G4).The average body lengths (ranges) were 14.76 (13.25~15.99), 8.46 (6.28~10.48), 9.24 (4.28~10.70), 7.75 (5.13~9.36), 11.38 (8.13~14.12), 5.25 (3.47~6.83) and 7.14 (4.14~9.00) in the seven stocks, respectively, and the coefficients of variances (CVs) of body length were 0.04, 0.08, 0.08, 0.09, 0.12, 0.14 and 0.14, respectively. The average body weights (ranges) were 33.41 (24.33~39.74), 5.19 (1.80~9.68), 6.95 (3.18~11.34), 4.62 (1.52~9.87), 15.03 (6.00~26.96), 1.47 (0.48~3.42) and 3.29 (0.49~6.20), respectively, and the CVs of body weight were 0.10, 0.23, 0.21, 0.27, 0.32, 0.39 and 0.36, respectively. The CVs of body length and body weight increased from generation to generation, and nearly 10% increment per generation was showed in the CVs of body weight. The CV of the first generation was similar to that of parental stock selected in USA. The correlation coefficient between body length and body weight was significant in each stock (P < 0.01). The regression equation of body weight and body length was W=0.01L^2.93 based on all individuals. This study suggested that divergence of growth traits in Pacific white shrimp imported from USA have occurred from generation to generation.