Heterosis in growth and low temperature tolerance in Jinhu grouper (Epinephelus fuscoguttatus ♀ × Epinephelus tukula ♂)

Hybridization is a widely used and effective method in grouper breeding. In this study, we constructed full-sib families of brown-marbled grouper (Epinephelus fuscoguttatus), Jinhu grouper (E. fuscoguttatus ♀ × E. tukula ♂), and Hulong grouper (E. fuscoguttatus ♀ × E. lanceolatus ♂) and compared the growth characteristics under industrial conditions. The body weight of Jinhu grouper was 1.49 times that of Hulong grouper (P < 0.05) and the body weight of Jinhu grouper was 2.03 times that of E. fuscoguttatus (P < 0.05). Moreover, the survival rate of Jinhu grouper was significantly higher than those of Hulong grouper and E. fuscoguttatus (P < 0.05). The relationships between body length and body weight (W = aLb) in Jinhu grouper, Hulong grouper, and E. fuscoguttatus were similar, and both Jinhu grouper and Hulong grouper may inherit the growth pattern of E. fuscoguttatus. The b values were all <3, indicating allometric relationships at this stage. In a comparison of the low temperature tolerance, E. fuscoguttatus and Jinhu grouper stopped feeding at 19 °C and 16 °C, respectively, and 11 °C and 9 °C were the half-lethal temperatures, respectively. A histopathological analysis showed that the degree of damage in the gill, muscle, and liver tissues increased as the temperature decreased. The activities of total superoxide dismutase (T-SOD), total antioxidant capacity (T-AOC), and glutathione peroxidase (GSH-Px) in the liver decreased initially and then increased as the temperature decreased. The malondialdehyde (MDA) contents in the liver increased initially and decreased thereafter. Lysozyme (LZM) activity in the serum increased initially and then decreased, and immunoglobulin M (IgM) levels did not vary significantly with respect to temperature (P > 0.05). In conclusion, Jinhu grouper was characterized by a rapid growth rate, high survival rate, and low temperature resistance. This hybrid grouper is suitable for industrial culture in China, with broad potential applications