Evaluation of culture and immunity performance of the second-year-old early-maturing and late-maturing strains of the fourth selective generation during the juvenile culture of Chinese mitten crab (Eriocheir sinensis)

When breeding for some specific parameters, relevant parameters always undergo covariation. A selective breeding program has been operated on Eriocheir sinensis for different mature time and culture performance equally since 2011, but crabseed quality of selected populations has not been evaluated yet. This study was aimed to evaluate the crabseed quality of two selected populations (early-maturing strain: EM, late-maturing strain: LM) compared to pond-reared crabseed without selection (control). The results showed that: ① The final weight and specific growth rate (SGR) of two selected populations were both relatively higher than those of the control all through the experiment, and the average weight of EM was lower than the LM between August and November, but no significant difference was observed. ② The order of survival rate and final yield was EM > LM > control with significant difference in yield of females, the order of precocious rate was opposite with significant difference in females as well. ③ As for the immune index, the levels of alkaline phosphatase (AKP), acid phosphatase (ACP) and total antioxidant capacity (T-AOC) in hepatopancreas and hemolymph of both selected populations were higher than the control, with significant difference of ALP level in hepatopancreas of females and significant difference of T-AOC level in hemolymph of males. ④ The injection of Aeromonas hydrophilia resulted in both lower (29.50% and 22.94%, respectively) cumulative mortalities of two selected populations. In conclusion, selection for different mature time and culture performance of E. sinensis also presented an effective improvement in their crabseed quality.