Effect of stocking density on mortality rate, physiological status and nutrient contents of Chinese mitten crab Eriocheir sinensis during overwintering cultivation

Abstract

The Chinese mitten crab, Eriocheir sinensis (H. Milne Edwards), is an important economic aquaculture species in China. It is very popular within Chinese consumers for the abundant nutrition and delicious taste. It has been widely cultured and had great yield recently; yet, the short available time of E. sinensis cannot satisfy consumers’ increasing demanding. Thus the overwintering cultivation of E. sinensis has become one problem to urgently await development. Aiming to find the optimal stocking density and time for overwintering rearing E. sinensis using net cages embedded in a circulating pond aquaculture system, in the present study, we analyzed the variations in growth performance, death rate, physiological status, and nutrient contents of E. sinensis at different stocking densities over time periods. The death rate increased significantly after rearing for 90 days, while medium stocking density had a slight advantage than other densities. Interestingly, E. sinensis had no significant weight loss during overwintering period regardless of stocking densities. Our findings suggested that the optimal stocking density is around 21.88 kg/m2 in case of overwintering cultivation less than 90 days; while a medium density of 15.63 kg/m2 is more suitable for longer term overwintering cultivation (more than 90 days). In any case, the optimal overwintering rearing of E. sinensis should not beyond the 2rd, April. We can barely found difference caused by stocking density in activity of digestive enzymes, antioxidant status, or gene expression of hsp70; however, their levels were fluctuant over rearing time. Moreover, we found no significant variation in muscular amino acids composition, but a rising ratio of PUFA/SFA, as well as increased levels of C20:4 and C20:5 in edible tissues after 105-days overwintering cultivation, suggesting an improved nutritional value and eating quality of E. sinensis. Our results provide a reference standard for the overwintering cultivation of E. sinensis.