Preliminary study on the suitable stocking density of Chinese mitten crab （Eriocheir sinensis） under rice-crab co-culture system in the saline-alkaline area of the Yellow River Estuary

Abstract:

A 180-day rice-crab co-culture experimental trial （female crab:male crab=1:1） was conducted in the saline-alkaline area of the Yellow River Estuary to find the suitable stocking density of Chinese mitten crab （Eriocheir sinensis）. The effects of different stocking densities （1.50 ind./m²， 0.75 ind./m² and 0.38 ind./m²， indicated as D150， D075 and D038 groups， respectively） on the growth and culture performance， edible tissue indices， proximate composition， physiological metabolism， contribution of food and economic performance of rice-crab were studied. The results showed that： （1） The weight gain rate （WGR）， specific growth rate （SGR） and survival rate （SR） of crab increased significantly with the decrease of stocking density， while the yield and feed conversion rate （FCR） decreased significantly. （2） There was no significant difference in edible tissue index and total edible rate among different stocking density groups， but the gonadosomatic index （GSI）， hepatosomatic index （HSI） and total edible yield （TEY） of female crab increased slightly with the decrease of stocking density. （3） With the decrease of stocking density， the contents of crude protein in muscle of females and males decreased significantly， while the contents of crude lipid in hepatopancreas of females increased significantly. （4） In terms of physiological metabolism indices， the activities of alkaline phosphatase （ALP） and acid phosphatase （ACP） in hepatopancreas of females increased significantly with the decrease of stocking density， while total antioxidant capacity （T-AOC） and the contents of malondialdehyde （MDA） in serum decreased significantly. Similarly， ALP activity in hepatopancreas of males was the highest in D038 group， while the contents of MDA in hepatopancreas and T-AOC in serum were decreased significantly and minimum value was found in D038 group. （5） The first food source of crabs under different stocking densities was formulated feed （39.39%-52.33%）. With the decrease of stocking density， the contribution of feed in food sources was increased， while the contribution of background crabs was decreased. （6） There was no significant difference in partial return and partial gross and the highest profit of each group， whilst the return-on-investment （ROI） of D038 group was significantly higher than that of other density groups. In summary， although the crabs in high-density group had the highest total yield and partial return， the crabs in low stocking density group achieved the best growth performance， health status， profit and ROI. Therefore， under the condition of this experiment， the suitable stocking density of crabs is 0.38 ind./m² under rice-crab co-culture system in the saline-alkaline area of the Yellow River Estuary.