池塘放养密度对三疣梭子蟹生长、成活及养殖经济效益的影响

Effects of Stocking Density on Growth, Survival and Profitability of Portunus trituberculatus Reared in Commercial Earth Pond

在雌体放养密度分别为12 000只/hm^2(D1),19 500只/hm^2(D2),27 000只/hm^2(D3)的3个梯度下进行为期6个月的梭子蟹养殖试验,研究梭子蟹大规格蟹种在池塘养殖中的适宜放养密度。结果显示:(1)不同密度组梭子蟹的终末体质量、月增重率和特定生长率均较为接近,无显著差异(P>0.05);(2)成活率差异较大,D1组的成活率最高,达50%左右,显著高于D2组和D3组(P<0.05);(3)饵料系数表现出随着养殖密度的升高显著降低的趋势,即D3>D2>D1;(4)单位面积产量相近,但是高密度组因苗种和饲料成本增加,导致其净利润和回报率降低。综合认为,池塘养殖条件下梭子蟹雌体放苗密度为12 000只/hm^2为宜,过高的放养密度反而会加剧养殖成本,降低养殖经济效益。

Young Portunus trituberculatus were cultured at three stocking densities at 12 000（D1）, 19 500 （D2）, 27 000（D3） individuals per ha respectively for 6 months to test the optimal stocking density for female P. trituberculatus cultured in commercial earth pond in the present study. The results showed that： （1）There were no difference in the mean monthly weight gain rate and specific growth rate at different rearing densities （P〉 0.05）. （2） At the end of the experiment, the survival rate of D1 （50%） was significantly higher than D2 （35%） and D3（20%）; （3） Feed conversion ratio increased with the increase of density, which trend was D3〉D2〉D1; （4）Although the yields of different density groups were similar, the cost of high density group of purchasing and feeding seedstoek was greater than the low density group, however the group of low density could gained higher net profit and return-on-investment. Hence, 12 000 ind/hm2 was considered to be a suitable stocking density for P. trituberculatus female juveniles, and too high stocking density would increase costs and reduce profitability.