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| Effect of Replacement Percentage of Commercial Feed by Snails on Yield and Water Quality in Chinese Mitten Handed Crab Culture |
| WANG Haihou,SHEN Mingxing,LU Changying,SHI Linlin,ZHOU Xinwei,JIN Meijuan |
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Abstract Snail (Bellamya quadrata) was fed Chinese mitten handed crab (Eriocheir sinensis) as the re‐placement of commercial feed to mitigate nitrogen and phosphorus load in water in culture ponds .Chinese mitten handed crab was reared in a small pond ,and fed snails (a total of 6000 kg/hm2 ) and commercial feed (a total of 4500 kg/hm2 ) as a control group ,and fed the diets containing 0% ,25% ,50% ,75% ,and 100% of snails in the treatment groups to evaluate the effects of snail substitution ratios on yield ,water quality and economic benefits in Chinese mitten handed crab culture .Results showed that there was a quadratic curve relationship between the crab yield and snail substitution percentage ,indicating that crab yields and gross profits were all shown to be significant correlation with snail substitution ratios .Increase in the ratios of snail led to decrease in nitrogen contents in the water in the treatment groups while the phosphorus contents in the water in the treatment groups were less affected by the substitution ratios of snails .The median value of total nitrogen content in waters in the treatment groups were all lower than the standard of V water quality ,and the median value of total phosphorus content were all lower than the standard of Ⅲ water quality in the treatment groups .Comprehensive analysis of effects of replacement of commercial feed by snails on yields ,nutrients contents ,and economic benefits revealed that the optimal snail substitution ratios were recommended to be 37 .85% -51 .25% ,if substitution ratio was calculated by 40% ,the optimal snail feeding rate w as 14 550 kg/hm2 ,and the commercial feed 2700 kg/hm2 .
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Received: 25 November 2015
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