The Influence Of Ph, Salinity And Food Phosphorus On The Growth Of Nipponense

Two experiments were conducted to evaluate the dietary phosphorus requirement of M nipponense reared in calcium-free water. A basal dietary was supplemented with different phosphate type (P1 or P2) or graded levels of phosphorus (0.723%P2,0.909%P2,l . 108%P2,l .292% P2,1 .342%P2) and fed for 4 weeks. The results suggest that P supplementation can improve growth rate and P2 is more efficient than P1 as phosphorus source for M.nipponense. Length gain and moulting frequency data indicated that 1.108% dietary P2 was optimum for good growth. At l.108%P2, the bone, hepatopancreas and muscle phosphorus concentration was observed at the maximum and AKP and protease at the most active level. The growth of M.nipponense was measured at salinity of 7%o,14%oand 20 % and pH value of 7.6,8.8,9.8. The results clearly showed that M.nipponense had the highest growth at 14% salinity and pH7.6. The survival rate was not affected by external salinity. In comparison to a pH of 7.6, long term exposure to high pH significantly decreased weight gain and increased moulting frequency. The activity of AKP and protease was influenced by environmental salinity and alkalinity. At 14% salinity and pH7.6, the enzyme activity was the highest.