Effect of Long-Term Low-Salinity Culture on the Survival, Growth, and Nutrient Composition of Mud Crab Scylla paramamosain

This study investigated the effects of long-term low-salinity on the growth performance, proximate composition, amino acid and fatty acid profiles of Scylla paramamosain. The salinity of the low-salinity-culture group(LC) and maintained-salinity-culture group(MC) were set at 5 and 25 respectively. After rearing for 30 d, the survival rate(SR) of the LC group was significantly lower, whereas the average daily molting frequency(ADMF) was significantly higher than those in MC group(P < 0.05). There were no significant difference for weight gain rate(WGR) and specific growth rate(SGR) between the two groups. The moisture content of the LC group was slightly higher than the MC group without significant difference. The contents of ash, crude lipid and crude protein in the LC group were lower than those in the MC group, but no significant differences were found except for ash content. A total of 17 free amino acids and 23 fatty acids were identified from the muscle of S. paramamosain. The total amino acids(TAA), essential amino acids(EAA) and essential amino acid index(EAAI) had no significant difference between the two groups. The crabs from LC group had a significantly higher HUFA, including EPA, DHA, ARA. The percentage of n-3 PUFA and the ratio of n-3/n-6 PUFA were significantly higher in the LC group. These results indicated that S. paramamosain rearing at low salinity had significantly decreased SR; however, the low-salinity environment significantly promoted the accumulation of unsaturated fatty acids(UFAs), especially the n-3 PUFA, which might be related to the osmoregulation mechanism.