Effect of Culture at Low Salinity on Muscular Nutrient Composition of Mud Crab Scalla paramamosain
In order to investigate the effect of low salinity on the nutrient composition of muscle of mud crab Scalla paramamosain,the mud crab with body mass of(254±36.81)g were reared in circulating water for 60 days,one crab per box,exposed to salinity of 5(S5),10(S10),15(S15),20(S20),and 25(S25,control group)in the aquatic environment,at a salinity reducing rate of 1/d from natural sea water with salinity of 25 to 20,and then reducing the salinity to 1 and 10 at an average daily amplitude of 2.5,and finally reducing the salinity to 5 at an average daily rate of 2,each group with 3 replicates and 30 crabs in each group.Results showed that there was muscular crude protein content from(16.2±1.9)%to(19.5±0.7)%in the mud crab cultured in low salinity,without significant difference from that in the crab in the control group.There was significantly higher muscular crude fat content in groups S10 and S25 than that in the control group(P<0.05).The mud crab in group S15 had total muscular amino acids(TAA)amount of(18.63±0.91)%,essential amino acid(EAA)of(6.49±0.41)%and flavored amino acid(DAA)(7.48±0.21)%,higher than those in the control group,with the optimal amino acid index(EAAI)of 80.36.The contents of highly unsaturated fatty acids(HUF A)and EPA were found to be significantly higher in group S10than those in control group(P<0.05),with the maximal n-3 polyunsaturated fatty acids(Σn-3PUFA)content(33.0%).The findings indicated that the muscle nutrition is improved in the mud crab cultured at salinity from 10 to 15.