Fatty acid and sterol changes in razor clam Sinonovacula constricta (Lamarck 1818) reared at different salinities

Fatty acid and sterol changes in razor clam Sinonovacula constricta (Lamarck 1818) reared at different salinities were investigated. In one experiment, juvenile S. constricta with shell length of 1.63 ± 0.11 mm were firstly cultured at 13 psu for 10 days, and then cultured at 8, 13, 18, and 23 psu for another 5 days. In another experiment, adult S. constricta with shell length of 15.54 ± 0.80 mm were cultured at 13 and 23 psu for 40 days. On the 25th day, half of the S. constricta cultured at 13 psu were transferred to 23 psu for another 15 days. The results showed that higher salinity significantly decreased growth rate and crude lipid content in S. constricta. The proportions of long chain-polyunsaturated fatty acids (LC-PUFAs, C ≥ 20, double bonds ≥ 3) were significantly increased in S. constricta cultured at higher salinity as compared with those at lower salinity. The proportion of cholesterol was firstly increased and then significantly decreased with increasing salinity. The proportion of brassicasterol was higher in S. constricta cultured at higher salinity, while proportions of other plant sterols showed no obvious change trends. Interestingly, when S. constricta were around 60 days old with shell length of 32.06 ± 1.13 mm, the inhibitory effect of high culture salinity on growth rate was weakened, but the nutritional value was significantly improved. The results of this study suggest an optimal culture mode for S. constricta, i.e. if S. constricta were firstly cultured at lower salinity (10-15 psu) and then exposed to higher salinity (20-25 psu) for a short period of time before harvest, a combination of both optimal production and nutritional value would be achieved.