Juvenile mangrove red snapper (Lutjanus argentimaculatus) is euryhaline but utilizes feed better in seawater than in brackish water

Abstract

The mangrove red snapper (Lutjanus argentimaculatus) inhabits seawater and brackish water environments, but the optimal salinity for rearing the species in aquaculture systems has never been assessed. Here, triplicate groups of juvenile L. argentimaculatus (9.16-9.17 g body weight) were reared in various salinities (0, 7.5, 15, 22.5, and 30‰) for eight weeks; and growth, feed utilization, digestive enzyme activities, muscle quality, and whole-body composition were investigated at the end of trial. Food rejection and mortality gradually increased over the first three weeks among fish reared in 0 and 7.5‰ treatments; while the growth performances of the other three remaining treatments were similar, with a specific growth rates of 1.78-2.08% body weight/day, p > 0.05. However, feed conversion ratio of the fish reared in 30‰ treatment, which was 4.12 g feed/g gain, was significantly (p < 0.05) lower than those of the fish reared in 15 and 22.5‰ treatments, which were 5.31 and 5.16 g feed/g gain, respectively. In addition, it was observed that digestive enzyme activities, muscle quality, and whole-body composition were not affected by the different levels of water salinity. These findings confirm the euryhaline characteristics of juvenile mangrove red snapper, and the observed feed conversion ratios support rearing this species in a salinity of 30‰.