Growth, Survival and Cost-Efficiency of Mangrove Red Snapper Lutjanus argentimaculatus (Forsskål, 1775) Reared in Freshwater Lake Net Cages

The mangrove red snapper Lutjanus argentimaculatus (Forsskål, 1775) is a high value, euryhaline marine fish with potential as a species for freshwater aquaculture. This study evaluated the growth and cost efficiency of the species in floating net cage in a freshwater lake comparing two feed treatments (each with three replicates): (1) trash fish; and (2) commercial dry pellets, fed to apparent satiation. Fish were reared for seven months in 5 x 5 x 3 m3 net cages at a stocking rate of 5 fish.m-2. Snappers fed trash fish achieved significantly higher (P < 0.05) weight gain (mean ± SE = 345.7 ± 2.2 g), absolute growth rate (1.65 ± 0.01 g.day-1) and specific growth rate (1.44 ± 0.04 %.day-1) than snappers fed the commercial feed (282.4 ± 11.85 g, 1.34 ± 0.06 g.day-1 and 1.28 ± 0.02 %.day-1, respectively). Survival rate was (>90 %) in both treatments and did not differ significantly different between treatments (P > 0.05): it was 93.24 ± 0.59 % for trash fish and 93.82 ± 0.30 % for the commercial feed. The food conversion ratio (FCR) was much greater for the trash fish treatment (4.96 ± 0.01) than the commercial feed (1.59 ± 0.05). Both treatments were economically feasible with benefit-cost ratios of 0.81 and 0.63, respectively, but with relatively higher total sales and net income, benefit cost ratio and return on investment (ROI) and lower payback period for trash fish fed snapper. This study demonstrates the feasibility of rearing mangrove red snapper in cages in a freshwater lake at 3 fish m-2 density using trash fish as feeds.