Use of Fermented Fisheries By‐products and Soybean Curd Residues Mixture as a Fish Meal Replacer in Diets of Juvenile Olive Flounder, Paralichthys olivaceus

A 10‐wk feeding trial was conducted to evaluate the potential use of fermented fisheries by‐products and soybean curd residues mixture (FFSM) as a partial replacement for fish meal (FM) in the diet of juvenile olive flounder, Paralichthys olivaceus. Five experimental diets were formulated with FFSM replacing 0, 15, 30, 45, and 60% of the FM protein (FFSM 0 , FFSM 15 , FFSM 30 , FFSM 45 , and FFSM 60 , respectively). Juvenile olive flounder averaging 5.99 ± 0.08 g (mean ± SD) were randomly distributed into aquaria at 15 fish/aquarium, with three replicate aquaria for each experimental diet. Weight gain (WG) of fish fed FFSM 0 , FFSM 15 , and FFSM 30 was significantly higher than that of fish fed FFSM 45 and FFSM 60 ( P  < 0.05). Also, WG of fish fed FFSM 45 was significantly higher than that of fish fed FFSM 60 ( P  < 0.05). There were no significant differences in WG among fish fed FFSM 0 , FFSM 15 , and FFSM 30 ( P  > 0.05). Specific growth rate (SGR) of fish fed FFSM 15 was significantly higher than that of fish fed FFSM 45 and FFSM 60 ( P  < 0.05). Also, SGR of fish fed FFSM 0 , FFSM 15 , FFSM 30 , and FFSM 45 was significantly higher than that of fish fed FFSM 60 ( P  < 0.05). There were no significant differences in SGR among fish fed FFSM 0 , FFSM 15 , and FFSM 30 and among those fed FFSM 0 , FFSM 30 , and FFSM 45 ( P  > 0.05). Feed efficiency (FE) and protein efficiency ratio (PER) of fish fed FFSM 60 were significantly lower than those of fish fed FFSM 0 , FFSM 15 , FFSM 30 , and FFSM 45 ( P  < 0.05); however, there were no significant differences in FE and PER among fish fed FFSM 0 , FFSM 15 , FFSM 30 , and FFSM 45 . Hepatosomatic index of fish fed FFSM 0 , FFSM 15 , and FFSM 30 was significantly higher than that of fish fed FFSM 60 ( P  < 0.05); however, there were no significant differences among fish fed FFSM 0 , FFSM 15 , FFSM 30 , and FFSM 45 and among those fed FFSM 45 and FFSM 60 . No significant differences were observed in condition factor and survival rate among all dietary groups tested. The whole‐body proximate composition averaged 75.0 (% dry matter basis [DM]), 8.66 (% DM), 16.38 (% DM), and 76.1%, for crude protein, crude lipid, ash, and moisture, respectively. Based on growth performance, the FFSM could replace up to 30% FM protein by the ANOVA test; however, broken‐line model analysis indicated 28.7% as an optimum replacement level in juvenile olive flounder diets.