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The weight gain of fish fed on the diets containing 12 and 25% of feather meal did not differ from that of fish fed on the control diet containing 80% of white fish meal, however, fish fed on the 37 and 50% feather meal diets gained less weight. The feed conversion efficiency and protein efficiency ratio of fish fed on the 12% feather meal diet were almost the same as in the control group, however, these efficiencies decreased as the proportion of feather meal in the diet increased from 25, 37 to 50%. Supplements of crystalline amino acids to the feather meal diet improved its nutritive value slightly. There was little difference in the proximate composition of the whole body together with the hematological and hematochemicalparameters among the dietary groups tested.The present study showed that 12 to 25% of feather meal is an appropriate substitute for fish meal in the diet of juvenile Japanese flounder.

Abstract.— Feeding experiments were conducted to evaluate corn gluten meal (CGM) as an alternative protein source for fish meal in the diet of Japanese flounder Paralichthys olivaceus. A diet containing 75% white fish meal as a sole protein source was the control, and 20, 40, and 60% of fish meal protein was replaced with CGM protein in the experimental feeds. Juvenile fish of about 8 g initial body weight were fed each diet to apparent satiation twice a day. 6 d per week for 8 wk at 20 C. Survival rates of fish ranged from 98 to 100% and were not significantly different (P > 0.05) among treatments. Final body weight, weight gain, feed efficiency and protein efficiency ratio of fish fed the diets containing CGM up to 40% substitution levels were not statistically different from those of fish fed the control diet. All production parameters for fish fed the diet replacing 60% of fish meal protein were significantly lower than the control (P≤ 0.05). Supplements of crystalline amino acids to the CGM diet improved the nutritive value of the diet. Since substitution up to 40% did not adversely affect hematological and hematochemical parameters as well as whole body composition of the cultured fish, it is suggested that up to 40% of fish meal protein can be replaced with CGM in the diet of juvenile Japanese flounder.

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The nitrogen budget of polychaete Perinereis nuntia vallata fed on Japanese flounder feces was estimated at 20°C. Worms of 0.2–0.6 g body weight ingested 4.9–25.7 mg/individual per day of flounder feces and excreted 1.2–5.5 mg/individual per day (dry weight) of fecal pellets corresponding to 12.2–44.1% (mean 22.4%) of fed flounder feces. Mean ammonia excretion rate of the worms fed the feces was 0.1 mg/individual per day. Based on the ingestion and excretion data and nitrogen content of flounder feces, worm fecal pellets and worm bodies, it was estimated that the worms assimilate 62.8% of nitrogen intake. In 3 weeks rearing with the flounder feces, commercial diets for flounder and polychaetes, and nitrogen assimilation rates for the worms were 46.3%, 47.4% and 53.7%, respectively. From these results, about half of the nitrogen ingested by the worms is converted into worm body tissue.