This experiment was conducted to investigate the effects of residual salts (mainly NaCl) and free amino acids in mysid Archaeomysis vulgaris meal on the growth of juvenile Japanese flounder Paralichthys olivaceus. Five experimental diets were designed. Diet 3 contained fish meal as sole protein source. Fish meal was replaced by de-salted mysid meal at the level of 37.5% and 77.5% in diets 1 and 2 respectively. Diet 4 contained 82.0% mysid meal and diet 5 was a commercial diet. Fish with mean body weight 0.16 g (experiment I) and 1.35 g (experiment II) were fed on the above diets for 14 days, respectively.
Both size of juvenile flounder (0.16 and 1.35 g) fed the 77.5% de-salted mysid meal diet showed significantly better (p<0.05) growth than that fed the 82.0% mysid meal diet. These results clearly indicated that the excess amount of salts in the diet reduced the growth of juvenile flounder. On the other hand, the best growth was shown in the fish fed the 37.5% de-salted mysid meal diet containing 81.4 mg/g free amino acids (FAA) in total nitrogen compounds. The FAA analyses of fish total nitrogen compounds showed a similar profile to 37.5% de-salted mysid meal diet. These results suggested that growth of Japanese flounder juvenile was found to be affected by dietary FAA levels in de-salted mysid meal.