USEFULNESS OF COMMERCIAL AND NON-HEATED FISH MEAL DIETS FOR PACIFIC BLUEFIN TUNA Thunnus orientalis

摘要

Feeding prey fish larvae such as yolk-sac larvae of Japanese parrot fish Oplegnathus fasciatus and spangled emperor Lethrinus nebulosus was essential to avoid cannibalism and stable production of Pacific bluefin tuna Thunnus orkntalis. However, mass production of prey fish larvae is difficult because fully controlled spawning induction of bloodstock has not been established. Thus, we have tried to develop artificial diet for replacement of prey fish larvae for juvenile Pacific bluefin tuna production. In previous studies, it was suggested that feeding a casein peptide-based microdiet supplemented with inosine monophosphate sodium salt (IMP) as a feed attractant significantly improved feeding and survival of Pacific bluefin tuna. However, lower growth was still problem of the diet. It was suggested lower digestibility of conventional fish meal in Pacific bluefin tuna probably due to limited digestive ability of denatured protein in conventional fish meal by steamed process. In addition, there is nostudy examining effect of feeding a commercial diet on larval Pacific bluefin tuna. Therefore, this study investigated effect of non-heated fish meal based- and commercial diets on growth, survival of Pacific bluefin tuna.