Nutritional studies related to the development of mass production techniques of quality larvae

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One of the most important and fundamental approaches to the successful mass propagation of quality larvae is to cultivate quality broodstock which can produce fertile eggs and to culture hatched larvae with quality formulated microdiets or live foods. From this viewpoint several nutritional studies have been carried out in this two-year project. The results obtained are summarized as follows.With regard to broodstock diet, a newly-developed soft-dry pellet (SDP) was found to be suitable for yellowtail and supplementation of 30ppm astaxanthin to SDP enhanced spawning and quality of eggs. As for the data on nutritional requirements essential for development of microdiets, experiments were conducted on vitamin C (VC) and thiamine. In larval flounder VC requirement was affected by dietary n-3 HUFA levels, and was 10mg/100g diet when n-3HUFA was 2% in diet. In red seabream larvae TBA value of muscle suggested that VC can reduce lipid peroxidation in muscle. The thiamine requirement of larval Kuruma shrimp was found to be around 14mg/100g diet based on the maximum growth and the hepatopancreatic thiamine pyrophosphate content. On the other hand, in experiments with live foods. DHA requirement was determined for some marine larval fish at the stage subsisting on Artemia. On a dry matter basis of Artemia, the DHA requirement was 0.95-1.62% for red seabream, 1.39-2.63% for yellowtail and 1.6-2.2% for striped jack. These results are valuable information for establishment of techniques related to mass seed production of various species.