Status of Bluefin Tuna Farming, Broodstock Management, Breeding and Fingerling Production in Japan

Abstract

Development of bluefin tuna farming in Japan has a 30-year history. This paper reviews recent developments as well as the current status and problems of farming, broodstock management, and fingerling production in Japan. Farmed bluefin tuna by wild seed-stock comprises approximately 15–20% (2,400 tons) of the annual catch of bluefin in Japan. Comparisons among farms in Japan indicate that bluefin tuna growth is positively correlated with annual water temperature. Broodstock commence spawning at approximately 3–5 years of age, and eggs are collected from within the cages. The number of bluefin tuna eggs collected in Japan has varied greatly—between zero and about 500 million—with variance between farms and years. Current larval rearing techniques produce tens of thousands of fingerlings of 35–50 mm per season in Japan, but survival rates are 0.01–4.5%. Although there are the bottlenecks in egg collection and larval rearing under the present technology, the approaches for enhancing bluefin resources and the replacement of wild seed-stock by artificial fingerling to tuna farms have firmly been improving in Japan.