Review of Japanese fisheries and tropical tuna catch in the Indian Ocean

Japanese longline vessels have been targeting bigeye and yellowfin tunas along with albacore and southern bluefin tuna. The fishing effort for longline fishery fluctuated and sharply decreased in recent years, which is mainly by the decrease in the northwestern part due to piracy activities. Both bigeye and yellowfin tuna catch peaked during 1960s, sharply decreased in the 1970s, fluctuated after that, and sharply decreased around late 2000s. High CPUE for bigeye and yellowfin tuna was observed mainly in the eastern and western Indian Ocean, respectively. Japanese purse seine vessels have been targeting skipjack, yellowfin and bigeye tuna since 1970s. Fishing effort of purse seine peaked in 1992, and then decreased until 2000, after that it kept low level. The annual catch of tropical tuna coincided with the trend of effort. The vessels mainly operated in the eastern part after 2000s. Set for logs or natural objects was main component before mid-1980s, and then FAD associated schools become dominant. Size data for bigeye and yellowfin tuna were collected by several methods. Fish size does not largely differ by decade, area and quarter.