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Fishery Sustainability through Stock Management

Case Study of Pacific Bluefin Tuna in Iki, Nagasaki

November 2014

Research Fellow, Hiroshi Hamasaki

Senior Research Associate, Nozomi Kato

Senior Research Fellow, Takafumi Ikuta


With increasing concerns over the tightening international supply-demand of seafood, it is more important than ever for Japan to secure a stable supply by managing fishery stock in its surrounding waters. In particular, Pacific Bluefin Tuna (hereafter, “PBT”), of which Japan consumes 80% of annual global catches, has seen a consistent decline in population, with the number of mature fish in 2012 having fallen by approximately 30% from a recent peak in 1995. Approximately 99% of all PBT caught are immature fish, which has led Japan’s Fisheries Agency to formulate a stock management policy to be put into place in January 2015, whereby hauls of immature fish under 30kg will be reduced by 50%. There is much interest in the potential effectiveness of this policy.

In this study, we devise six different catch limit scenarios, and using population models we simulate the effects of each scenario on PBT stock (by weight). In the Business As Usual (BAU) scenario, the tuna population will drop by 98% between 2015 and 2040. In contrast, Scenario 1 (50% catch reduction of PBT under 3 years old) results in 60% population growth, and Scenario 4 (50% catch reduction of all ages of PBT) sees a 270% increase during the same time period. Other scenarios all see drops in overall PBT stock.

Simulations of the effects on PBT catch values were also performed using the case study of Iki-Island, Nagasaki, a leading producer of inshore fresh PBT. By evaluating the propagation effect from fisheries through other industries using inter-industry analysis, it appears that proper stock management would lead to increased revenue for fishermen, thereby increasing gross added value (regional GDP) and creating new employment opportunities. In the case of Iki Island, Scenario 1 is highly recommended, as it would increase the city’s GDP by JPY150m and increase employment by 35 fishermen between 2015 and 2040. The best case in terms of mid- to long-term sustainability would be Scenario 4, which would require fishermen to ride out the first few stormy years of reduced catch values, but would thereafter result in a JPY270m increase in catch value and 64 new jobs by 2040.

In order to increase the effectiveness of PBT stock management in Japan, the Fisheries Agency must test and verify the suitability and efficacy of its policy design while ensuring that all affected Japanese fishermen are aware of the measure. It should also consider providing short-term subsidies where necessary. Furthermore, Japan must cooperate with other countries that fish PBT and help establish management programs there as well. Economic evaluation methods can be used to help verify the effectiveness and likelihood of success when considering sustainable methods for balancing the recovery of fishery stock and regional economics.

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  • The full text is unavailable in English for this report.
    The original Japanese text is here [1703 KB].