Conflict over the allocation of Pacific bluefin tuna quota in Japan: How to allocate the quota of fluctuating fishery resources

The abundance of Pacific bluefin tuna Thunnus orientalis has decreased markedly in recent years and is subject to strict international fishing quotas. The quotas for purse seine, coastal, and other fisheries are allocated domestically. The rules for domestic allocation are unclear and in some areas the set net fishery greatly exceeded the limit in the 2017/2018 season. The allocation was decided before the allocation method was agreed upon among stakeholders. In this paper, we discuss the grounds for strict quota limitation and how to determine domestic quotas, their problems, and future prospects. By international agreement, there has been a drastic decrease in comparison with the past stock abundance. Japan agreed to the strict catch limit because they expected more recruits to be born in 2015 and 2016. We propose a population reproductive potential that is defined as the sum of the reproductive values of all individuals as a more reasonable indicator of stock abundance than the spawning stock biomass that is used for international fisheries management. It is rational to prioritise coastal fisheries when the stock is low and to allocate more to offshore fisheries when the stock is high to increase the overall catch. In theory, allowing transfer of the catch quota will decrease the release of high-price tuna, while keeping the total quota.