With tighter enforcement of limits on juvenile bluefin tuna in Japan, and no method of quota pooling or transfer among Japan’s 47 prefectures, there is a risk that they will become a “choke species” putting a brake on fishing for other species like yellowtail.
A choke species is a species with a small quota that is often caught as bycatch with other preventing efficient utilization of quota for the target species. In mixed fisheries, the effects of choke species will depend on fishermen’s capacity to avoid catching the species with the most restrictive quotas and their ability to take advantage of any quota-swapping mechanisms.
In 2015, the Japanese government set catch quotas for Pacific bluefin tuna for troll fishing, set-net fishing and purse seine fishery in accordance with the Conservation and Management Measure adopted by the Western and Central Pacific Fisheries Commission (WCPFC). The commission agreed to more than halve catches of juvenile bluefin tuna weighing less than 30 kilograms from the annual average levels from 2002 through 2004 and keep adult fish catches below those levels.
Based on this rule, Japan required coastal bluefin fishermen to obtain a license and set total allowable catches (TAC) by region and fishing method. However, suspected violations surfaced in Nagasaki and Mie prefectures. As the initial request for voluntary compliance was not met with success, the government switched the regional allotments to prefectural quotas and threatened to impose penalties on operators who exceeded the limits.
In 2017, Japan exceeded its TAC for a second year. Many juvenile bluefin were caught in set nets for salmon in Hokkaido. The bycatch in Hokkaido set nets reached 600 metric tons (MT), exceeding the bycatch limit of 580 MT for the whole nation for set nets through June of 2018.
To overcome the problem, set nets for salmon and yellowtail will need to be redesigned to allow escapement of non-target species, though this will also allow some escapement of the target species. There also needs to be a system to pool and reallocate unused quota among the prefectures to ease the risk of incidental catches shutting down a fishery.
The average wholesale price of fresh bluefin tuna at Tokyo’s Toyosu Wholesale Market in mid-February was JPY 4,881 (USD 43.86, EUR 38.57) per kilogram. Frozen was JPY 3,586 (USD 32.21, EUR 28.33).
Yellowfin tuna averaged JPY 1,692 (USD 15.20, EUR 13.36) for fresh and JPY 842 (USD 7.56, EUR 6.65) for frozen. Bigeye tuna averaged JPY 2,299 (USD 20.64, EUR 18.16) for fresh and JPY 1,086 (USD 9.75, EUR 8.58) for frozen. Southern bluefin was available only frozen, at JPY 1,823 (USD 16.37, EUR 14.40).
