The Japanese season for bonito tuna, popularly known as katsuo tataki (seared tuna loin) and katsuobushi (shaved bonito), has opened. But catches have been poor and retail prices are as high as double the usual.
The volume sold at Tokyo’s Tsukiji wholesale market in the first few days of May was only a little over 20 percent that of the same time last year. Individual fish were also smaller, ranging from 1.5 to 2 kilograms.
The wholesale price was four to seven percent higher, at an average of JPY 750 yen (USD 7.00, EUR 6.09) per kg, but the scarce large fish sold at a premium. In Tokyo supermarkets, bonito sashimi sold from JPY 200 to 300 yen (USD 1.87 to 2.80, EUR 1.63 to 2.44) per 100 grams, about twice that of last year.
Bonito (also called skipjack tuna) migrate north to Japan from the Philippines and Taiwan in spring. At this time, they carry less fat than when they return in the opposite direction in fall. The biggest landings are in Kochi, Wakayama and Chiba prefectures, along the path of the warm Kuroshio Current. The bright red color of the meat is its main attraction. It is often eaten as sashimi seared on the surface with a blow torch.
Though the migration traditionally begins in May, when the bonito season opens, it appears that the fish will not show up in large numbers for another month. Sea surface temperatures off Japan have been increasing since around 2011, resulting in altered fish migration patterns for everything from saury to tuna.
Tuna fishermen have been griping that their small early catches will not pay fuel costs, and some hold alternate theories for the change in migration patterns, such as a change in ocean ecology following the Great East Japan Earthquake or overfishing by other Asian countries.
Taiwan would be the main culprit under the latter theory, but generally, skipjack is one of the least threatened tuna species in the Pacific, and concerns about the Pacific skipjack fishery mainly relate to excessive bycatch of juvenile yellowtail and bigeye, with which they associate. Skipjack are fast-growing and short-lived, and there is considered to be an adequate stock of skipjack to sustain the current annual catch of about 1.7 million metric tons. So, for this species, the issue is more likely climate change than overfishing.
Half of the world’s skipjack tuna comes from the exclusive economic zones of Pacific island nations grouped into the bargaining block called the Parties to the Nauru Agreement (PNA). The group has instituted a Vessel Day Scheme regulating vessel days rather than total allowable catch and has raised fees, so that income to the member states has increased in the last six years from USD 60 million (EUR 52.6 million) to 400 million (EUR 350.5 million) last year. The group has also pushed conservation measures such as reducing fish aggregation devices (FADs), protecting whale sharks and putting observers on all vessels. In 2011, PNA skipjack tuna caught without FADs was certified by the Marine Stewardship Council as sustainable.
Japan’s annual imports of skipjack tuna (in all forms) amounts to a little over 300,000 metric tons and makes up a little less than half by volume of all tuna species imported. Japanese distant water fleet supplies nearly 70 percent of the total, with Taiwanese and Indonesia the leading foreign suppliers.
