In May, Japanese fisherman Tadasuke Nakamura noticed he had an abnormally large haul of bluefin tuna in his set net off the Pacific coast of Hakodate, on Japan's northern island of Hokkaido.
Hundreds of the prized sushi fish crowded the net, but he had to let many of them go.
Japan has an annual catch quota and if Nakamura had kept the haul he would have had no quota left for the colder months when bluefin tuna are fattier, tastier, and fetch a higher price.
"It's truly upsetting to have to release fish that are right there in the net," said Nakamura, whose method of fishing involves anchoring large fixed nets close to the shore.
Fishermen in Japan have reported an abnormal surge in the number of the once-endangered bluefin tuna in surrounding waters this year. In Nakamura's hometown of Hakodate, the fishing industry is already grappling with a severe decline in the population of the once ubiquitous squid.
Like Nakamura, many fishermen have been unable to capitalise on the abundance of the species early in the season.
An international quota system in place since 2015 means Japan is allowed to catch no more than 8,421 tonnes of bluefin tuna weighing 30 kg (66 pounds) or more this year in the waters of the western and central Pacific, extending south of New Zealand and covering about a fifth of the world's surface.
While Japan's quota was increased by 50 per cent from 2024 for this year and last year, the sheer scale of the surge in the bluefin tuna population means many Japanese fishermen are close to reaching their 2026 quota. Set-net fishermen are also finding that when they release the bluefin they also lose much of their intended catch, eating into their sales.
In April, large-sized bluefin tuna hauls around Japan's coast nearly doubled from last year, data from the fisheries agency showed.
To deal with the issue, Japan is proposing a revision to the quotas, endorsing an automatic formula seen as middle-of-the-road — neither aggressive nor conservative — which would increase the western and central Pacific region's fishing quota for large bluefin tuna by 25 per cent next year.
At the same time, the proposal would reduce the allowance for bluefin tuna weighing less than 30 kg by six per cent, Japan's Fisheries Agency said, to protect the breeding population.
The working group of the organisation responsible for managing the region's migratory fish stocks, the Western and Central Pacific Fisheries Commission (WCPFC), starts meeting in Nagasaki, southern Japan, on Wednesday. The quota for the next two years will be finalised at the group's regular session in Vanuatu in December.
"One reason for the increase in bluefin tuna is that resource management has been successful," said Masahiko Ariji, professor at Kindai University's World Economy Research Institute, referring to years of conservation efforts.
Changing ocean temperatures are also altering the routes of migratory species, including for bluefin tuna, the international non-profit Marine Stewardship Council said in a report published in November.
The WCPFC says the quota system successfully ended overfishing and replenished the stock of spawning biomass, which reflects the breeding population, to 144,000 tonnes in 2022 from 12,000 tonnes in 2010.
"If there were a larger quota, we could have a massive haul," said Toshiharu Uratani, a fisherman in the western prefecture of Fukui, adding he had fulfilled his half-year quota for large tuna in the first three months.
"As it stands, we have to let the fish go, which means our efforts are wasted. The tuna are getting in the way."
(Reporting by Kaori Kaneko, Editing by Chang-Ran Kim and Kate Mayberry)
