'One fish worth $7,000' — Korea's bluefin bonanza is actually a headache for fishers

"We can't eat it, we can't sell it — we have to throw it back."

Pacific bluefin tuna has long been prized as one of the most expensive fish for raw consumption. Until recently, Korean diners had to make do with frozen imports thawed at the table. But times have changed.

Large bluefin tuna have begun appearing in Korea's East Sea. Last year, a 314-kilogram specimen was caught and sold for 10.5 million won ($7,120).

Of late, catches of several thousand bluefin at a time have been recorded, sending prices sharply lower.

The surge is a consequence of faster-than-expected rises in sea surface temperatures. Some researchers now say Korea's East Sea coast has effectively become a bluefin tuna habitat.

The problem is that the bluefin boom has a hard ceiling. With the year barely half over, the annual catch quota for bluefin tuna is nearly exhausted.

In practice, that means any bluefin caught now must be released. Fishers along the East Sea coast have found themselves dreading the moment a bluefin ends up in their nets.

Over June and July, catch quotas allocated to bluefin-fishing areas along the coasts of Gangwon Province and North Gyeongsang Province have been largely used up. Once a region's quota is exhausted, any bluefin tuna caught there cannot be brought ashore — they must be returned to the sea.

According to the Ministry of Oceans and Fisheries, Korea's baseline bluefin tuna quota this year stands at 1,219 metric tons — 718 tons for small fish under 30 kilograms and 501 tons for large fish weighing 30 kilograms or more. Fishers on the ground say that allocation is nowhere near enough.

Mass catches have been occurring repeatedly along the North Gyeongsang and Gangwon coasts. In June, more than 2,000 bluefin tuna weighing around 100 kilograms each were caught in waters off Uljin and Yeongdeok over just two days — more than 220 tons, equivalent to roughly 20 percent of the entire annual quota, in a matter of hours.

Bluefin tuna were not historically common in Korean waters. Smaller individuals occasionally turned up in East Sea nets, but large specimens — the kind prized for high-end sashimi — were rarely seen. Since the 2020s, however, bluefin catches have jumped sharply, and analysts say the East Sea is becoming a primary habitat for the species.

According to the National Institute of Fisheries Science, bluefin tuna eggs and juvenile fish were first confirmed around Ulleungdo and Dokdo in 2021. The number of eggs recorded has since jumped: 16 in 2021, 15 in 2022, 3 in 2023, 111 in 2024 and 250 in 2025. Last year, bluefin tuna larvae were also found in coastal waters off Goseong-gun.

In plain terms, newborn bluefin tuna are now being found in Korean waters. Newly hatched larvae cannot travel long distances on their own, which means spawning is occurring nearby or the fish were in those waters immediately after hatching.

Climate change is the primary driver behind bluefin tuna moving into Korean coastal waters from the open Pacific. As global warming pushes sea temperatures higher, the viable habitat range of bluefin tuna — a subtropical species — has expanded northward.

According to the National Institute of Fisheries Science, surface water temperatures in Korea's coastal seas rose 1.44 degrees Celsius over the 56 years from 1968 to 2023 — more than double the global average increase of 0.7 degrees. The East Sea, where bluefin are being caught, warmed by 1.9 degrees, a notably faster rate than the Yellow Sea (1.27 degrees) or the South Sea (1.15 degrees).

The implication is straightforward: as climate change continues, bluefin catches are likely to keep growing. The trouble is that internationally set catch limits are leaving fishers unable to sell the fish they haul in.

The problem goes beyond simply being unable to sell the fish. Bluefin tuna are not a species East Sea fishers actively target. Coastal set-net operations are designed to catch migratory fish such as yellowtail, squid and mackerel by fixing nets in the water. There is no way to selectively exclude bluefin from those nets.

Once a quota is filled, any live bluefin that enter the nets must be released, while dead individuals cannot be sold as normal product. Delaying operations or opening nets to release bluefin can also disrupt catches of the other species the fishers were actually after. The more bluefin appear, the greater the operational burden — a bumper catch that creates nothing but problems.

Over-quota bluefin have become a genuine nuisance. Because they cannot be sold, they generate only costs — for transport or disposal. Since most are already dead, releasing them back into the sea is not an option either. There have been cases of discarded over-quota bluefin washing up on beaches.

The South Korean government has been pursuing diplomatic efforts to expand its quota, and last year succeeded in securing an increase. But the higher allocation still falls short of what fishers are actually catching. Japan faces the same problem. It holds roughly 10 times Korea's bluefin quota, yet fishers across the country are also exceeding their limits, fueling growing frustration.

Against that backdrop, South Korea and Japan called for an adjustment to bluefin catch limits at a joint meeting of the Western and Central Pacific Fisheries Commission and the Inter-American Tropical Tuna Commission, held in Nagasaki, Japan, from July 8 to 14.

According to the meeting records, South Korea proposed a compromise: rather than immediately redistributing existing national quotas, any future increases to the large-fish allocation should be distributed equally among Japan, South Korea and Taiwan. Seoul also proposed adjusting the conversion factor applied when small-fish quotas are transferred to large-fish quotas in line with the latest science, and allowing quotas to be managed flexibly across multiple years rather than on an annual basis. The proposals failed to achieve consensus, and the meeting produced no concrete outcome.

An abundance of bluefin tuna is not simply good news. The arrival of a new species in coastal waters is evidence that existing species are also on the move. If the fishing industry cannot adapt at the pace of climate change, the broader marine ecosystem could suffer.

The disappearance of cold-water species is the clearest sign of that shift. Pollock, once caught in abundance in Korean waters, has long since vanished from the sea. Annual squid catches, which exceeded 160,000 tons as recently as 2014, fell to 36,000 tons by 2022.

The government has responded with a comprehensive climate change adaptation plan for the fisheries and aquaculture sector, covering support for fishers switching to different vessel types and greater flexibility in production systems and regulatory frameworks. A Ministry of Oceans and Fisheries official said the goal is "to develop new policy tools to minimize damage to fishers from climate change and to improve the structural resilience of the fisheries and aquaculture industries."