๐ฌ This Summer, Bluefin Tuna Are Pouring Into Korea's East Sea — and the Catch Is a Headache, Not a Windfall — Woody Magazine, Jun. 23, 2026
Woody Magazine
๐ฌ Science
This Summer, Bluefin Tuna Are Pouring Into Korea's East Sea — and the Catch Is a Headache, Not a Windfall
Climate is redrawing the map of the sea. The quota holding those fish back is the very tool that pulled the species off the edge of extinction a decade ago.
Jun. 23, 2026 (Tue.)
This summer, something strange happened off Jumunjin, a fishing port on South Korea's east coast. A set-net — a large trap anchored in one place to catch whatever swims into it — hauled up more than 170 bluefin tuna in a single day. The largest stretched two meters and weighed 140 kilograms. Bluefin is the most prized tuna in the world, and here it was, arriving by the dozens in nets that had been set for squid.
By any ordinary logic, the fishermen should have been thrilled. Instead, one of them put it bleakly: the tuna, he said, are wiping out the squid.
The East Sea was never tuna country
Bluefin tuna like warm water. In Korean seas they used to turn up only now and then, down south near Jeju Island or along the southern coast — never up in the cold East Sea (the body of water between Korea and Japan). But as the East Sea has steadily warmed, the small fish that bluefin feed on, mackerel and sardine, have drifted north, and the tuna have followed them and stayed. The National Institute of Fisheries Science, a government research body, now treats this not as a passing visit but as a structural shift: the East Sea may be becoming a new spawning ground for bluefin.
It's worth pausing on the squid. Bluefin do eat squid — the U.S. National Oceanic and Atmospheric Administration (NOAA) lists it among their prey, alongside sardine, anchovy and mackerel — so it is tempting to pin the squid's disappearance on the tuna. But the real cause lies elsewhere. Common squid prefer cold water, and as the sea warmed they retreated to colder waters; heavy fishing, much of it by Chinese vessels, did the rest. The East Sea squid catch has collapsed by more than 90 percent, from 8,652 tons in 2020 to just 852 in 2024. Whether or not tuna eat squid, the force that pushed the squid out and the force that drew the tuna in are one and the same: warmer water. What we are watching is not one fish eating another. It is a single rising temperature swapping out the entire cast of the sea.
So why is a bumper catch a problem?
That much — climate redrawing the map of fish — is a familiar story by now. The twist comes next. Bluefin tuna cannot be caught freely. How much of it each country may land in a year is fixed by an international body, the Western and Central Pacific Fisheries Commission (WCPFC), which negotiates a broad national limit every two years; the government then parcels that limit out by region and year, adjusting it midstream as the catch unfolds. Korea's share this year is 1,219 tons. Exceed that quota, and any tuna that swims into the net has to be released — or the boats have to stop fishing altogether. And that 1,219-ton figure is itself an increase: as the stock recovered, Korea's limit was raised 63 percent from 748 tons at the end of 2024, with the allowance for large tuna (over 30 kilograms) jumping more than sixteenfold, from 30 tons to 501.
The trouble is that the quota fits badly with the way these fish are caught. A set-net takes whatever enters it; when tuna arrive in a mass, there is no picking and choosing. Gangwon Province's share this year was 92 tons — and by June 9, some 85 tons had already been landed, all but exhausting it. The province scrambled, and the ministry tacked on another 200 tons, lifting the limit to 292. Even then, no one feels safe, because tuna caught beyond the limit — the less marketable ones especially — end up dumped back into the sea. Last July, a set-net off Yeongdeok, on the east coast, suddenly held more than 1,300 large tuna; most were discarded because the quota was already spent, and the rotting fish turned into a problem of stench and pollution all its own. The more that come in, the more get thrown away. And when the catch does reach the auction floor, the glut weighs on the price — bluefin at Ganggu Port has changed hands for as little as 9,700 won, roughly seven U.S. dollars, a kilogram.
That quota is the thing that saved the tuna
So is the quota the villain? Should it simply be scrapped, or raised sky-high? Here is the second reversal. Barely a decade ago, Pacific bluefin tuna was a fish staring at extinction. Decades of overfishing through the 1990s and 2000s drove the spawning stock down to about 2 percent of its unfished level by 2009–2012, according to NOAA — perilously close to the point of no return. In 2011 the WCPFC's members agreed to cut their catch together, sparing young fish so they could grow and breed. The recovery was swift: by 2022 the spawning stock had climbed back to 23.2 percent of its unfished level, clearing an international target a full decade ahead of schedule. The quota now tying the hands of east-coast fishermen is the very mechanism that brought the species back from the brink.
The sea has changed; the map has not
The real problem, then, is not whether the quota is too large or too small. It is a lag. The international limit is set against past catch records and renegotiated only once every two years — and climate does not wait two years. It is redrawing the map of the sea right now, pushing the tuna northward as we speak. Nor is the government standing still: it raised the national limit by 63 percent, tripled the allocation for North Gyeongsang Province, and still had to add another 200 tons to Gangwon's. And yet the quotas keep running dry and the tuna keep being thrown back. It is not that the system is lazy. It is that the system, hurrying after the change, simply cannot move as fast as the sea.
This is not a problem unique to Korea, or to tuna. A 2022 study in the journal Global Change Biology found that most of the world's fishing quotas are anchored to historical records and barely account for the way warming is moving the fish. Under a high-emissions scenario, roughly a quarter of the stocks that cross national waters are expected to shift their range by 2030. The same thing has already played out elsewhere.
In the North Atlantic, it became the "Mackerel Wars." Around 2007, Atlantic mackerel began trailing the warming water north, appearing in Icelandic waters in numbers scarcely seen there before. Iceland's mackerel catch exploded from next to nothing in 2006 to more than 170,000 tons in 2011. Iceland and the Faroe Islands argued that since the fish had come to their waters, their share ought to grow as well, and unilaterally raised their own catch — colliding head-on with the European Union and Norway, who meant to protect the existing split. In 2013 the EU went as far as to threaten trade sanctions against the Faroes, barring their vessels from EU ports and blocking their imports. Echoing the "Cod Wars" that Britain and Iceland fought in the 1970s, the press dubbed it the Mackerel Wars. When fish swim across borders, a quota drawn along those borders turns into a diplomatic fight.
For the opposite case, there is no need to travel far — the same East Sea will do. Alaska pollock (myeongtae), once Korea's "national fish," was everywhere along the east coast through the 1980s. Then Gangwon's pollock catch collapsed from 6,722 tons in 1995 to a mere 3 tons in 2015 — four-hundredths of one percent of what it had been. A Seoul National University team reported in 2022 that as temperatures on the spawning grounds rose about 2 degrees Celsius in the late 1980s, the share of newly hatched larvae drifting down to the east coast fell by 74 percent. The pollock had moved off to colder waters in the north. Overfishing of juvenile pollock played its part too, though the researchers point to climate as the larger force. The government launched a "Save the Pollock" project, releasing hatchery-raised juveniles and, from 2019, banning the catch outright. The pollock never returned. In the same sea, the tuna arrived and the pollock left — and people could command neither.
And the East Sea is still changing. The bluefin now filling its waters is, in fact, a temperate tuna — a fish at home in both warm and cool seas. Behind it wait relatives that prefer it warmer still. Over two decades of monitoring set-nets off Goseong and Yangyang in Gangwon, the National Institute of Fisheries Science found that subtropical and tropical species already make up more than half of the catch around the 38th parallel; the surface temperature there has risen 1.1 degrees Celsius in twenty years. If the trend holds, warmer-water tropical tunas such as skipjack and yellowfin could become the East Sea's next guests — which is to say today's headache may not be the last.
And the new arrivals don't only come from the side; they come from up the food chain. Large sharks caught in East Sea nets jumped from a single case in 2022 to 44 by 2024, the National Institute of Fisheries Science reports — shortfin mako mostly, though a great white longer than two meters turned up in a net off Samcheok in the summer of 2023. The telling detail is the sharks' diet: when researchers examined what the netted sharks had been eating, the stomach contents included squid and octopus — and bluefin tuna. The sea the tuna moved into is now drawing the predators that hunt them. It is less alarming than it sounds, though: in the 66 years since 1959, not a single swimmer has been attacked by a shark at a Korean beach.
Longer-term efforts are now under way. The Ministry of Oceans and Fisheries will begin a sustained study of how climate is reshaping the country's fisheries in 2026, and plans to bring every coastal vessel under a total-allowable-catch (TAC) system by 2028. The next round of international quota talks opens as soon as July. It is a belated attempt to redraw the administrative map to match a sea that has turned the east coast from "a sea of squid" into "a sea of tuna." The bluefin washing up off the coast this summer are not simply the portrait of a bumper year. They are a mirror, held up to the gap between the ocean and the paperwork.
Sources
- Bluefin appearing along the east coast / climate shift in fish distribution — Gangwon Ilbo (link ↗)
- Fishermen blocked by the quota — Kyungbuk Maeil (link ↗)
- Catch surge and government response — Herald Economy (link ↗)
- Pacific bluefin stock recovery — NOAA Fisheries (link ↗)
- Bluefin diet (squid, sardine, anchovy) — NOAA Fisheries (link ↗)
- Korea's quota (718 t small / 501 t large) — WCPFC (link ↗)
- Quota raised to 1,219 t (+63%) — Ministry of Oceans and Fisheries (link ↗)
- Gangwon +200 t allocation (92→292 t) — JoongAng Ilbo (link ↗)
- N. Gyeongsang quota tripled; 2025 Yeongdeok discard of 1,300 tuna — NewDaily (link ↗)
- East Sea squid down 90% (warming, overfishing) — ScienceTimes (link ↗)
- Quota-vs-climate distribution lag — Global Change Biology, 2022 (link ↗)
- North Atlantic "Mackerel Wars" — The World (PRX) (link ↗)
- Pollock's disappearance from the East Sea — Kyunghyang Shinmun / Seoul National University (Frontiers in Marine Science, 2022) (link ↗)
- Subtropical/tropical species now over half of the catch near the 38th parallel (20-year monitoring); +1.1°C surface warming — National Institute of Fisheries Science (MBC report) (link ↗)
- Surge in large-shark bycatch in the East Sea (1 case in 2022 → 44 in 2024); diet analysis including bluefin — National Institute of Fisheries Science (Seoul Economic Daily) (link ↗)
- Great white netted off Samcheok; no beach shark attacks since 1959 — Yonhap fact-check (link ↗)
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