Are Bluefin Tuna Endangered? Atlantic Bluefin's Recovery

The status of the three bluefin tunas

There are three species of bluefin tuna, and all were badly overfished in the late 20th century. The IUCN reassessed them, along with other commercial tunas, in September 2021:

The IUCN Red List judges the risk of extinction for a species as a whole. A species can be listed as Least Concern while some of its regional populations are still far smaller than they once were, and that is the case for the Atlantic bluefin tuna.

How overfishing pushed bluefin toward collapse

For most of history, bluefin were caught on a small scale. That changed after the Second World War. In the 1960s, purse-seine boats off the US East Coast caught huge numbers of young bluefin for canning, and an intensive fishery in the North Sea and off Norway helped wipe out the large summer runs of bluefin in northern Europe.

From the 1970s, demand for raw bluefin in Japan made the fish one of the most valuable in the world, and the fatty belly meat became a luxury. Fleets targeted the big fish that gather to feed off New England and Atlantic Canada and to spawn in the Mediterranean, where dense spawning schools made them especially vulnerable. In the 1990s and 2000s, the growth of tuna ranching, in which wild fish are caught and fattened in sea pens, removed many young fish before they could breed.

Catch limits existed but were set too high and widely ignored. In the mid-2000s, scientists estimated that real catches in the eastern Atlantic and Mediterranean were about 50,000–60,000 tonnes a year, far above the official limit. In 2009, ICCAT, the international body that manages Atlantic tunas, reported that over the previous 40 years the eastern stock had declined by about 72% and the western stock by about 82%.

The turning point

By the late 2000s, many scientists and conservation groups feared that the eastern stock would collapse. In 2009, Monaco proposed banning international trade in Atlantic bluefin by listing it on CITES Appendix I. The proposal was voted down in March 2010, by 68 votes to 20 with 30 abstentions, but the debate put strong pressure on ICCAT.

ICCAT had already put a recovery plan for the eastern stock into force in 2007, and it now tightened it sharply. The eastern catch limit was cut to 13,500 tonnes for 2010, a fraction of the earlier legal and illegal catch. Rules on minimum size and fishing seasons were enforced, independent observers were placed on fishing and farming operations, and a catch-documentation system was introduced to track bluefin from the sea to the market.

These measures worked better than many expected. Bluefin produce millions of eggs and grow quickly when young, and a run of strong year classes, helped by good ocean conditions, rebuilt the eastern stock. As it recovered, catch limits were raised again, and in 2022 ICCAT adopted a management procedure, a pre-agreed rule that sets future limits from survey data.

The 2021 reassessment

When the IUCN announced its tuna reassessment in September 2021, four of seven commercially fished tuna species had improved. The Atlantic bluefin moved from Endangered to Least Concern, the southern bluefin from Critically Endangered to Endangered, and the albacore and yellowfin from Near Threatened to Least Concern.

The IUCN described this as evidence that well-enforced catch limits can work. It also stressed that many regional tuna stocks remain depleted, naming the bluefin of the western Atlantic as one of them.

Why scientists still worry

The western Atlantic stock, which spawns mainly in the Gulf of Mexico, is much smaller than the eastern one and has recovered far less. NOAA Fisheries reported in 2021 that it was not being overfished, but whether it is still depleted is uncertain. Western fish appear to mature later, at around 8 years, so the stock rebuilds slowly. The 2010 Deepwater Horizon oil spill struck the Gulf of Mexico during the spawning season, and its long-term effects on young bluefin are hard to measure.

Other concerns include illegal fishing, the heavy demand for wild fish to stock ranches, and climate change, which is shifting where bluefin and their prey are found. The southern bluefin, managed separately, remains far below its historical size, while a 2024 assessment found that the Pacific bluefin had rebuilt from about 2% of its estimated unfished size around 2010 to about 23% by 2020.

Bluefin back in northern Europe

One of the most visible signs of recovery has been the return of bluefin to northern Europe. After vanishing from the North Sea and Norwegian waters in the 1960s, giant bluefin began to reappear in the mid-2010s off Norway, Denmark and Sweden, and in growing numbers off Ireland, Cornwall, Wales and Scotland. Researchers in these countries have tagged returning fish to follow their migrations.

Warmer seas and recovering prey may also play a part, so the return reflects both better management and a changing ocean. For the size of these returning giants, see How big do bluefin tuna get? Sharks have not been so lucky: many species are still declining under fishing pressure, as described in How many sharks are killed each year?