CLIMATE change is pushing Atlantic bluefin tuna northward, threatening historic breeding grounds and putting one of Spain’s most valuable seafood industries at risk.
Bluefin tuna, referred to in Spain as atun rojo (Thunnus thynnus), is the largest tuna species in the world, and one of the most valuable fish on the global market.
In 2019, a single bluefin tuna sold in Japan for over €2.7 million.
Now research is suggesting that climate change could dramatically reshape where the iconic species can survive and reproduce.
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An international study led by researchers at AZTI found that rising ocean temperatures are pushing Atlantic bluefin tuna more north.
The warming of both tropical and temperate waters, such as in the Mediterranean and Gulf of Mexico, could cause areas historically vital for tuna reproduction to become unsuitable.
The study points to warmer temperatures that will alter where fish can feed, reproduce or be caught.
In the bleakest scenario of greenhouse gas emissions, the study estimates that habitat sustainability in the Mediterranean could decline by 27%, with the Gulf of Mexico seeing a drop of up to 70%.
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This could seriously jeopardize the species’ reproduction success that has continued for over a millennium.
Due to the expected changes, fisheries are advised to integrate the effects of climate change by identifying new areas suitable for mating to ensure the harvesting of tuna remains sustainable.
‘Climate change not only affects ecosystems, but also how we manage marine resources,’ explained AZTI researcher Erauskin-Extramiana.
‘Anticipating these shifts is key to protecting both biodiversity and the livelihoods that depend on it.’
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These findings, which AZTI has been reporting about since 2019, suggest that future ‘refuge areas’ or suitable breeding zones may begin to emerge farther north in northern Europe, Greenland and the Northeast Atlantic.
Out of all of Europe, Spain is the leading producer of bluefin tuna production.
According to APROMAR, Spain harvested 10,877 tonnes of bluefin tuna during 2022, generating an estimated €183.2 million.
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Interestingly, around 96% of the Spanish bluefin production is exported to Japan each year for sushi and sashimi.
But climate change may not only alter where tuna are caught. The environmental shifts could impact the size of the fish, as well.
A 2023 study published in Global and Planetary Change projected a 36% global decline in fisheries productivity, with bluefin tuna expected to lose around 15% of their body mass by 2050.
Given that market prices are typically determined by size, this could potentially reduce the revenue in one of Spain’s most lucrative seafood sectors.
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Each spring as bluefin tuna migrate from the Atlantic into the Mediterranean for mating, fishermen along the coast of Cadiz prepare for a centuries-old tradition: the almadraba season.
The technique was introduced by the Phoenicians 3,000 years ago and includes a complex system of nets placed along migration routes between Barbate, Zahara, Conil and Tarifa.
The fish can weigh more than 500kg, and around 1,6000 tonnes are caught annually using the traditional method.
The almadraba is widely considered a sustainable fishing method. It is also deeply rooted in Andalucia’s cultural identity.
Local dishes such as atun encebollado, mojama, and atun en manteca form part of Cadiz’s culinary heritage, along with the Barbate Tuna Museum that celebrates these practices.
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But if warming waters continue to shift migration routes northward, the question remains: will tuna still pass through the Strait of Gibraltar in the same numbers?
It’s not all bad news, though.
Collaborative research from the Centro Oceanografico de Malaga has already found examples of updating to new fishing methods.
The 2025 study found that Spain’s yellowfin tuna fleet is changing its strategy in the Indian Ocean, adapting to climate-driven shifts and regulatory pressures rather than simply tracking tuna moving forward.
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