Marine Life & Conservation Blogs
Bluefin Tuna Back in UK Waters

Bluefin Tuna are back in the seas around the UK after decades of decline and absence. It has been proposed this could be due to warming seas rather than species recovery. After generations of overfishing, pollution and lack of food, it is astonishing how resilient these Tuna and other species are in their survival and wondrous that they should be able to return at all. What is not so wondrous is human nature. The Angling Trust are now petitioning for the protection status for these fish to be changed to establish a catch and release licensed fishery in what seems to me to be a case of self gratification and financial profit over sensible environmental concern.
New research by Dr Robin Faillettaz from the University of Lille (France), his French co-workers Drs Gregory Beaugrand and Eric Goberville, and Dr Richard Kirby from the UK – as part of the scientific programme CLIMIBIO (www.climibio.univ-lille.fr/) – has revealed that warmer seas can explain the reappearance of tuna around the UK.
Dr Richard Kirby says “Bluefin tuna have been extensively overfished during the 20th century and the stock was close to its lowest in 1990, a fact that further indicates the recent changes in distribution are most likely environmentally driven rather than due to fisheries management and stock recovery. Before we further exploit bluefin tuna either commercially or recreationally for sport fishing, we should consider whether it would be better to protect them by making the UK’s seas a safe space for one of the ocean’s most endangered top fish.”
I asked him for more information and he sent me the following report:
“Bluefin tuna are back in the sea around the UK after decades of absence and a new study says that warming seas can explain why. Bluefin tuna are one of the biggest, most valuable, most sought after, and most endangered fish in the oceans. Sport fishermen excited at the prospect of catching a fish that can grow to over 900kg have already launched a UK campaign to allow recreational fishing for one of game fishing’s top targets. But should we catch and exploit this endangered species or should we make UK waters a safe space for this incredible fish? Important questions to answer are why has this endangered fish suddenly returned to the UK after an absence of nearly 40 years and are bluefin tuna now more abundant or have they just changed in their distribution?
CLIMIBIO’s research shows that the disappearance and reappearance of bluefin tuna in European waters can be explained by hydroclimatic variability due to the Atlantic Multidecadal Oscillation (AMO), a northern hemisphere climatic oscillation that increases the sea temperature when in its positive phase like it is now.
To come to their conclusion, the scientists examined the changing abundance and distribution of bluefin tuna in the Atlantic Ocean over the last 200 years. They combined two modelling approaches, focusing on the intensity of the catches over time and on the distribution of the fish’s occurrence, i.e. when it was observed or caught. Their results are unequivocal: the AMO is the major driver influencing both the abundance and the distribution of the bluefin tuna.
The Atlantic Multidecadal Oscillation affects complex atmospheric and oceanographic processes in the northern hemisphere including the strength and direction of ocean currents, drought on land, and even the frequency and intensity of Atlantic hurricanes. Approximately every 60 to 120 years the AMO switches between positive and negative phases to create a basin-scale shift in the distribution of Atlantic bluefin tuna. During a warm AMO phase, such as since the mid-1990s, bluefin tuna forage as far north as Greenland, Iceland and Norway and almost disappear from the central and south Atlantic. During its previous warm phase – at the middle of the 20th century – the North Sea had a bluefin tuna fishery that rivalled the Mediterranean and the Bluefin Tunny sportfishing club – known worldwide – was founded in Scarborough. However, during a cold AMO phase, such as that between 1963-1995, bluefin tuna move south and are more frequently found in the western, central, and even southern Atlantic, with few fish caught above 45°N. Dr Faillettaz says that “The ecological effects of the AMO have long been overlooked and our results represent a breakthrough in understanding the history of bluefin tuna in the North Atlantic.”
In fact, the most striking example of the effect of the AMO on bluefin tuna is the sudden collapse of the large Nordic bluefin tuna fishery in 1963. The collapse coincides perfectly with the most rapid known switch in the AMO from its highest to its lowest recorded value in only two years. After that switch tuna also vacated the North Sea, and the conditions remained unfavourable for bluefin tuna in the northern Atlantic until the late 1990s when it started to reappear around the UK.
The scientists expect that bluefin tuna will continue to migrate to the UK and North Sea waters every year until the AMO reverses to a cold phase. However, they also highlight that the additional effect of global warming on sea temperatures will make the future response of bluefin tuna to changes in the AMO uncertain. Further to the effect of the AMO on where and when bluefin tuna occur in the Atlantic, the study also found that this climatic oscillation influences their recruitment, i.e., how many juvenile bluefin tuna grow to become adults.
Dr Faillettaz said that “when water temperature increases during a positive AMO, bluefin tuna move further north. However, the most positive phases of the AMO also have a detrimental effect upon recruitment in the Mediterranean Sea, which is currently the most important spawning ground, and that will affect adult abundance a few years later. If the AMO stays in a highly positive phase for several years, we may encounter more bluefin tuna in our waters, but the overall population could actually be decreasing.”
Consequently, Dr Beaugrand warns that “global warming superimposed upon the AMO is likely to alter the now familiar patterns we have seen in bluefin tuna over the last four centuries. Increasing global temperatures may cause Atlantic bluefin tuna to persist in the Nordic region and shrink the species distribution in the Atlantic Ocean, and it may even cause the fish to disappear from the Mediterranean Sea, which is currently the most important fishery.”
Dr Goberville also raises another important observation saying that “because bluefin tuna are so noticeable, they are also an indicator of current temperature driven changes in our seas that are occurring throughout the marine food chain, from the plankton to fish and seabirds”.
The Atlantic bluefin tuna fishery indeed encompasses most of the problems seen in fisheries around the world, including fleet overcapacity and political mismanagement; the species’ distribution crosses exclusive economic zones and spans international, open-access waters (i.e. the entire North Atlantic, from the Mediterranean Sea to the Gulf of Mexico). Added to that, the long-term fluctuation in Atlantic bluefin tuna abundance was hitherto understood poorly, which represents a fundamental gap in this fish’s sustainable management.
Dr Kirby says that “we have shown why bluefin tuna occur when and where in the North Atlantic and what may influence their recruitment and abundance, and this is fundamental to understanding the management of a fish that is endangered due to overfishing. Bluefin tuna have been extensively overfished during the 20th century and the stock was close to its lowest in 1990, a fact that further indicates the recent changes in distribution are most likely environmentally driven rather than due to fisheries management and stock recovery.”
Before we further exploit bluefin tuna either commercially or recreationally for sport fishing, we should consider whether it would be better to protect them by making the UK’s seas a safe space for one of the ocean’s most endangered top fish.”
The lead author Dr Faillettaz concludes: “Our results demonstrate that local changes in Atlantic bluefin tuna abundance can reflect large-scale shifts in a species’ distribution that are unrelated to improvements or worsening of a stock’s abundance. In this context we hope that our study will highlight the need to consider the environment when planning the sustainable management of all migratory fish species.”
For further information
Dr Richard Kirby
E-mail: Richard.Kirby@planktonpundit.org
Dr Robin Faillettaz
E-mail: Robin.Faillettaz@univ-lille1.fr
For further reading
Could big-game fishing return to the UK?
Warming Seas linked to bluefin tuna surge in UK waters
Blogs
The Ocean Cleanup Launches 30 Cities Program to Cut Ocean Plastic Pollution from Rivers by One Third by 2030

The Ocean Cleanup, the international non-profit with the mission to rid the world’s oceans of plastic, has announced, at the UN Ocean Conference (UNOC), its plan to rapidly expand its work to intercept and remove ocean-bound plastic pollution.
The 30 Cities Program will scale the organization’s proven Interceptor™ solutions across 30 key cities in Asia and the Americas, aiming to eliminate up to one third of all plastic flowing from the world’s rivers into the ocean before the end of the decade.
This evolution follows five years of learning through pioneering deployments across 20 of the world’s most polluting rivers and represents a key next step in the organization’s mission and the global fight against ocean plastic pollution.
With the 30 Cities Program, The Ocean Cleanup will transition from single river deployments to citywide solutions, tackling the main plastic emitting waterways within each selected city. This follows a key learning from deployments in Kingston, Jamaica, which showed it is possible to scale faster when projects encompass whole cities, as the same set of partners can be involved with all deployments.
To date, The Ocean Cleanup has already prevented 29 million kilograms of trash from reaching the ocean. The organization currently intercepts an estimated 1–3 percent of global river-borne plastic emissions. With the first 20 river deployments close to being fully operational, it is now poised to reduce the plastic pollution flowing into the ocean from rivers by up to a third.
“When we take on an entire city, instead of individual rivers, we can scale faster, reduce costs, and maximize impact,” said Boyan Slat, Founder and CEO of The Ocean Cleanup. “Our analysis shows that strategically deploying Interceptors across just 30 carefully chosen cities can stop up to a third of river plastic pollution worldwide. This is the next big leap toward our ultimate goal of a 90 percent reduction in global ocean plastic pollution.”
City-by-city: a Faster Path to Scaling
Using the latest scientific modeling and on the ground experience, The Ocean Cleanup identified 30 major plastic polluting coastal cities which include:
• Panama City, Panama – First deployment to go live in the coming months.
• Mumbai, India – Mapping of all waterways completed; preparations for first deployments underway.
Furthermore, the organization is developing plans to expand on its existing work to all polluting rivers in:
• Manila, Philippines; Montego Bay, Jamaica; Jakarta, Indonesia; Kuala Lumpur, Malaysia; Bangkok, Thailand and Los Angeles, U.S.A.
Other cities will be announced once the necessary partnerships and agreements are in place. Planning and fundraising activities are underway for all 30 cities. To realize these ambitious plans, the organization is currently also expanding its engineering and operational capacity.
Data Driven Restoration at Scale
Before Interceptors are deployed, each city project begins with an intensive analysis phase. Aerial drones, AI-powered image analysis, and GPS-tagged “dummy” plastics are used to chart every visible waterway and track how waste moves from streets to sea. These real-time insights guide optimal Interceptor placement and provide a public baseline against which progress can be measured.
Alongside intercepting new plastic, the 30 Cities Program will also remove debris from nearby coasts, mangroves, and coral reefs. This twin-track approach—shutting off the tap while clearing the legacy pollution—enables The Ocean Cleanup to achieve long-term impact, which includes the restoration of fish nursery habitats, boosting coastal tourism, and strengthening of natural storm surge defenses for local communities. Alongside local partners, the organization also advocates for improvements in waste management and awareness raising amongst communities.
Completing the First 20 Rivers
While laying the foundation for the 30 Cities Program, The Ocean Cleanup is also nearing completion of its first 20 river projects. The next landmark achievement—expected as soon as the second half of this year—is in the western Caribbean, where the team aims to resolve the plastic pollution problem in the Gulf of Honduras by intercepting the trash feeding into this body of water.
A Stepping Stone Toward a 90 Percent Reduction
The 30 Cities Program represents the first major scaling step in The Ocean Cleanup’s journey to eliminate 90 percent of floating ocean plastic pollution. In parallel, efforts are continuing to remove plastic from the Great Pacific Garbage Patch. Whilst extraction operations are currently on hiatus, work to deploy cutting edge technologies to map the “hotspots”, or areas of intense plastic accumulation, in order to make future extractions more efficient and economical, is ongoing.
By combining river interception and coastal cleanup with its offshore cleanup systems targeting legacy pollution that’s already in the ocean, the organization is charting a path to turn off the tap and mop up the mess.
About The Ocean Cleanup
The Ocean Cleanup is a nonprofit organization that develops and scales technologies to rid the oceans of plastic. By conducting extensive research, engineering scalable solutions, and partnering with governments, industry, and like-minded organizations, The Ocean Cleanup is working to stop plastic inflow via rivers and remove legacy plastic already polluting the oceans. As of June 2025, the non-profit has collected over 28 million kilograms (62 million pounds) of trash from aquatic ecosystems around the world. Founded in 2013 by Boyan Slat, The Ocean Cleanup now employs a multi-disciplined team of approximately 200 people. The organization is headquartered in Rotterdam, the Netherlands, with international operations in 10 countries. For more information, visit www.theoceancleanup.com.
Blogs
Rescues, Rays, and Darwin the Turtle: My Trip to Biomes Marine Biology Center

It’s time to catch up with 12-year-old Mia DaPonte, New England’s youngest ever female PADI Master Scuba Diver, in her latest blog for Scubaverse!
It’s still a little too cold to get in the water here in New England. I wish I had a drysuit! To get my ocean fix, I asked my mom to take me and my friends to the Biomes Marine Biology Center.
What is Biomes? It’s a rescue center near my house that’s home to all kinds of ocean animals—and they’re all local! It’s truly awesome to experience. There are so many cool creatures there, like skates, sharks, stingrays, horseshoe crabs, tropical fish, lobsters, seahorses, octopuses, and even some reptiles that were given up by their owners.
Darwin the turtle is always fun to watch. He’s huge and has his own home, but he also gets to wander around the place on his own when he feels like it!
They have lots of touch tanks. I got to touch sharks, turtles, and even hold a horseshoe crab! (There’s a little lip on the side of their shell where you can hold them—but don’t do this without permission! Their gills always need to stay in the water.) I also touched stingrays! They felt slimy but rough at the same time.
One of my favorite things to do is see the octopus and watch it play with the toys in its tank. I always check to see if any seahorses are pregnant and look for the babies when they’re born. The babies are kept in their own tank at first to stay safe, and then moved when they’re big enough.
We got lucky this time—there was a baby skate in a mermaid’s purse that was ready to hatch any day! It was in a special tank with a light. When you press the button, the light turns on so you can see the baby skate moving around inside the purse!
As our visit was ending, the owner, Mark, sat down with us and told us how he started Biomes. When he was 14 years old, he began rescuing sea animals. His love for the ocean started when he was young—just like mine! As he got older, he started a traveling business, bringing animals to classrooms and doing shows. Eventually, he turned it into something bigger, and now Biomes is a huge center full of rescued animals.
He told us that most of the fish and animals are rescued from fishing boats or the cold waters of New England—places where tropical fish wouldn’t survive the winter. They try to rescue babies whenever they can, so they have a better chance of adapting. Darwin the turtle actually hatched in Mark’s hand!
My mom gets a pass to Biomes every year because I love going there so much. There are always new animals to see and feedings to watch. One time, I even got to feed the octopus!
If you ever come to Rhode Island, you have to check out Biomes!
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