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Bluefin Tuna Back in UK Waters

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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

Calls to fish endangered bluefin tuna

Giant tuna causes ‘frenzy’ at salmon farm

Jeff is a multiple award winning, freelance TV cameraman/film maker and author. Having made both terrestrial and marine films, it is the world's oceans and their conservation that hold his passion with over 10.000 dives in his career. Having filmed for international television companies around the world and author of two books on underwater filming, Jeff is Author/Programme Specialist for the 'Underwater Action Camera' course for the RAID training agency. Jeff has experienced the rapid advances in technology for diving as well as camera equipment and has also experienced much of our planet’s marine life, witnessing, first hand, many of the changes that have occurred to the wildlife and environment during that time. Jeff runs bespoke underwater video and editing workshops for the complete beginner up to the budding professional.

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Can reef conservation be both enjoyable and profitable?

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wakatobi

At Wakatobi Dive Resort, guests are always thanked for coming to enjoy this special place, as it is their presence that creates the magic making ongoing reef conservation efforts a reality. “The more you know, the more you notice,” says in-house marine biologist Julia Mellers. “And what better place to learn about reef biodiversity and custodianship than in Wakatobi.”

“My main project for the first year is to establish a way of monitoring the health of Wakatobi’s reef ecosystem,” Julia says. “This will allow us to provide hard scientific proof that Wakatobi’s conservation model measurably benefits reef health. Holding a finger to the pulse of the reef will also assist management decisions, such as identifying priority areas for increased protection.”

Modern methods for reef management

The Wakatobi Reef Health Assessment program utilizes a customized set of modern imaging and data analysis techniques that provide a comprehensive indication of the state of a reef ecosystem. “We use the latest ecological theory, technology, and artificial intelligence to develop a novel package to efficiently and robustly measure reef health,” Julia says. “This will enable us to monitor how Wakatobi’s reefs are faring throughout the protected area without significantly diverting resources from protecting the reefs.”

The process begins in the water, capturing the reef’s sights, sounds, and landscape. Above water, Julia is developing and implementing analysis methods and training machine learning models to extract measures of reef health from captured data. When not on the island, she will research new approaches and ideas for coral reef assessment and help spread the word about Wakatobi’s scientific initiative.

“It’s an absolute privilege to work within a system that benefits both the reefs and the local people,” says Julia. “It also gives us a unique opportunity to assess and document reef health and dynamics within an ecosystem that is actually getting healthier. In stark contrast to declines in coral health recorded elsewhere, our scientific data is already beginning to demonstrate Wakatobi’s astonishing biodiversity – which is evident to anyone who ventures underwater at the resort.”

The program focuses on three indicators of reef health: the diversity of the reef community, which measures the variety and abundance of living organisms colonizing the reef surface; structural complexity, describing the degree to which the reefs incorporate elaborate details; and reef soundscapes, recording the noise a reef’s inhabitants make, including the snapping of shrimp and the feeding sounds of fish. By measuring these elements, it is possible to estimate how much life the habitat supports.

“Luckily, we don’t have to work all that out manually,” Julia says. Artificial intelligence plays a vital role. “I train machine learning models to identify signals of reef functioning that would otherwise be undetectable. For example, a model can be trained to recognize the sounds that characterize a healthy reef. This allows us to monitor the reefs at a scale, and with a thoroughness that would otherwise be inconceivable.”

Julia and the dive team have also started an eDNA survey of the reefs. ”This involves taking seawater samples near the reef at different depths and filtering them to trap environmental DNA (eDNA) that organisms shed into the water,” Julia explains. “The samples are now in a lab, where the DNA is labeled using probes and sequenced to identify which species are around. Using this technique, we should be able to detect hundreds of species from just a single litre of seawater. It’s a very cool process!”

wakatobi

A Wakatobi welcome

Julia says the Wakatobi team has been exceptionally supportive and welcoming. “They are able to maintain a totally laid-back atmosphere while coordinating an exceptionally professional operation.” She adds that Wakatobi feels remote in the best ways, with pristine reefs, peace, and quiet, while also being an extremely comfortable and well-connected place to work.

“Working within a system that works for the reefs because it works for the people is an absolute privilege,” she says. “It also gives us a unique opportunity to unpick reef health and dynamics within an ecosystem that is actually getting healthier. In stark contrast to declines recorded elsewhere, our scientific data is already beginning to demonstrate the astonishing biodiversity evident to anyone who ventures underwater at Wakatobi.”

The Wakatobi team has also proven to be an invaluable source of knowledge about the local ecosystem,” Julia says. “Wakatobi makes the perfect scientific laboratory. Being able to go from library to laptop to reef, all in the space of a hundred meters, is the perfect recipe for generating new ideas and trying them out. It is so exciting to work with open-minded innovators keen to try novel approaches and look at things from different angles.”

“Having such a dynamic team has meant that we’ve made progress quickly,” Julia says. “So far, we have a highly accurate machine learning model that classifies the reef community, a method to analyze the sounds that reef critters make, and a fully automatic way of measuring fish abundance. We are also in a position to add to this repertoire, trialing different techniques to quantify the complex 3D structure that corals make. We have added DNA analysis to the arsenal, which enables us to detect biodiversity invisible to the naked eye.”

From frogs to frogfish

Julia acquired her love of nature and biology from her parents, whom she describes as eco-friendly before the concept became trendy. “Camping, compost heaps, and Attenborough documentaries were features of a nature-centric English childhood. I raised pond-dwelling critters, peered down microscopes, and became transfixed by cephalopods.” Biology was an inevitable choice, she says, and the sea came into her life at a young age. “Having long been a sailor, with a family of sailors, I am at home at sea,” she says. “I took my first sip of compressed air at the bottom of a swimming pool in London and have spent as much time as possible eye-to-eye with octopuses since.”

After completing an undergraduate degree in biology at Oxford University, Julia shifted her Master’s focus to marine biology. It was a move she describes as swapping frogs for frogfish. “I went into marine biology because I see marine biological research as a powerful tool to connect people with the planet,” she says. “Of course, nature should be worth more to us preserved than destroyed – but if you can’t put a price on it, no one pays. Wakatobi has created an economic engine that financially incentivizes reef custodianship. This leads to an ideal scientific setting – demonstrably vibrant reefs linked to genuine socio-economic fairness.“

Julia’s Master’s project was done in collaboration with the Australian Institute of Marine Science and investigated mysterious bare rings of sand that surround reef patches within algal meadows. “We think these ‘reef halos’ form because foraging fish will only venture a short way from the shelter of a coral patch if they are under threat from patrolling sharks,” she says. “Since you can spot these halos from satellite images, they could be a neat way of keeping an eye on shark populations from space… and a possible addition to Wakatobi’s monitoring program”!

As the Reef Health Assessment program progresses, Julia will create new learning and participation opportunities for guests to enhance the depth and enjoyment of their Wakatobi experience. Wakatobi Dive Resort will also continue to provide updates and insights on the important work Julia and the rest of the Wakatobi team are doing to understand and protect some of the world’s most pristine and spectacular coral reefs.

Many thanks go to Wakatobi’s guests, whose continued enjoyment of the marine preserve helps keep ongoing reef protection efforts a reality!

Contact the team at office@wakatobi.com or enquire >here.
Follow on Facebook and Instagram.
View Wakatobi videos on the YouTube Channel.

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Get ready for the Marine Conservation Society’s annual Great British Beach Clean this month

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Great British Beach Clean

The programme is one of the largest marine citizen science activities of its kind in the UK. Volunteers taking part will not only be clearing our beaches of litter, but help the Marine Conservation Society, the UK’s leading ocean membership charity, to gather vital data to create change for cleaner and healthier seas.

This year’s Great British Beach Clean is being sponsored by Ireland’s leading soup brand, Cully & Sully Soup, whose support is helping to raise awareness of marine litter and protect UK beaches from pollution.

To sign up for a beach clean, or organise your own, simply visit the charity’s website.

Great British Beach Clean

Key stats and facts

  • At last year’s Great British Beach Clean, 5,416 volunteers conducted 428 beach cleans over 10 days, surveying 64,139 metres of coastline. A total of 129,391 pieces of litter were collected, filling 1,426 bags and weighing 7,476 kg.
  • The Marine Conservation Society has recorded an average drop of 80% in carrier bags found on UK beaches since charges were introduced, showing that policies to reduce plastic work.
  • Data collected during the Great British Beach Clean contributes toward the charity’s annual State of our Beaches report. Last year’s report recorded a 14% increase in drinks-related litter.
  • The report also showed that nine out of 10 beach litter items found on beaches by Marine Conservation Society volunteers last year were made from plastic.
  • Sewage plays a large part in the pollution problem. In 2023, over 29,500 sewage-related items, including more than 21,000 wet wipes, were recorded across the UK and Channel Islands, with sewage-related items present on 72% of surveyed beaches.
  • Data from the Marine Conservation Society’s Great British Beach Clean contributes to a global database, International Coastal Cleanup.

Great British Beach Clean

Key messages:

  • Data collected by volunteers during the Great British Beach Clean shows the positive result of policies like carrier bag charges, and how they work to reduce litter on our beaches.
  • Plastic still remains the most common form of beach pollution – highlighting the urgent need for further action to tackle the single-use plastic problem such as charges, bans and deposit return schemes.
  • The Marine Conservation Society is calling for governments across the UK implement world-class deposit return schemes for drinks containers including glass, plastic, and cans, without any further delay. Currently the proposed scheme is set to start in October 2027, but with Wales being the only country to include glass.
  • The charity hopes that the recent bans on single-use plastics, such as cutlery, will lead to a noticeable reduction in the amount of single-use plastic cutlery polluting our beaches, much like the positive impact of the carrier bag charge.
  • Sewage-related pollution, such as period products and wet wipes, are still prevalent on our beaches. Governments of the UK must turn the tide on pollution and end untreated sewage damaging our marine environment.
  • You can support the charity by helping to clean up the UK’s beaches and collecting valuable data that supports efforts to address sewage pollution effectively.

Great British Beach Clean

ON THE DEPOSIT RETURN SCHEME:

Lizzie Price, Beachwatch Manager at the Marine Conservation Society: “It’s fantastic to see real-world evidence of the effectiveness of policies such as carrier bag charges in tackling pollution from single-use plastics. There’s no denying that these measures have helped to reduce litter on our beaches. However, we cannot afford to become complacent.

“Drinks-related litter, such as bottles and cans, were found on 97% of UK beaches surveyed last year. We need wider policies such as charges, bans, or deposits on more single-use items where possible, including the proposed deposit return schemes for plastic bottles, cans, and glass. We must keep moving towards a society that repairs, reuses, and recycles.”

Great British Beach Clean

ON SEWAGE POLLUTION:

Rachel Wyatt, the Marine Conservation Society’s Water Quality Policy & Advocacy Manager:

“Our seas cannot sustain the deluge of sewage that is being dumped into our waterways on a weekly basis. Our beach clean volunteers find thousands of sewage-related litter items washed up on the beaches every year, but it’s not just physical pollution that is harmful to us and marine life. Raw sewage contains a cocktail of bacteria, viruses, harmful chemicals, and microplastics which is a disaster for our ocean. Governments of the UK must turn the tide on pollution and end untreated sewage damaging our marine environment, so that we can all enjoy sewage-free seas.”

Great British Beach Clean

ON VOLUNTEERING:

Clare Trotman, Beachwatch Officer at the Marine Conservation Society, said: “The work we do at the Marine Conservation Society simply wouldn’t be possible without the dedication of our volunteers, who help gather crucial beach litter data. This information is invaluable in shaping scientific understanding and driving the changes needed to protect our precious marine environment.

“With beach cleans taking place all over the UK and Channel Islands, there are countless opportunities to get involved and support us this year. And if you can’t make it to the beach, you can still contribute by organising a local litter pick and survey in your area.”

Cully Allen from Great British Beach Clean sponsor, Cully & Sully Soup, said: “We are excited to be part of the UK’s biggest beach clean initiative for a third year. As a B Corp, doing good is at the core of what we do. We are always striving to do better internally as a business, but we really enjoy when we get to encourage and join our customers in doing good. We are looking forward to getting stuck into the beach cleans again this year, serving up our soup to the SOUPer volunteers and taking direct action on marine litter.”

Great British Beach Clean

The following beach cleans are currently set to take place:

Date Region County Beach & link
20/09/2024 Weston-Super-Mare North Somerset, England Uphill Beach
20/09/2024 Wirral Cheshire, England West Kirby Beach
21/09/2024 Weston-Super-Mare North Somerset, England Sand Bay Beach
21/09/2024 Cramond Edinburgh, Scotland Cramond Beach
21/09/2024 Aberdeen Aberdeenshire, Scotland Aberdeen City Beach
22/09/2024 Formby Merseyside, England Formby Beach
23/09/2024 Portsmouth Hampshire, England Southsea Beach
25/09/2024 Littlehampton West Sussex, England Littlehampton East Beach
27/09/2024 Swansea Glamorgan, Wales Swansea Beach
27/09/2024 Portstewart Londonderry, N. Ireland Portstewart Beach
27/09/2024 Cleethorpes Lincolnshire, England Cleethorpes Beach
27/09/2024 Brixham Devon, England St Mary’s Beach
28/09/2024 Rhoscolyn Isle of Anglesey, Wales Borth Wen Beach
28/09/2024 Charmouth Dorset, England Charmouth Beach
29/09/2024 Wallasey Merseyside, England New Brighton Beach

Find more information about the Marine Conservation Society at www.mcsuk.org.

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