Bluefin tuna were fished almost to the point of extinction, with no sightings recorded anywhere around the UK for more than 60 years, so their return to the waters of the Southwest is a great source of hope.
These stunning fish, up to 2m long, leap out of the water like dolphins – a spectacular sight that can even be seen from the shore. Their distinctive metallic blue colour mimics sunlight on sea water and serves as camouflage to their predators, the sharks, orcas and pilot whales that feed on them.
Bluefin are one of the fastest fish in the sea swimming over 40 miles per hour. They can live for more than 20 years. But due to their size they can never stop swimming, as they need the constant movement of water over their gills to obtain oxygen, they even sleep on the move.
Tuna are exceptional in being able to regulate their body temperature – most fish are cold-blooded and have the same body temperature as the surrounding water. Tuna generate body heat from their fast swimming, and store the heat in special blood vessels. This allows them to migrate thousands of miles into colder waters.
Yet bluefin start life as tiny larvae, a few millimetres long, in their nursery waters of the Mediterranean Sea. The larvae cannot control their body temperature and with rising sea temperatures in the Mediterranean due to climate change their recovery may be short-lived.
When they are one year old and mature enough to maintain their body temperature, bluefin swim out into the Atlantic and grow to be top ocean predators. Herein lies another problem in that animals at the top of a food chain accumulate chemicals, plastics and heavy metals like mercury from our polluted waters. These persist in the meat that people consume.
In 2023, the UK Government permitted the first trial of commercial fishing of bluefin tuna in 60 years, licensing 10 boats to catch 39 tonnes, amounting to a few hundred tuna. More bluefin will be caught as bycatch in other industrial fishing and in poorly controlled international waters.
Mark Spencer, Minister for Food, Farming and Fisheries, has called for fisheries to diversify their catches to bluefin tuna due to the current fishing bans on pollack. Carli Cocciardi of the Devon Wildlife Trust disagrees, “We should be investigating and resolving the cause of the crash in pollack stocks and seeking sustainable approaches to fishing, rather than simply moving our attentions to bluefin as the next fishing opportunity.
“Otherwise, the return of the spectacular bluefin to our waters could be very short lived indeed.”
Fish are too often seen simply as a food resource to be exploited. Economic gain is allowed to override the conservation and management needed to ensure the long-term survival of these wild animals and the protection of complex marine ecosystems. Overfishing has caused the loss of bluefin from our waters once. We must not allow bluefin to disappear again.