• Scientific name: Thunnus thynnus
• Also know as: Tunny, Northern Bluefin Tuna
• Size: Up to 11ft and 1,500lb, but the average adult is around 5ft in length and 550lbs.
• UK minimum size: N/a – protected species that cannot be targeted by anglers.
• UK shore caught record: N/a
• IGFA world record: 1,496lb
• ICUN Status:
  • Global: LC (Least Concern)
  • Europe: NT (Near Threatened)
• Distribution: Found from the Caribbean Sea and along the east coast of the USA and Canada across the whole of the North Atlantic to the north coast of Africa and the whole of the Mediterranean. Although rare they are increasingly sighted in the waters around the British Isles and are present as far north as the colder waters of the Baltic Sea and the Norwegian Sea.
• Feeds on: Fish and squid.
• Description: Oval-shaped powerful body with short fins and long crescent-shaped tail. Small finlets running from dorsal fin to the caudal fin and two dorsal fins are present. The snout is pointed and the mouth is relatively large. Back is dark blue changing to grey on the underside with white dotted lines running upwards from the underside.

Atlantic bluefin tuna is an iconic species across the globe. It is one of the most highly prized food fish in the world, and big game anglers target bluefin tuna due to their prodigious power and fighting qualities. Inevitably, this has led to intensive commercial fishing of this species and a corresponding large scale decline of bluefin tuna across the world. There has been a recovery in Atlantic bluefin tuna numbers since 2010, and a range of factors, which may include warming seas due to climate change, has seen bluefin tuna return to the waters around the UK. The increasing prevalence of bluefin tuna in British waters has led to calls for a catch-and-release recreational fishery to be established, although this has been opposed by conservationists.

Distribution

The bluefin tuna has a very wide distribution due to its migratory patterns. Bluefin tuna are found from the relatively cold waters around the UK and Nordic countries to the warmer waters of the Mediterranean. Their range extends across the Atlantic where they are present from the coast of Canada to the coastline of Brazil and throughout the Gulf of Mexico and the Caribbean Sea. The extent to which tuna populations on each side of the Atlantic Ocean intermix is unclear, but there are two distinct breeding populations in the west and east of the Atlantic Ocean (see below).

Size

There is some dispute over the maximum size Bluefin tuna can grow to. It is generally accepted that they can certainly reach lengths of 12ft and weigh over 1,500lbs (the IGFA world record is just a few pounds short of this weight, see below). However, the US National Oceanographic and Atmospheric Administration states that they can reach 13ft in length and 2000lbs, and the International Union for the Conservation of Nature (IUCN) claim a total length of 458cm (just over 15ft) for this species, although bluefin tuna of this size would be extremely rare. The average size of a fully grown Bluefin tuna is generally 6 – 8ft and between 350b and 550lb in weight.

The largest Bluefin tuna ever caught on rod and line was 1,496lb (678.5 kg). It was caught off the coast of Aulds Cove, Nova Scotia, Canada in 1979 by an angler named Ken Fraser and is accepted by the International Game Fish Association as the all-tackle world record.

Diet, Behaviour and Migration

Tuna is a predatory fish which uses its power and speed to catch fish and squid. Juvenile bluefin tuna will pursue smaller fish such as mackerel, sardines and herring, but as they grow they will chase and catch progressively larger prey, although as they prefer to consume fish which they can swallow whole they avoid the largest species. Bluefin tuna can swim at speeds of up to 40mph and can dive to several hundred metres to find fish to prey on. Bluefin tuna are a highly migratory species. There are two separate breeding stocks, one in the Mediterranean and one in the Gulf of Mexico, although recent evidence points to the potential existence of a third spawning location off the north east coast of the USA. Tuna will therefore undertake long migrations to reach these spawning locations although some Atlantic bluefin tuna may skip a spawning season, meaning they will be found outside of the spawning areas in the summer months.

Use as Food and Overfishing

Bluefin tuna is one of the world’s most highly prized food fish. It is in huge demand in Japan with some reports stating that as much as 75 – 80% of the bluefin tuna which is commercially caught ends up being sold in Japan as sushi or sashimi. In the UK and other western nation’s fresh bluefin tuna is an ultra-premium fish which can command very high prices.

There are two main commercial methods of catching bluefin tuna: long-lines (where lines thousands, of baited hooks are set out at sea and then retrieved after several days) and purse seining (where a vast net is drawn around tuna and then closed). Other methods include commercial fishing for tuna with rod and line which is mostly practised for bluefin tuna by fishermen in US waters, and tuna ‘ranching’ involves catching juvenile tuna and then raising them to fully grown marketable fish in open water fish farms.

Due to the demand for bluefin tuna and the price it can reach this species has been subject to intensive commercial exploitation, and corresponding reductions in stock levels. The IUCN classed bluefin tuna as being Endangered with a declining population trend on a global basis in their 2011 assessment. In the latest assessment which was carried out in 2021, this was changed to Least Concern with an unknown population trend, reflecting the recovery in the numbers of this species. However, in European waters bluefin tuna continue to be classed as Near Threatened, although there is evidence that stocks have recovered slightly since 2010.

Eight European nations (Spain, France, Croatia, Italy, Greece, Portugal, Malta and Cyprus) share the EU quota for bluefin tuna which was set at 15,850 tonnes for 2018. As the UK has no quota for this species UK commercial fishermen and recreational anglers must return any bluefin tuna which are caught to the sea unharmed and as quickly as possible (see the section below). This does not apply to fishermen from EU nations which have a quota for tuna, such as France, who have been able to come into British waters to catch bluefin tuna present there.

This led to the creation of ICCAT (International Commission for the Conservation of Atlantic Tunas) in 1969. This is an intergovernmental organisation which has the task of managing and conserving stocks of tuna and related species in the northern Atlantic and surrounding seas. Unfortunately, ICCAT has developed a poor reputation and has been seen as being responsible for mismanaging stocks and favouring the commercial fishing industry, leading the organisation to be referred to as the International Conspiracy to Catch All Tuna. In recent years the organisation has begun to shake off this negative image. Using drift nets to catch tuna was banned in the EU in 2002, and further measures have led to the increasing numbers of bluefin tuna in European waters since 2010, although this progress could easily be undone if pressure from the commercial fishing industry sees quotas increased.

While bluefin tuna is one of the most valuable fish in the world UK consumers may be more used to skipjack tuna (Katsuwonus pelamis). This is the species which is much more likely to be found in tinned tuna and pre-packaged tuna products. It is a much smaller species (only growing to around 3ft in length) and its rapid growth and high fecundity mean that it is a far cheaper, and also much more sustainable, choice of tuna. Indeed, skipjack tuna is so common that it is sometimes referred to at ‘the rat of the sea.’ The IUCN class skipjack tuna as a species of Least Concern in all of the areas where they have carried out stock assessments.

Are Bluefin Tuna Worth Over £1,000,000?

As bluefin tuna are so important in Japanese culture there is a symbolic auction for the first bluefin tuna of the season every January. This auction was held at the famous Tsukiji Fish Market in central Tokyo (until the market was relocated to a different location in Tokyo in 2018). Prices paid for this tuna can reach incredible levels which thousands of times in excess of the true value of the fish as wealthy Japanese businessmen bid against each other for the honour and the prestige of purchasing the first bluefin tuna of the season.

In January 2019 Kiyoshi Kimura, the owner of a sushi restaurant chain, set a new record paying £2.5 million for a 612lb bluefin tuna. The price paid for these tunas are highly publicised around the world and are then used by poorly-informed media outlets to claim that bluefin tuna is a species where a single fish is worth over a million pounds. This is of course nonsense and although they are a very commercially valuable fish the true market rate of a tuna is only a fraction of the prices paid at the symbolic first tuna Japanese auction of the year. Read more about this in our article on Tsukiji Fish Market by clicking here.

UK Big Game Tuna Fishing and British Record Catch

In the first half of the twentieth century bluefin tuna were relatively common in the North Sea, attracted by the huge shoals of herring which were present. Indeed, in the 1920s and 1930s big game fishing for tuna from Whitby and Scarborough became a fashionable pursuit, attracting the wealthy and famous people of the day to the hotels in the area in the summer and early autumn months.

Multiple tuna over 700lb were caught every year from boats sailing from Scarborough and Whitby from the early 1920s until the outbreak of World War Two in 1939. It was during this time that the biggest ever catch on rod and line from British waters was made when Lorenzo Cecil Vaughan Mitchell-Henry caught an 851lb bluefin tuna when fishing out of Whitby in 1933. This catch is still listed by the British Rod Caught Fish Committee as the largest verified catch in UK waters. In 1947 Bidi Evans caught a 714lb tuna from her father’s yacht off the North Yorkshire coast, a record which still stands as the UK women’s record rod and line-caught fish.

While big game fishing for tuna continued in the post-war years commercial fishing of mackerel and especially herring expanded dramatically. It was the decline of these prey species (and not the tuna themselves) which led to the Scarborough and Whitby big-game tuna fishing eventually winding down in the 1950s, with the last significant large tuna of the North Sea big game fishing era reportedly being caught in 1954.

Read our full article on big game tuna fishing in British waters by clicking here.

Tuna’s Return to British waters

Today there is clear evidence that bluefin tuna are present in the waters to the south and west of the British Isles. The Times reports that there has been over 500 sightings of tuna across the British Isles between 2013 and 2018, and anglers fishing for shark species and commercial fishermen trawling for other species have also inadvertently caught bluefin tuna. In 2018 a 770lbs tuna was caught by a commercial vessel off the coast of Devon, while a 600lb tuna became trapped in a fish pen in a Scottish fish farm but was eventually released by the staff. In the same year a boat angler caught a 500lb, 7ft 7in long bluefin tuna around forty-five miles off the Welsh coast and a “300lb plus” tuna was caught off Plymouth. In summer 2018 a video was posted to YouTube showing tuna breaking the surface in UK waters. The footage was taken from a drone by fishermen targeting porbeagle and blue sharks in an unidentified area off the UK coast. Watch the video by clicking here.

The reasons for the return of tuna are not fully understood. Warming seas due to climate change could play a part, as could the changes in number and movement of small fish which tuna prey on such as herring. Scientists have put forward the idea that the recent increase of bluefin tuna in British waters is due to a phenomenon called the Atlantic Multidecadal Oscillation. This is a naturally occurring long-term change in the temperature of the North Atlantic. Approximately every sixty to one hundred years the Atlantic Multidecadal Oscillation changes from a negative phase (cooler) to a positive phase (warmer). The current positive phase may explain the growing number of tuna in the usually colder waters of the British Isles and Nordic countries. Scientists have warned that the current trend of warmer seas in northern Europe could mean a colder Mediterranean Sea, and it is unknown how this would impact on the spawning patterns of bluefin tuna.

The increasing evidence of tuna returning to the UK has led to scientific research being commissioned to confirm that this species is now present in British waters. Scientists from Cefas (Centre for Environment, Fisheries and Aquaculture Science) and the University of Exeter have started a study which will seek to find out more about the movements and numbers of bluefin tuna in British waters. Funded by Defra and the European Maritime and Fisheries Fund the study began in 2018. Read more here.

Big Game Fishing for Tuna to Return to UK Waters?

While a return to the tuna numbers of the 1920s and 1930s may have seemed far-fetched just a few years ago there are now calls for a big game recreational tuna fishery to be re-established in UK waters. In late 2018 the BBC reported that the Angling Trust joined with Bluefin Tuna UK at Westminster to launch the campaign to have a “properly regulated, science-based, live release UK tuna fishery” off the coast of Cornwall. The North Cornwall MP and keen angler Scott Mann backed the proposal, stating “It would be a massive boost to our coastal communities if the government was to take up these proposals and allow local anglers to enjoy world-class catch and release big game fishing right on our doorsteps.”

One problem which has stood in the way is the complicated way in which protection for tuna in UK waters is tied into EU law. Only the eight EU nations with bluefin quota can catch this species in European waters, leaving British fishermen and anglers in the situation where they cannot catch bluefin in their own waters, but foreign fishermen from eight different European nations can come into British waters to catch this species. Once Britain has left the EU establishing a recreational catch-and-release bluefin tuna fishery could be possible, but even this may require the UK to adhere to international rules which govern Atlantic/Mediterranean tuna fishing.

The current regulations mean that both commercial fishermen and recreational anglers are prohibited from specifically targeting this species and if a bluefin tuna is inadvertently caught it must be returned to the sea alive and unharmed and as quickly as possible. This means that boat anglers who catch a bluefin tuna should not bring it onto the boat to be photographed but should instead unhook and release the tuna while it is still in the water. Sightings of bluefin tuna (including dead tuna) should be reported to either the Marine Management Organisation or Thunnus UK using this link.