The bluefin tuna was once the king of the seas. Living in large shoals and hunting together, Atlantic bluefin are long-lived and highly migratory fish that can be found throughout the Atlantic Ocean. Their only crime is that, to sushi eaters, they taste delicious. Before the 1960s, bluefin tuna was only fished in small quantities; however, demand rose as the fish became a Japanese delicacy and was soon targeted heavily by commercial fisheries.

Now it is on the brink of extinction, having been unsustainably fished for so long.

The causes of extinction

Overfishing: Over the past few decades, numbers of bluefin tuna have declined due to commercial and also unregulated fishing. Illegal fishing of this animal means that no data is kept or analysed, and often even regulated fishery numbers are misinterpreted, making it incredibly difficult to gain the state of bluefin in the wild.

Habitat degradation: Key habitats such as spawning grounds are crucial to species survival. When these fragile locations are hit by pollution and mismanagement, such as the oil spill from Deepwater Horizon in 2010, it can have huge knock-on effects for tuna survival.

Taking young fish: It’s not just taking an excess of fish that is an issue; it’s removing the fish that are too young to have had a chance to reproduce. Bluefin develop slowly, not reaching sexual maturity until five to eight years of age. When juvenile fish are removed from the water, the species has no hope of recovery.

What you can do…

To help save the bluefin, be vigilant about what tuna you eat. Always ask restaurants and fishmongers where they get their fish, and boycott bluefin sourced from the Mediterranean.

Tuna statistics:

• A single bluefin tuna was sold in Tokyo for £1.09 million ($2 million) in January 2013

• 80 per cent of the world’s bluefin tuna is eaten in Japan, where it is known as ‘hon-maguro’ or ‘kuro-maguro’

• Bluefin fishing was banned the Gulf of Mexico in 1982, but fisheries still net tuna as bycatch

• It’s not all bad: bluefin spawning stock in the Mediterranean has nearly doubled since the 1950s

Bluefin in the wild

Two stocks of Atlantic bluefin tuna are present – the east and west populations – although much of their range overlaps in the central Atlantic Ocean.

Why save the bluefin tuna?

Bluefin tuna are warm-blooded, and able to regulate their body temperature – this is very unusual for a fish. The bluefin is as comfortable in the icy waters of Iceland as in the warm waters of its tropical spawning grounds.

These ocean beasts can grow to a whopping two metres (6.6 feet) in length, and can live for up to 40 years. The species grows slowly, and gets to such a large size by hunting other fish, crustaceans and eels voraciously, as well as feeding on smaller oceanic offerings such as plankton.

The bodies of bluefin tuna are incredibly streamlined, and these fish are built for speed. They can even retract their fins to reduce drag, and are capable of reaching speeds of up to 70 kilometres (43 miles) per hour as they dart through the water.

What’s being done?

Alongside educating people about the tuna they eat, wildlife charities and trusts are working with fishermen to manage tuna catches

The key management measures being put in place to protect the Atlantic bluefin involve setting sustainable fishing limits and developing harvest control rules for all main fishing stocks. At the moment, the purse-seine net method of fishing is a major issue; fisheries, particularly those in the Mediterranean, use circular nets that encircle a shoal of fish, and then pull the bottom of the net together to trap them. This catches a huge amount of fish, and although quotas are set, until the fish are landed and counted, the quantity that has been caught is unknown.

Bluefin tuna are now so valuable that illegal, unreported and unregulated (IUU) fishing is rife, and it’s thought that fisheries will often sell on their excess catch and not declare it, or simply not declare their catch at all, rendering the whole process of setting quotas useless.

“Bluefin tuna are now so valuable that illegal fishing is rife”

Groups such as Pew Charitable Trusts and the World Wildlife Fund (WWF) are devoted to saving the bluefin tuna and are working with fishermen and other tuna consumers to bring this fish back from the brink. Their aim is to reduce the amount of tuna taken from the sea, put limits on the size of fish that is removed and to work with fisheries to find different and more sustainable methods of catching bluefin.