Many of us will be familiar with the different species of tuna that are traded internationally in cans, fresh, frozen steaks and sushi. However, the importance of tuna is far greater than as a filling in a sandwich with mayo.
Fishing for tuna is carried out in the tropical and sub-tropical waters of the world where the fish migrate around all of the world’s oceans. The different species of tuna all have different characteristics: size, weight, sexual maturity, the number of eggs laid, how deep and where they swim.
Some tuna species like the Bluefin tuna are majestic animals. They can reach up to 4 metres long and weigh near to 680kg – that is heavier than a horse! While most fish are cool-blooded, Bluefin tuna are almost like warm-blooded animals (just like you and me) as their body temperature is higher than the surrounding sea water.
Their warm bodies allow them to swim very fast, to nearly 15km per hour, so that they can chase their prey or avoiding a hungry shark. They are also great adventurers because they travel across the oceans; from US to Japan in the Pacific and from Europe to US in the Atlantic.
Human impacts on Tuna
Catching tuna for human consumption has unfortunately had some dramatic impacts. Some of the tuna fisheries now have very low numbers such as the Southern Bluefin tuna stock or the Eastern Atlantic Bluefin tuna stock which are highly valued for sushi. Last year one fish sold for £1 million – these stocks are classified as ‘Critically Endangered’ and ‘Endangered’ (respectively).
Other species such as the Skipjack are more fortunate because they have much bigger populations, and even though it is fished quite heavily, due to its biological characteristics it is less vulnerable to over-exploitation. They are much smaller, faster at growing and reproducing and of lower value – so for these reasons it is found in our cans.
In addition to these there are also the Yellowfin, Bigeye and Albacore tuna which can be found in our shops. Each species has stocks in different parts of our oceans and has different levels of pressure. Because of this reason, stock for each species needs to be considered under separate assessments to determine if it is sustainable or not.
Most of the tuna that we eat comes from fisheries that are in the middle of the ocean (high seas) or are a good way from the shore – I would be surprised if you were to stand with a rod on the shore and ever catch a tuna! Therefore you need a boat.
Vessels that catch tuna
Around the world, vessels that catch tuna vary greatly from huge ‘purse-seine’ vessels and industrial ‘longliners’ to small artisanal vessels that land into local markets. Often the large vessels travel thousands of miles for many days across the oceans to rich fishing grounds or to transport the catch to factories. For island states such as those in the Pacific and Indian Oceans fishing for tuna provides jobs and income to thousands of people.
For remote island nations tuna fisheries contribute millions of dollars to their Gross Domestic Product (GDP) and employ thousands of fisher-folk. In the Western Central Pacific where more than half of the total global tuna occur, the determination for collaborative management to protect this important natural resource has led to the creation of the Parties to the Nauru agreement (PNA).
Third party certification
Eight island nations are party to the PNA and within their jurisdiction have approximately a quarter of the world’s tuna catch. Similarly the Maldives have also worked very hard to manage their pole and line tuna fishery. The free-school skipjack fishery and the pole and line skipjack fishery have managed to achieve the highest standard of sustainable certification available to a fishery, the Marine Stewardship Council (MSC). Unfortunately not many of the world’s tuna fisheries have managed to achieve this certification yet, but hopefully there will be more in the future.
What we’re doing to help
WWF encourages the seafood industry to improve fisheries to the MSC standard so that this will ensure the sustainability of tuna stocks, the balance of the ecosystem and the livelihoods for those dependent upon it – far into the future. We’re working at the national level trying to ensure that UK companies are sourcing responsibly and are investing in projects that will improve the sustainability of the tuna fisheries. We are also supporting our colleagues in the tropics who are working at the regional and international level, generating improvements to fishing regulations that will support the sustainable management and exploitation of this highly important species.
What you can do to help
Look for the blue MSC logo when you choose your favourite canned tuna or sandwich so that you know they come from sustainable tuna fisheries.
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