Wildlife

Tuna survival on the line

Réunion island tuna

Photo credit: Yoann Jezequel

Now that everyone has left the comfortable cocoon of their mother’s cooking and a fridge stocked full of groceries again, it is time for freshers and returning students alike to once again start foraging for themselves. I’m not a vegetarian myself, and this is not going to be an article preaching for you to clear your fridge of all meat Products, but I would just like to make you consider that buying tuna is the ecological equivalent of putting a can of panda in your Tesco shopping basket.

Conservation charities such as the World Wildlife Fund (WWF) and Greenpeace catch the public’s attention by using the faces of fluffy mammals with big eyes to mournfully stare down the camera and capture the hearts of animal lovers, which is important for persuading people to choose environmental causes over all the other worthy charities out there, but it skims over many of the other beautiful faces in the animal kingdom which also need a voice.

Tuna? Beautiful? Most people may never have actually seen tuna in any other form than the pink fringes peeking out of paninis and buried in pasta sauces, but actually there is a raw beauty to be seen in fish, as anyone who has ever been diving or snorkelling will be able to attest to. Just because the underwater world is so different from our own, people find the grace and majesty of its underwater inhabitants difficult to identify with and stories of overfishing and plummeting fish populations have much less emotional impact than the lone polar bear perched on a tenuous, melting iceberg.

But tuna actually have a fascinating biological background that easily competes with the adorable faces of Tian Tian and Yang Guang (Edinburgh’s celebrity pandas). Like all members of the tuna family, bluefin tuna are actually warm-blooded. This is is more well developed in bluefin than in any other fish, allowing them to hunt in the deep, cold waters of the Arctic. Not only this, but bluefin tuna are incredible predators that rival great whites in their decimation of the smaller fish populations- a vital role in the ocean ecosystem, especially as their great migrations take them across the Atlantic ocean, affecting fish populations all over the globe.

Their hunting strategies add to the dark majesty of these aquatic apex predators, as they work together with dolphins and shearwater seabirds to attack huge swarms of smaller fish. Their prey, fish such as mackerel, unite together to form a whirlpool mass of shimmering silver to defend themselves, a formation scientists have called ‘baitballs’. The predators that stalk these shadowy swarms join forces to hunt their prey- dolphins releasing cascades of bubbles to
create an elemental net of air around the mackerel. The bluefin slice through the baitball like knives, splitting their prey into skittish shoals that all the predators can feast on. As they are driven up to the surface, shearwater seabirds chase the baitball from above, breaking the surface to fly through the water and scoop up their share.

Unfortunately, this collaboration between mammal and fish means that one of the most serious consequences of tuna overfishing is bycatches. Even if you disagree with my view on the majesty of these sea kings, you may consider reducing your tuna consumption for the effect it may have on leatherback turtles, sharks, albatrosses and their partners-in-crime, dolphins. Tuna have been fished sustainably for thousands of years, but in the last century there has been a 90 per cent decline in tuna populations, causing the International Union for Conservation of Nature (IUCN) to grant them Endangered Species conservation status alongside tigers, blue whales, snow leopards and giant pandas.

Due to the demand, which is especially high in the Japanese sushi markets, and the lack of awareness, this problem is only getting worse. Professor Barbara Block from Stanford University, a marine biologist who has spent the greater part of her career researching this species and working for their conservation, said in a TedTalk to spread awareness, “Bluefin are pursued wherever they go. There is a gold rush on Earth and this is a gold rush for tuna. There are traps that fished sustainably up until recently. And yet the type of fishing going on today with pens, with enormous stakes, is really wiping bluefin ecologically off the planet.”

So think of this next time you think of reaching for a can of tuna: bluefin tuna can grow up to four metres (about the length of a Land Rover), can live up to twenty years, spend all their lives crossing oceans in epic odysseys, have a vital role in underwater eco-systems and should be treated with the same conservation status as chimpanzees, African penguins and gorillas.

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