Ask anyone for a list of five fish species and there’s likely to be a tuna among them. This fame is of course not entirely unrelated to the fact that we consume it in rather large quantities, which has led to a serious decline in tuna stocks around the world (making the old nickname “common tunnyfish” somewhat less fitting nowadays). What few people realise, however, is that the tuna is one of the top predators of the oceans, right up there with the big sharks and toothed whales.

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The giant bluefin tuna

To be fair, orca’s and white sharks do eat tuna every now and then, but there’s few who would dare to take on a shoal of fully grown tunnyfish. Reaching lengths of 3 metres or more and easily weighing well over 450 kilos, the adult tuna strikes fear in the hearts of ocean dwellers everywhere, including the much smaller mackerel, to which it is closely related. What is most striking about the tuna is its ability to swim across oceans almost continuously at fairly high speed. While most fishes make a wavy motion with their bodies in order to propel themselves, a tuna keeps its body and fins almost entirely stiff, slashing only its crescent-shaped tail fin through the water, making it one big streamlined forward-thrust-generating plank of muscle and bone. The tail is also equipped with two rows of special turbulence-reducing little fins, and in order to reach its top speed of around 50 km/hour (needed to catch those speedy herrings), it even tucks its pectoral fins into special grooves on the side of its body.

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The somewhat smaller yellowfin tuna

I have to confess, the tuna is one of my favourites. No fish embodies the sacred philosophy of “just keep swimming” more enthusiastically. Plus, it’s capable of leaping several metres out of the water just to catch a little flying fish. That’s commitment.

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