Tuna are awesome. We don’t get to say that enough, so since it’s World Tuna Day, I want to make amends. These fish are majestic ocean wanderers who have earned their place in history. But because tuna are now a a globally-traded commodity, they have become the icons of global overfishing and dodgy fishing methods.
There are 8 recognised species of ‘true’ tuna (Atlantic bluefin, Pacific bluefin, southern bluefin, bigeye, yellowfin, albacore, longtail & blacktail) and a further 8 species in the extended family that are normally called ‘tuna’.
In the Philippines, the most common tunas and billfish include yellowfin, bigeye, skipjack, eastern little tuna, frigate tuna, bullet tuna and some albacore.
Skipjack, the most commonly-eaten tuna is not biologically a proper tuna, it’s more of a distant cousin.
Big tuna are super-predators. They eat fish that eat fish, so they are a few steps up the food chain. That makes them comparable with tigers, or wolves on land. Being high up the food chain has its disadvantages – it also means that the bigger species like bigeye and bluefin also accumulate more toxic chemicals, most notably mercury.
Bluefin tuna are also called ‘red tuna’ because of the colour of their flesh. It’s red because it’s oxygen-rich. These fish are effectively warm-blooded, and regulate their temperatures.
Being warm blooded means that bluefin can live in cooler waters - being big also helps deal with cooler climates. Although there are a lot less of them around these days, bluefin tuna have been found as far north as Norway, and used to be a popular fish for anglers to catch in the North Sea.
Bluefin are fast. They can accelerate quicker than a sports car, which is a force to be reckoned with when a fully-grown bluefin can be 3metres long or more.
The front fins on a tuna 'fold down', tucking into handy grooves and making them more hydronamic - perfect when the tuna feel the need for speed.
The propulsion in a tuna comes from the stiff crescent-shaped tail. All the muscles in the body effectively drive the tail which in turn drives the tuna.
Yellowfin tuna are the ones most likely to be seen doing acrobatics out of the water - perhaps to show off their go-faster long curved (yellow) fins.
Albacore meanwhile are blessed with a fine set of pectoral fins. Perhaps they are heading for an evolutionary leap out of the ocean, after picking up some tips from flying fish.
Albacore are sometimes known as ‘white tuna’ because of their pale flesh. That has also earned them the dubious nickname of ‘Chicken of the sea’.
Yellowfin tuna hang around with dolphins. Whilst it’s hard to tell if either group is a bad influence, this led to a horrific practice of targeting and killing schools of dolphin to catch the yellowfin. This caused international outrage, and led to changes in the fishing techniques and the widely used ‘Dolphin Friendly’ logo that is attached to almost all tuna sold today.
Female tuna are capable of producing up to 30 million eggs. They are mass spawners, which can be a very, er, messy way or procreating, and usually means they are very fickle about getting the water temperature just right before making baby tuna.
Apparently some yellowfin like to breed while they feed, which is even messier, and probably not worth dwelling on…
Bluefin have been fished in the Mediterranean since at least 2000BC, and it is said that their shoals sustained Roman legions. But it has been the impact of the relatively-recent industrialisation of fishing that has plunged Atlantic bluefin to the brink of extinction.
The decline of bluefin has led to crazy demand for prize specimens – in 2013 over £1million ($1.8 million) was spent on a single fish in Japan.
So tuna are undoubtedly awesome. Given half a chance, they should be able to survive in our oceans, but as we already know, we humans are having a pretty huge impact on tuna and their ocean home.
Here are a few ways you can help tuna on World Tuna Day:
1) Don’t eat tuna. Skip the skipjack for a day (at least). They deserve a break.
2) Eat tuna better. If you do eat fish, only choose responsibly-caught tuna, try asking your retailers
3) Support Greenpeace’s oceans campaign. We’re tackling overfishing, destructive fishing and climate change, as well as trying to build support for ocean sanctuaries, and transform tuna markets. But we need your help.
4) Share this, and tell a friend why you think tuna are awesome.
For a quick, illustrated guide to tunas you might frequently encounter, click here.