Tuna are fish, and they are wild animals. But to many people, they are simply understood as food. It can be a bit confusing when the short hand of ‘tuna’ is used, as it covers a whole family of species, from the relatively-tiddly and widespread skipjack, right up to the majestic but beleaguered bluefins.
So I've pulled together a quick guide to the tuna species you’re likely to encounter in New Zealand.
This is not intended to encourage you to eat them, you understand, just raise awareness of what it is that is being served up, and what issues you need to think about.
There are about 15 species of tuna recognised worldwide, but in New Zealand, you are likely to only encounter a few of those.
Here’s a quick guide to the species you might encounter:
SKIPJACK (Katsuwonas pelamis)
Relatively small, and the most abundant and widely fished of tuna species. The fish can be up to a metre in length, but is rarely recognisable when served up – as skipjack makes up most of what we eat as canned tuna. Tuna chunks and flakes in brine, or oil – if it’s on a sandwich, baked potato, or pizza, it’s most likely to be skipjack.
This is a pretty abundant species, but there are still issues around how it is fished. Mostly this is because the methods cause damage to other species – which end up as bycatch. Most skipjack is caught using large purse-seine nets, and when these are set around Fish Aggregating Devices (so called FADs, floating structures that lure in tuna and other ocean life) they result in huge amounts of bycatch – of other fish, as well as sharks, rays and even turtles and occasionally whales or dolphins. Using FADs has been shown to increase the amount of bycatch tenfold.
The famous ‘dolphin friendly’ logo on tuna does tell you that it’s not caught in a way that deliberately catches or sets nets around dolphins, but it doesn’t act as a guarantee that other wildlife has not been collateral damage.
Sadly many of the species caught and killed as bycatch are endangered – including several species of open ocean sharks, and sea turtles. And when you factor in the scale of the fishing operation to fill those little cans, that adds up to a whole lot of collateral carnage, including tens of millions of sharks every year.
Luckily – there are better, cleaner, ways to catch skipjack. Look out for pole-and-line caught skipjack, or some that has been caught without using FADs
TOP TIP – only choose pole & line or FAD-free caught skipjack.
YELLOWFIN (Thunnus albacares)
Yellowfin are widespread and magnificently streamlined fish. And, yes, they have yellow fins, including characteristically sickle-shaped elongated ‘go faster’ ones. They are found around the world, but mostly confined to tropical waters. They can grow to over 2 metres in length.
Yellowfin tuna can also be found canned in New Zealand, a fact that has raised the ire of recreational fishers and environmentalists alike. However, yellowfin is probably most recognisable as fresh ‘tuna steaks’ available on the fish counter and in supermarkets, as sashimi or in sushi.
Like skipjack, yellowfin are caught with purse seines, and when FADs are used the vast majority are baby yellowfin that never get a chance to breed. Another method of catching them is using longlines, lines of baited hooks that can be many, many kilometres long. This method of fishing can be very indiscriminate and responsible for lots of bycatch – sharks, swordfish, turtles, and seabirds can all fall victim to the baited hooks.
There are ways to make longlining better, which some suppliers are now insisting on, but the safest way to know that your yellowfin hasn’t come at the cost of lots of other animals’ lives, is to go for pole & line caught.
However, there are now real concerns that populations of yellowfin have been overfished, and in many places are still declining. Recreational catches in New Zealand have plummeted, and even led to the renaming of a tuna tournament as tuna were simply no longer being caught
TOP TIP – only choose pole & line caught yellowfin, and eat it sparingly.
ALBACORE (Thunnus alalunga)
Albacore is a cooler water tuna, it’s caught in New Zealand waters and many of our neighbouring Pacific Islands have important fisheries for South Pacific albacore. They have an unusually long pectoral fin, and are sometimes referred to as ‘white’ tuna, because of its pale flesh.
Albacore tuna can be found in New Zealand in various forms; canned, smoked and fresh. It is caught by both longline and troll fishing, and the New Zealand troll fishery has been, certified by the Marine Stewardship Council.
Globally, most populations of albacore have been overfished – the only relatively healthy stocks are in the Pacific. However, even in our South Pacific waters albacore is getting into trouble, with too many vessels chasing dwindling stocks, and many local Pacific fleets struggling to make ends meet.
TOP TIP – choose MSC certified pole & line or 'trolled' albacore, from the Pacific.
BIGEYE (Thunnus obesus)
With a scientific name that labels it as ‘fat tuna’, this is a big, robust fish, found in tropical waters and growing over 2 metres in length. Sadly bigeye tuna are in trouble, with many populations plummeting in recent years due to overfishing. It’s caught in similar ways to the similarly-sized yellowfin, and whilst you might encounter it served up as tuna steaks, it’s much more likely you would only find it served as sushi or sashimi.
TOP TIP – AVOID BIGEYE
BLUEFIN (Thunnus maccoyii, Thunnus orientalis & Thunnus thynnus)
There are three species of bluefin tuna: Southern, Pacific and Atlantic, and they are spectacular fish. Growing to over 3 metres, and up to a whopping 450kg, they are warm-blooded top predators that can accelerate faster than a sports car, and are also able to tolerate cold water.
However in recent years bluefin tuna has been severely overfished. Atlantic and southern bluefin are already classified as endangered and critically endangered, and Pacific bluefin populations are at only 4% of historic levels. Traditional methods of catching them in traps and on lines have given way to large purse-seine catches targeting them as they come together to spawn. The fashion for sushi has driven this demand, and as they get ever scarcer, and ever more expensive, there are real concerns for the future of all three bluefin species.
In New Zealand bluefin tuna is rarely seen on restaurant menus (as you’d hope for a species that shares critically endangered status with the likes of our beloved kakapo and Maui’s dolphin) but the dire state of the southern bluefin population hasn’t stopped the New Zealand government from repeatedly increasing the local fishing quota.
TOP TIP – AVOID BLUEFIN