Is our appetite for tuna threatening the species’ future? We look at how tuna are fished, issues of sustainability and consumer awareness.
6 Nov 2014 - 4:32 PM  UPDATED 10 Nov 2014 - 12:32 PM

Tasty and easy to catch, tuna is one of the most popular seafood choices around the world.

Since it was first canned at the beginning of the 20th century, tuna has been a convenient way to consume healthy protein.

But as it's grown in popularity, it's also become the poster-fish for questions of sustainability.

Could we be hunting these ocean predators to extinction?

This is one of the issues explored in the new SBS documentary series "What's the Catch?"

Skipjack, yellowfin, bigeye, albacore and bluefin are the species of tuna that humans consume regularly.

Wild fisheries hunt for these tuna throughout the world's oceans - bringing in major commercial catches.

Current sustainability concerns are focused on bluefin tuna, made up of three species in the Southern and Northern Pacific Oceans, as well as the Atlantic Ocean.

Bluefins are large, slow-growing fish that take at least a decade to reach maturity.

In a narrow sense, sustainability refers to whether a certain fish can be caught at the same rate, year after year, without threatening the species by overfishing.

Independent marine biologist and author of Fishes of the Open Ocean, Dr Julian Pepperell, says slow-maturing fish like bluefin tuna are more vulnerable to the risk of being overfished.

This is because they can't reproduce quickly enough while their ranks are being thinned by fishermen.

The fish stocks that tend to be resilient to fishing, and the fish stocks that are good to fish, if you want a renewable, sustainable resource, are the species that grow quickly and mature at an early age.

However, this doesn't mean that a species will go extinct due to fishing.

As Dr Pepperell explains, that would be hard to achieve.

There's no example of any fishery in the whole world that's been fished to extinction. Before that happens, the economics of the fishery would cause it to slow down and stop, basically, and that's the history of overfished fisheries. The idea of extinction is a little bit hyperbolic, really.

Greenpeace Australia Pacific oceans campaigner Nathaniel Pelle explains why tuna is such a focus for the marine conservation group.

If we can get tuna fisheries and tuna trade managed sustainably, then we hope we can then translate that to other fisheries that aren't doing so well. And tuna are historically in a lot of trouble.

According to the International Seafood Sustainability Foundation, in 2012 the five commonly fished tuna species comprised a global catch of 4.6 million tonnes.

Australians consume nearly 40 thousand tonnes of canned tuna a year, and almost all of it comes from the Western and Central Pacific Ocean.

Dr Pepperell argues that the species used in these cans is in no great danger.

Canned tuna is mostly skipjack tuna, which is a small species of striped tuna that is one of these species that has a short lifespan, matures early, grows quickly, it is a good species to fish. Now, if that's fished cleanly, it is a sustainable fishery.

Sustainability also means the environmental impact of the fishing method used, as well as other factors such as fair employment standards.

Dr Pepperell says some fishing methods are more popular than others.

The main method that is used for catching tuna for canning is what they call purse seine It's a very large net, the size of a football field, that is run around a school of tuna; these days the school of tuna will be attracted to what they call floating aggregation devices, which are basically just a buoy on a chain. Tuna, for whatever reason, love hanging around these FADs, so big fishing companies put lots of these aggregating devices around the South-Western Pacific.

A FAD will attract more than one type of marine life as other unwanted species are caught along with the tuna.

They're known as bycatch and can include large numbers of endangered oceanic sharks, as well as sea turtles and dolphins.

As Nathaniel Pelle explains, Greenpeace believes the most responsible method to fish is the old-fashioned way.

We've been heavily promoting pole and line tuna as the best option; that's tuna caught in a really traditional fashion, with really good employment outcomes. It's basically fishermen standing on the back of the boat, each with a pole and a line of their own, catching tuna and reeling it into the boat.

Large companies in the Pacific region often prefer using high-yielding methods like purse seine with FADs.

This means higher amounts of bycatch, but also fewer jobs for fishermen from developing countries.

Tuna is a highly migratory fish, not confined to the waters of one particular country.

Fisheries social scientist at the University of Technology Sydney, Dr Kate Barclay says this makes enforcing sustainability practices difficult.

Our main ways of governing natural resources runs through governments, national governments mostly, and then they filter down to state and more local levels. Whereas tuna are an international resource, and the move around, so they cannot be effectively governed by individual governments.

Stepping into this space are Regional Fisheries Management Organisations.

These bodies comprise member countries of a specific area - setting catch limits and monitoring health of the species in their waters.

Cooperation within these bodies remains a challenge, because member countries don't always agree upon conservation measures, and agreement isn't enforceable.

Distant-water fishing, where countries such as Japan and Korea have fishing fleets active far outside their territorial waters, further complicate efforts to control practices.

Greenpeace's Nathaniel Pelle says that distant-water fishing can take resources away from developing Pacific Island countries looking to benefit from the rich marine life in their waters.

He says Australia has its role to play in pressing our neighbours to improve their standards.

We are the biggest economy by far in the region. And we would hope that our industry and our government would support stronger diplomatic measures to reduce overfishing and destructive fishing by the distant-water fleets.

Consumers and conservation groups can influence matters as well.

Since 2008 Greenpeace have published a canned tuna guide for shoppers, grading brands of tuna on their fishing methods, labelling, species choice and sustainability practices.

Mr Pelle says food companies often start with establishing what are the ground rules on the tuna they source.

The first thing is that they must have a sustainability policy to start with. And when we first made the ranking in 2008 in Australia, a lot of tuna companies didn't even have a set of guidelines for how they source their tuna. So that's the first step - making sure there is a policy in place that dictates what tuna they can and can't buy to sell to their customers.

UTS' Dr Kate Barclay says guides like these are important because companies care about their reputation.

Their buyers may say, "we want this label, or we want to be able to be sure that what we're putting on our shelves is not going to cause us any reputation problems if it's been illegally fished or unsustainably fished. So you make sure that what you supply us meets some kind of criteria for sustainability." This really is affecting what's going on down the supply chain.

She says guides help consumers navigate the complexities of the sustainability debate.

Sustainability issues for anything are very complex, working out exactly what mode of production is going to be the most sustainable has so many factors involved. Normal consumers don't have time to gather all that information.

For fans of tuna, the good news is that there's no need to stop eating it altogether.

Campaigners argue a little mindfulness on your choice of tuna goes a long way.

SBS' new three part series "What's the Catch?" airs Thursdays at 8.30PM from 30th October on SBSONE.