Tuna is one of the most commonly consumed fish globally, eaten mainly as canned meat, tuna steaks or in sushi. The global tuna business is worth over £3 billion annually, with millions of people relying on this industry for their livelihood, but some tuna species are becoming highly endangered because of the increasing demand for fresh fish. But for many, it’s unclear whether canned tuna fits into the endangered category or not.
There are seven tuna species that are caught and consumed: Albacore, Bigeye, Skipjack, Yellowfin, and three species of Bluefin: Northern Bluefin, Pacific Bluefin, and Southern Bluefin. The type of tuna we hear mentioned most in the discussions and debates about tuna sustainability are the Bluefins. These fetch an extremely high price on the international fresh fish market, which makes this type of tuna unlikely to be used for canning. Populations of Bluefins are also heavily exploited because of their high value, and have seen massive declines in population in recent years. More information can be seen in our article, ‘Hook, lies and sushi’.
With Bluefins out of the equation, a number of other species are used in canning. But even though these types have less impacted populations, there are a number of issues centering on where and how these fish are caught.
Methods of catching tuna
There are three main methods of catching tuna, each coming with a set of environmental impacts:
- Pole-and-line: Also known as trolling. This simple method is considered the least destructive way to catch tuna, and involves a baited fishing line on a pole, and has very low by-catch rates (caught unintentionally). Unfortunately, a very small percentage of tuna are caught this way.
- Long-line: This is done by releasing long fishing lines, strung with shorter lines and baited hooks attached. This practice is not selective and can result in large amounts of by-catch. Seabirds are particularly vulnerable to this method.
- Purse seine: Involves a wide net, which encircles an area where fish are located. This method results in significant by-catch of other fish, turtles and marine mammals.
Top tip: If you’d like a more comprehensive list of tuna fisheries, have a look at this fact sheet from the Monterey Bay Aquarium Seafood Watch program.
Difficulty rating: Simple
Cost rating: Free
The tuna industry has adopted measures to try and limit the amount of by-catch, and the impacts on dolphins and other marine mammals, through dolphin-friendly certification. This labelling can, however, be confusing, or even deceptive. The matter is further complicated because:
- There is more than one certification standard, and all claim that no dolphins were harmed in catching their tuna.
- Some of the methods used for catching tuna, labelled “dolphin safe”, may actually be causing harm to dolphins.
- Dolphins aren’t the only by-catch in tuna fishing.
Top tip: Look out for products that are dolphin-safe or dolphin-friendly, as these use tuna caught using the poll-and-line method.
Difficulty rating: Simple
Cost rating: Certified products may cost a little more
All this certification labelling can become rather confusing. In the UK, check for the Marine Stewardship Council [MSC] certification to make sure that your product is sustainable. In the US, the American Albacore Fishing Association is a non-profit organisation representing commercial pole and troll vessels, and verifies eco-friendly practices onboard tuna vessels.
What’s in the can?
Labelling on tuna products is not a reliable indicator of the species used or of their origin, as canned tuna is often a by-product of more than one country. Unless these details are specified on the can, it is difficult to judge how sustainable a product is.
There are a number of health issues related to eating tuna, even the types that end up in cans. Recent studies of canned tuna have revealed that more than half of said cans contained mercury levels above what is considered safe by the EPA. It is estimated that 75% of mercury contamination in humans occurs as the result of eating fish. Young children, women, pregnant women and nursing mothers are most vulnerable to mercury effect, and should strictly adopt the guides of fish consumption.
The good news (if one can call it that) is that tuna steak contains higher mercury than canned tuna. This is because the product comes from bigger types of tuna: Bluefin, Bigeye and Yellowfin, which accumulate higher levels of mercury contamination than the smaller type of tuna, like Skipjack.
Top tip: Opt for canned tuna made from skipjack, as it appears to be less damaging to the environment and your health.
Difficulty rating: Simple – may not be able to find product details on can
Cost rating: No cost difference between products – may cost a little more
Are canned goods all that good?
Canned tuna is a quick, easy meal option, and will probably be on the menu for a long time to come. As responsible seafood consumers, we ought to consider the environmental facts before picking up a can.