Mindblowing video shows why tinned tuna found in supermarkets is so cheap

There is one fish that Britons love to whack on their jacket potatoes, sarnies, and pasta bakes, and that’s tuna.

It’s an incredibly versatile fish - whack a bit of mayo in it, and you’ve got tuna mayonnaise, or go without if that’s not your cup of tea.

One can of tuna is pretty cheap, costing anywhere from 45 to 55p in some supermarkets, so how come it’s not the same when you go to a place like a sushi restaurant?

Here in the UK, tuna sushi, especially the good stuff, could see you spend upwards of £30 in some cases, according to FineFoodSpecialist.co.uk

In Japan, where tuna sushi is fractionally cheaper, the fish still commands a substantial price. Just this year, sushi restauranteurs spent £1 million on a ‘motorbike-sized’ tuna fish, the BBC reports.

But while canned tuna and expensive tuna are both derived from tuna fish, there’s a reason why the price is so different between the two, and a video uploaded to YouTube delves a bit further into why.

Why is canned tuna so cheap?

Everyone's got a couple of cans of tuna in their kitchen (Getty stock images)

You might have seen a tuna steak while at your local sushi joint, which looks impeccable, almost red and importantly, raw.

This isn’t what’s canned for your supermarket run - and that's because while they are both tuna, it's because they come from different species of tuna fish.

In fact, canned tuna tends to come from smaller breeds, such as skipjack and albacore tuna, which are abundant in the sea, making it an accessible and cheaper fish to farm.

According to the video, it also only takes one to two years for the fish to mature so there’s a very short window to wait to harvest the meat per generation.

Where the expensive tuna actually goes

This year wasn't the only instance of tuna being sold for an incredibly high price, as in 2013, a 489-pound tuna sold for $1.8 million, and it certainly wasn’t the same quality as the fish you can.

Skipjack tuna is what's more commonly found in supermarket tuna (Eko Prasetyo/Getty images)

Expensive tuna usually comes from the hard-to-find Gold of The Sea, bluefin tuna fish.

While the skipjack takes up to two years to mature, bluefin can take anywhere from eight to ten years- which is a long time to wait to harvest a fish.

All in all, the bigger fish is a delicacy that’s far too scarce to eat every day. With so much demand, comes an entirely different process to turn it into high-end sushi.

According to an interview from Business Insider with Boston sushi chef, Derek Wilcox, in 2018, when bluefin is processed in the US, for example, it’ll go from the fisherman to the distributor and straight to the restaurant.

But when it comes from Japan (which is supposed to be the best fish choice), it goes from the fisherman to a collective or cooperative party, to the government auction, to a middle wholesaler, to a final wholesaler, and then to the restaurant.

Bluefin tuna is highly prized (Enrico Spanu/REDA/Universal Images Group via Getty Images)

Wilcox says that Japanese handling is done with more care, and is more precise in its cuts.

Because of the high demand, however, there's also the risk of overfishing, as World Wildlife state that bluefin tuna makes up 1 per cent of a daily catch.

They also say that the bluefin tuna population has severely declined as a result of overfishing, commercially and illegally, as adults are being caught and killed faster than they can breed.

What issues can arise from eating canned tuna?

Tinned tuna is a great source of protein and minerals, but Bloom, a marine conservation organisation based in France, released a report about levels of mercury in tinned tuna - and it wasn't looking good.

Fish naturally contains mercury as it’s in their natural environments, and tuna, which is a predatory fish, contains more than something like cod as it eats other fish and absorbs their mercury content too.

Older and bigger fish will also contain more as they stay longer in the environment. That’s why there is a maximum level for mercury in tuna and species of 1.0 mg/kg.

It was speculated that canned tuna contained ‘toxic levels’ of mercury, however, the UK government explained their process to ensure that all tuna contains below toxic levels.

Ultimately, businesses need to ensure they are keeping their fish below the level, and if any fish is found to contain more, it must be pulled from sale.

This is because mercury can be dangerous in certain doses, particularly to children and pregnant women.

The NHS suggests only eating 4 cans of tuna a week or no more than 2 tuna steaks a week.

For children, too much mercury can cause learning disabilities and developmental delays.

For infants and foetuses, high doses can lead to things like cerebral palsy, deafness, and blindness, and for adults, it can cause fertility issues, blood pressure problems, memory loss, tremors, vision loss and numbness of extremities.

All in all, as long as you’re not gorging on your cans of tuna, you should be alright.