The Chilean seabass is no stranger to being mislabelled. It bears little relation to the various fish that are also known as basses, and it’s more properly referred to as the Patagonian toothfish (a name that is presumably more difficult to market). But the confusion doesn’t end there. While the toothfish is the target for illegal and unsustainable fishing operations, the Marine Stewardship Council (MSC) has certified one fishery as being sustainable. It’s found around the island of South Georgia near the tip of South America.

But some products marked as certified toothfish don’t come from this fishery. Some aren’t even toothfish at all.

Peter Marko from Clemson University, South Carolina bought 36 samples of MSC-certified toothfish from 10 American supermarkets, and analysed the DNA within their mitochondria – small battery-like structures in their cells with their own genes. He compared this DNA to fish from the protected South Georgia stock. He found that 14 percent of them came from unsustainable fisheries in other parts of the world. Eight percent of them aren’t even the right species. When people eat “certified Chilean seabass”, there’s a one in twelve chance that they’re eating something like tuna, greenling or mackerel instead.

Marko’s study will add controversy to the fishing of an already controversial fish. It’s a slow-growing, long-lived Antarctic species that is reeling from overfishing. In the 1990s, a boom of demand from American diners slashed the Southern Ocean’s toothfish stock by around 60 percent. Today, illegal fishing is still rampant. Several high-profile arrests and lengthy chases have cornered ships carrying many tonnes of toothfish, but poachers continue to find ways of outfoxing the authorities.

Partly, the responsibility for the toothfish’s decline falls upon the diners who crave its flesh. Their appetites drive the fish’s high market value, giving it yet another name: “white gold”. Various organisations, from Monterey Bay Aquarium to Greenpeace, have warned people to avoid eating the toothfish, and the MSC’s certification scheme has gone some way towards labelling the one stock that might be considered sustainable. Now, even the integrity of that scheme is in doubt.

Marko was surprised. “We had no reason to believe that there was any product mislabelling,” he says. “Given the controversies surrounding the sale of Chilean sea bass from any source, the high price of MSC-certified Chilean sea bass, and the extensive marketing of this particular product to environmentally-conscious consumers, I was expecting no substitutions of any kind.”

Some might argue that toothfish might have migrated to South Georgia from other places but Marko thinks that this is unlikely. The South Georgia stock is very genetically distinct and probably isolated from toothfish anywhere else in the world. Even if there had been some recent migrations, the species has such large gaps between generations that it’s unlikely any newcomers would have greatly affected the frequency of genetic markers in the South Georgia contingent.

Consumers are now in a tricky position. Marko says that they can ask about the origins of the fish they’re planning to buy, or even ask to see the paperwork that accompanied a shipment (MSC-certified toothfish had an extensive paper trail precisely for this purpose). “However, for consumers that do not want to inadvertently support any uncertified Chilean sea bass fisheries, the best thing to do is not buy these fish until more studies of the supply chain integrity can be conducted by independent groups,” says Marko. The risk is too high.

This problem is not confined to the Patagonian toothfish, and genetic studies have started to show how widespread dodgy labels can be. In 2004, Marko showed that three quarters of fish sold in the US as “red snapper” are nothing of the sort. Other researchers have found that over half of tuna samples from US sushi restaurants came from unrelated species or the endangered southern bluefin tuna. Altogether, throughout North American and Europe, an estimated 20 to 25 percent of seafood products are fraudulently labelled.

This isn’t just an issue of conscientious people getting duped. Consumers vote with their purchases, and Marko points out that by buying “sustainable” fish that isn’t, we create misplaced demand for uncertified fisheries. And that undermines one of the basic principles of certification.

Reference: Marko, Nance & Guynn. 2011. Genetic detection of mislabeled fish from a certified sustainable fishery. Current Biology citation tbc.

Image from mccunn934

More on fishing:

• Satellite pictures reveal “landscape of fear” in Great Barrier Reef
• Overfishing gives toxic seaweeds an edge in their competition with corals
• Vegetarian piranhas are the Amazon’s champion gardeners
• Fishing bans protect coral reefs from devastating predatory starfish

August 22nd, 2011 by Ed Yong in Environment, Fishing, Genetics | 5 comments | RSS feed | Trackback >