What fish is on your plate? Maybe not what you think

Turns out that 25 percent of the time, it’s not the fish you thought you had bought. At least that’s what two recent high school grads in New York City discovered after conducting a small study of the Big Apple’s seafood markets and sushi restaurants.

A story by John Schwartz in today’s New York Times described the study. Kate Stoeckle and Louisa Strauss gathered 60 fish samples from four restaurants and 10 grocery stores and had them analyzed with a DNA technique scientists are using to identify fish species. It’s called fish barcoding, because one small section of a fish’s genetic code is unique, so scientists can use them like barcodes at the store. By comparing samples to a library of these unique sections, or fish “barcodes,” you can identify your sample.

I interviewed NOAA senior scientist Bruce B. Collette about fish barcodes back in May. Here’s the radio segment from that interview: Building a global fish-barcode library

The global effort to catalog these fish barcodes is called the Fish Barcode of Life initiative, or Fish-BOL. They’re trying to barcode all 30,000 species of fish in the next few years.

The girls peformed a useful experiment with surprising results. I’m somewhat shocked that 25 percent of the fish were sold under different names. Maybe I’m just naive about the industry. It’s a small sample, of course, in a very big city, so it’s hard to say how prevalent fish fraud may be. But we know that it is happening.

I also didn’t know the public could start sending samples to the Fish-BOL team; I’m trying to find out if this was a one-off thing or if we can all start sending samples, or if we can get fish tested at all at this point.

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Update, August 22 at 8:37PM ET: Paul Hebert, co-chair of the Fish-BOL Initiative, told me via e-mail that his team will test fish samples for interested members of the public, for a $25 fee. The fish sample can be fresh or cooked, although Hebert says he can’t promise a full-length sequence if the sample is cooked. You must send it preserved in ethanol (ethyl alcohol). If you don’t have a vial with ethanol, Hebert’s team will send you one. Keep the fish in your fridge while you wait to receive the vial. You can find contact info on the Fish-BOL Web site. I’ll post more specific contact info as I receive it.

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In any case, I wanted to share more of what Collette told me a few months ago about the scientific uses of fish barcoding, beyond identifying the fish you bought at the store. Here’s what he said:

“Another use that’s very important in fisheries to the National Marine Fisheries Service, is identification of larvae … Larval marine fishes are like caterpillars and moths, they’re very different from the adults and we need a whole other set of characters to identify them. Now, we can take an eyeball from a small larval fish and get the DNA from that and match it, or compare it, with the DNA from adults of all the species known to occur in the area and we can determine what it is. So, we can for the first time, positively identify larval, very small larvae of the commercial species of tunas. This has been very difficult in the past, and almost impossible in some cases, but it can now be done using barcodes.”

Collette also noted that fish barcoding will help with fishery law enforcement, identifying by-catch and protecting endangered species.

“Our fisheries catch lots of species, but the American consumer only is interested in eating certain species, but we have to worry about concentrations of other species that are being caught, too. And we put observers out on many fishing vessels, but it’s difficult for them to document what was collected. But if we give them a whole series of small vials with alcohol and they can just drop a piece of tissue in and then they come back and have it analyzed and say, well, you were catching an endangered species and you shouldn’t do that. So, that kind of enforcement of by-catch, endangered species and forensic identification are all going to be made much simpler once we’ve got the library of DNA codes in a given region.”

One endangered species did turn up in the girls’ experiment — Acadian redfish. So not only are some fish markets committing fraud by selling one fish under the name of another, but they’re also selling illegal fish. I assume endangered species are illegal to sell, at least I’d hope they would be. This practice is wrong; hopefully NOAA can start using fish barcode analysis soon to protect endangered species and seafood consumers.

What do you think of this fish story and the fish barcoding? Post your comments here!