Fair warning: if you’re a seafood lover who regularly purchases fish from the store or goes out for sushi, proceed with caution. There are some scientific results below that are, at best, upsetting.
At worst? You might vomit in your mouth.
It all began when biology professor Dr. Jennifer McDonald was looking for a way to bring a little excitement to her senior molecular biology course. So she sent them to sushi restaurants and grocery stores and told them to bring samples of their fish back to the lab so they could extract the DNA and determine whether the DNA matched the label.
Image Credit: Twitter
They tested 13 samples and 9 had good enough DNA sequences to determine their species.
So on Friday my Molecular Bio students did a lab about fish fraud. Their Super Important Homework Assignment (TM) was to go out for sushi and take a small sample home in a ziploc bag (EAT THE REST. Wasting food is uncool). Label the supposed fish, put it in the freezer.
— Dr. Jen M (@AwesomeBiota) April 1, 2019
Bring it into the lab next time on campus, put it in our "class freezer" on the bottom shelf.
On Friday, we took those samples, minced them so small it would make world-class chefs shed tears of envy, and extracted the DNA from the fish. Amplified the CO1 gene using PCR.
— Dr. Jen M (@AwesomeBiota) April 1, 2019
Of those 9? Only 2 were labeled correctly.
Yeah. And that’s not the worst part.
Notoriously, students are pretty bad at PCR. Then again, EVERYONE is pretty bad at PCR. It's the kind of thing that you have to practice a lot, it's hard to get a whole class to practice a lot (resources and time and all that), so we use "instructor samples" downstream.
— Dr. Jen M (@AwesomeBiota) April 1, 2019
But this time? HOLY BANANAS THEY ALL GOT RESULTS. I ran the gels today for them & posted results on our course website. Kids, I'm so excited for what these sequences will reveal. The results were *so good*. Better than I've seen in a very long time even considering my own results
— Dr. Jen M (@AwesomeBiota) April 1, 2019
Thursday I'll send them for sequencing and we'll collectively cross our fingers to see what we get. Here's the gel images in case you're curious. Keep in mind this is the…3rd PCR most of these students have set up, and some wells are negative controls. pic.twitter.com/nhVQHtwgrP
— Dr. Jen M (@AwesomeBiota) April 1, 2019
It’s been well documented over the past decade that fish mislabelling is prolific all over the global supply chain – it’s also illegal and results in fines (when detected). According to McDonald, about 50% of fish is believed to be labelled incorrectly (whether intentionally or not), with some species like red snapper and white tuna more likely to be mislabelled than others.
Josue sequenced some red snapper. I put money on that being tilapia and…I was right. Someone owes me $5.
His lab partner, Juanni, sequenced Atlantic Salmon. Comes back as Rainbow trout. Unsurprising. Not the same species AT ALL, but unsurprising.— Dr. Jen M (@AwesomeBiota) April 5, 2019
Not only is it unethical to sell people fish that is not the fish they’re expecting, it can also result in health issues (a common substitute for white tuna is escolar, which can cause gastrointestinal distress) and/or allergic reactions (shellfish is one of the more common – and more deadly – food allergies).
David and Nicolas both sequenced what they thought was Steelhead trout (aka Rainbow trout). David's was smoked, Nic's not.
Nic's was rainbow trout.
David's was coho salmon.
— Dr. Jen M (@AwesomeBiota) April 5, 2019
Moe sequenced one of the two samples (from different restaurants) labelled "white tuna". Often another name for albacore tuna.
It was yellowfin tuna. (NOT the same species!! A trade upwards)— Dr. Jen M (@AwesomeBiota) April 5, 2019
So Dr. McDonald wasn’t shocked at the findings.
Reena sequenced what was labelled (on the box I bought at the grocery store, no less) Icelandic Cod (MSC-certified).
It was. Thank God.Sydney sequenced what was labelled (again, ON THE BOX purchased at the grocery store) Pacific Cod.
It was Atlantic Cod. (CRINGEEEE!!!!!!)— Dr. Jen M (@AwesomeBiota) April 5, 2019
Jade sequenced what the sushi restaurant (who shall remain nameless…it's probably not their fault) called red tuna.
IT WAS TILAPIA!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
— Dr. Jen M (@AwesomeBiota) April 5, 2019
Evalyne sequenced the other sample of "white tuna". That was the one that I brought in, that I theoretically would have eaten if I actually liked and ate "white tuna" (I think it's gross).
It was escolar.THIS IS DANGEROUS. Can cause extreme gastrointestinal distress.
— Dr. Jen M (@AwesomeBiota) April 5, 2019
At least, not until this happened.
Last but not least of successful sample runs, we had one that makes my skin crawl. It was a sequence that came back with a bunch of "unknown bases" (a bit of cleaning up will help immensely) but I worked with what I had and ran it through the database. Was *supposed* to be Salmon
— Dr. Jen M (@AwesomeBiota) April 5, 2019
This salmon was not from a restaurant, but was instead purchased from the seafood department of a local grocery store. Again, to remain nameless. This was purchased from a counter, someone reaches in and grabs the fish, puts it in a bag, sticks a sticker on it, pay by the pound.
— Dr. Jen M (@AwesomeBiota) April 5, 2019
Of a gene approximately 650 base pairs long, I was hoping to get a workable sequence of at least 500 base pairs. This one only had 200 clean pairs before I go through the file to improve the sequence generated. So short compared to expected of "working material".
Ready?
— Dr. Jen M (@AwesomeBiota) April 5, 2019
Body louse.
I think I might vomit in my mouth a little.
I hope this is a mistake. HOPE TO ANY GOD FROM ANY RELIGION that this is a mistake.I hope that this somehow becomes a fish sequence when I clean it up a bit. BUT BODY LOUSE.
— Dr. Jen M (@AwesomeBiota) April 5, 2019
Yeah.
This wasn't a piece of garbage from a market. This was from a "salmon fillet" that someone paid good money for, cut some off before they cooked it, put it in saran wrap & brought it in.
BODY LOUSE.
Think about how much there must be in that sample to override fish DNA!
— Dr. Jen M (@AwesomeBiota) April 5, 2019
Dr. McDonald doesn’t plan to stop eating fish or sushi, and she doesn’t think you should, either – just make sure to go to restaurants where you feel confident in their fish suppliers and ask questions when something doesn’t look, feel, or taste right.
Anyway, I don't know if any of my students are nearly as enthralled as I am about the results of this experiment. I'M THRILLED.
16 students, 13 decent bands on the gel.
Of those, we had 9 with pretty decent sequences. THAT'S NOT BAD.
Of those 9, TWO WERE LABELLED CORRECTLY.— Dr. Jen M (@AwesomeBiota) April 5, 2019
So if you "are what you eat" and you like seafood? You have no idea what you are because nothing is labelled properly. If you want to know what you're eating? Make sure it's from a certified sustainable fishery. They know what they're fishing, and know what they're doing.
— Dr. Jen M (@AwesomeBiota) April 5, 2019
Which might be easier said than done, although the fact that sushi is so delicious should help buck you up.
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