Researchers have found shark meat in more than a dozen brands of pet food through DNA barcoding, a process that identifies species using short strands of DNA and compares them to sequences on file.
Marine conservationists Ben Wainwright and Ian French, who co-authored a new report in the journal Frontiers in Marine Science, examined 45 different pet-food products from 16 brands commonly available in Singapore. Out of more than 140 samples, the researchers at Yale-NUS University in Singapore found roughly a third contained shark DNA.
The most commonly identified was the blue shark, followed by the silky shark and the whitetip reef shark.
"None of the products purchased listed shark as an ingredient, using only generic catch-all terms such as 'fish,' 'ocean fish,' 'white bait' or 'white fish' to describe their contents," the authors wrote in a release.
Because of their slow reproductive rates and unregulated fishing, both whitetips and silky sharks are listed as "vulnerable" by the International Union for Conservation of Nature.
Wainwright and French say the decimation of shark populations from overfishing -- with declines of some species surpassing 70% -- is "indicative of the current lack of regard in which we hold our oceans."
Shark products find their way into a surprising number of household products, often disguised under vague ingredient names. For instance, squalene, the oil from a shark's liver, is used in some cosmetics -- including lipstick, moisturizer and mascara.
The issue isn't limited to Singapore: As a doctoral student at New York's Stony Brook University in 2019, marine biologist Diego Cardeñosa used DNA barcoding and found scalloped hammerhead and shortfin mako shark meat in canned wet food, dry food and treats he bought online and in supermarkets. (Both makos and hammerheads are classified as endangered by the IUCN.)
It's unlikely sharks are being killed specifically to wind up in cat food. But even if they were, fishing for many shark species is perfectly legal in many parts of the world, including the US.
It's a question of transparency in ingredient labels, French and Wainwright say. Consumers have a right to know exactly what's in their pet chow.
"The majority of pet owners are likely lovers of nature," they wrote. "We think most would be alarmed to discover that they could be unknowingly contributing to the overfishing of shark populations."