Few consumers picking up a tin or a pouch of pet food containing fish will pause to consider the origin of the contents, or what species they were made from.
But research suggests that we should think about what goes into the heavily processed food we feed our cat or dog.
When researchers in Singapore analysed 144 samples of pet food on sale in the country, they found that 31 per cent contained shark DNA – some from species listed as vulnerable.
Most common was the blue shark (Prionace glauca), then the silky shark (Carcharhinus falciformis) and the whitetip reef shark (Triaenodon obesus).
“None of the products specifically listed shark as an ingredient, listing only generic terms, such as ‘ocean fish’, ‘white fish’ and ‘white bait’,” the authors of the study, Ian French and Dr Benjamin Wainwright, wrote in Frontiers in Marine Science.
Other research found that about one in three seafood samples is mislabelled, sparking concerns about “seafood fraud” and leading one operator in the sector to describe the fishing industry as dysfunctional.
Among the scientists researching the DNA barcoding of seafood is Prof Stefano Mariani, of Liverpool John Moores University in the UK. The Singapore findings come as no surprise to him.
“It’s just something that unfortunately happens in many different forms,” he says.
“When you have pet food, generally it’s in a tin or sachet. It’s like a pulp or little pellets. It’s very indistinguishable. It has a lot of ingredients and it’s very heavily processed.”
Determining from which species ingredients were sourced is not easy. After a few steps in complex supply chains, “information is lost”. Single harmonised system (HS) codes, using a standardised international system to label traded goods, may cover hundreds of fish species.
Often problems begin early on. Sharks may be trans-shipped from one fishing vessel to the next, says Francis Neat, professor of sustainable fisheries management, ocean biodiversity and marine spatial planning at the World Maritime University in Sweden.
“At the point the product enters into the processing point and it starts to get mixed up with other ingredients, it becomes probably extremely difficult to have the right checks and balances as to what is there,” he says.
“[This] is why these DNA methods are the first attempt to understand that or get a handle on the extent to which this is going on.”
When it comes to the pet food analysed in the new study, the authors suggest there are conservation concerns about the top three shark species they identified.
They say research indicates that the blue shark is “overexploited and should have its catch regulated”, while the International Union for Conservation of Nature lists the silky shark and the whitetip reef shark as “vulnerable”.
Sharks as a whole have suffered badly at the hands of human beings, with populations shrinking 70 per cent over the past half century. According to 2021 research cited in the new study, three quarters of oceanic shark species are at risk of extinction. Fishing is regarded as their biggest threat.
In this context, Prof Neat feels that there is a responsibility on pet food manufacturers to ensure that the ingredients they use are sustainable.
“There are ways to do that,” he says. “There are certified fisheries you could source your products from which provide some certification of the species and origin of that catch and where it comes from.
“There are national or multilateral agreements, such as the EU, which has a catch documentation scheme that to a broad degree assures the species is the species it says on the label.”
DNA testing identifies what species are present in food (whether human food, pet food of aqua-feed given to farmed fish) and can indicate whether a certification scheme is working.
The Marine Stewardship Council (MSC), a non-profit organisation that sets sustainable fishing standards and certifies human and pet food, uses this to validate products sold with its certification.
With the MSC, Prof Neat, who used to be the organisation’s head of strategic research, says there is “very good agreement” – more than 99 percent – between what the species is being sold as and what it actually is, based on its DNA.
Not all sustainable fisheries are certified, Prof Neat says, so there are other options for people trying to ensure that the food that they or their pets eat does not have conservation implications.
Among the commercial companies offering DNA testing is Norwegian-based Orivo, which carried out its own pet food screening and found 60 per cent of the products contained undeclared species.
“These were not endangered species, but species that are priced lower, so we suspect economically motivated fraud,” says Erik Fuglseth, Orivo’s chief technology officer.
Mr Fuglseth says there is increasing concern about transparency among consumers and, as a result, also among retailers, brands and manufacturers, but complex supply chains make vigilance important.
“When raw materials such as fishmeal are transported long distances through multiple middlemen, it can often be challenging to monitor if other sources are mixed by intention into the raw materials, due to supply-demand challenges or to maximise profit,” Mr Fuglseth says.
“We are focused on helping honest and responsible players document that their products contain what they claim.
“Our technology is sensitive enough to detect even small amounts of specific species, and can be used as an efficient way to verify the end of complex value chains, and thereby detect adulteration by endangered species.”
In developing nations it can be particularly hard to have effective surveillance, so the risk is probably greater that the species or origin of fish is not well documented, according to Prof Neat.
“The problem comes when you have the illegal [operators] catching sharks for their fins,” he says. “There’s a big market for shark fins in Asian countries. A lot of that is likely to be illegal or unregulated.”
Catching sharks for their fins, which are regarded as a delicacy, has caused the over-harvesting of many species and even made some critically endangered.
“There’s still a lot of species that are potentially endangered and the trade of which is not really regulated. It’s easy to lose track of what happens to the animals,” Prof Mariani says.
He cautions, however, against seeing pet food as a key driver in the exploitation of threatened sharks species. Instead, he says, the shark ingredients in pet food – perhaps an oil, for example – may be a by-product of catching sharks primarily for their fins.
“It ends up with different suppliers, different people,” he says. “It’s a very complicated trade. The liver is used for oil, the cartilage for materials that give a certain texture. It’s distributed.
“Cat food is not a premium product like blue-fin tuna. It’s the stuff that’s used to make bulk, so the by-product of these catches ends up in pet food. That’s not to say it’s a good thing.”