• Nearly a third of shark meat samples taken from products sold in Europe contained dangerously high methylmercury levels, with all tope shark and almost a quarter of blue shark samples exceeding EU safety limits, a new study finds.
• Much shark meat is mislabeled under names like rock salmon, huss or veau de mer, leaving consumers unaware they’re eating shark and could be ingesting a potent neurotoxin.
• Methylmercury can’t be cooked out, builds up in human tissue and can cause lasting neurological harm. Meanwhile, shark populations are declining, threatening marine ecosystem stability.
• The study’s authors urge stricter labeling laws, tighter food monitoring and consumer education, arguing that eating apex predators is both ecologically and medically unsustainable.

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Shark meat sold across Europe may be serving up more than seafood. Dangerously high levels of methylmercury, toxic to humans, were present in nearly a third of shark meat samples taken from European restaurants, fishmongers and supermarkets, according to a new report by a group of marine conservation NGOs.

The findings suggest that Europeans are routinely consuming shark meat that would fail food safety tests if it were monitored more closely.

All tope shark (Galeorhinus galeus) samples and 22.7% of blue shark (Prionace glauca) samples analyzed exceeded safe levels, some by more than four times the maximum permitted in shark meat for human consumption under EU rules. Average mercury across all samples analyzed was less than a 10th of a milligram per kilogram below the maximum permitted, according to the report.

“We were astonished at how high the contamination levels were in all of the samples,” report co-author and marine biologist Julian Münster of the German campaign group Stop Finning Deutschland, told Mongabay. “We did not expect the average methylmercury contamination to be just below the maximum limit.”

Who eats shark meat, though? You may well ask. The report, published Oct. 15, also raised concerns about misleading shark-meat labeling, citing examples where retailers make up names they consider more appealing to consumers than “shark.” These include rock salmon or huss in English, schillerlocke in German and veau de mer, roussette or saumonette in French, the report said.

“As things stand, people are consuming contaminated fish without even knowing it,” Münster said.

Shark fishing in the North Atlantic Ocean, photographed in 2019. Image courtesy of © Kajsa Sjölander / Greenpeace

Bioaccumulation in an apex predator

Human activity has increased atmospheric mercury by 450% above natural levels, according to the U.N. Environment Programme. Mercury enters aquatic environments through human pollution from industrial emissions and waste incineration. It occurs naturally from volcanic activity and rock weathering.

Once in the water, microbes convert mercury into methylmercury and a process called bioaccumulation begins: Small organisms at the bottom of the food chain consume methylmercury in tiny quantities, then small fish and invertebrates eat them, taking on their combined mercury load. Larger fish, and eventually sharks, eat these mercury-laced prey fish. Methylmercury remains in fish for around two years, according to previous research. Meanwhile, the more mercury-containing prey a fish eats, the more mercury builds up in its muscle tissues, which may end up on your plate.

Big predators, like sharks, are known to accumulate especially high doses over their long lifespans, with older and larger sharks likely carrying the heaviest loads.

Methylmercury can’t be removed by cooking or freezing, and it accumulates in the human body over time, just as in fish. At high enough doses, it can cause neurological issues, such as uncontrollable shaking, memory loss, blindness and seizures. The effects are often permanent. Fetuses and young children are especially at risk.

Consumption of shark meat also raises concerns for the sharks themselves. As apex predators, sharks are “essential” to healthy marine ecosystems, Münster said. Yet many species are in decline because their low birth rates mean they often cannot sustain the high fishing levels they are subject to.

Conservationists have long sounded the alarm about the trade in shark fins, driven largely by demand in Asia, while the market for shark meat has largely escaped public attention. Yet meat earned almost twice the revenue of fins between 2012 and 2019, at $2.6 billion, WWF research found. European imports and exports account for 22% of the global shark meat trade, it showed, with Spain the biggest exporter.

A tope shark (Galeorhinus galeus), also known as a soupfin shark or school shark, photographed in Port Elizabeth, South Africa. Image courtesy of Andy Murch / sharksandrays.com

Inside the report

The report examined 51 shark meat samples from France, Germany, Spain, Switzerland and the U.K., 44 from blue sharks and seven from tope sharks. The samples were deep-frozen and analyzed for methylmercury concentration in an International Organization for Standardization-certified lab.

The researchers chose blue shark because it is the most common shark species on the European market. Forty of the samples were traceable to North and East Atlantic fisheries, with almost a quarter showing mercury levels exceeding the EU’s permitted maximum of 1 mg of mercury per kg of meat.

All of the tope shark samples exceeded the EU’s permitted maximum, with up to 3 mg of methylmercury per kg. The report’s authors note that the tope sample size of seven specimens, all from the Spanish market, was limited.

The report is not peer-reviewed, but was proofread by Bethanie Carney Almroth, a professor of ecotoxicology at the University of Gothenburg. The authors, from German research and conservation organization Elasmocean, Swiss environmental philanthropy the Gallifrey Foundation, as well as Stop Finning Deutschland, decided against submitting their work to a scientific journal at this stage to inform the public quickly, Münster said.

This report is important for shark populations, which are declining, as well as for human health, Neil Hammershlag, a marine ecologist and executive director of the Florida-based Shark Research Foundation, who was not involved in the report, told Mongabay. “I think we should not be eating top-level predators,” he said. “Big apex predators are not only rare, but consuming them is bad for our health.”

Research like this can help people make informed decisions about what they eat, but only if they are aware of it, he added. “What is needed now is spreading that awareness,” he said.

Anne-France Mattlet, Tuna Group director of the main representative body for EU fishers, Europêche, rejected the notion that shark meat is unhealthy in an email to Mongabay.

“Consuming predators, including sharks, is not dangerous for your health. It is true that predators contain more mercury than other species, for being at the top of the food chain,” she said, but mercury checks are “rigorous” and occur throughout the supply chain. “The rules and thresholds on mercury exist to protect the consumer. … Any batch of fish that exceeds the permitted levels is either stopped or returned,” she said.

“What concerns us about mercury bioaccumulation is the growing pressure, driven not by science but by misinformation and fake news, which is pushing consumers away from seafood, with harmful consequences for diet and health,” Mattlet said.

Fish and seafood are good sources of protein, essential nutrients and polyunsaturated fatty acids. People should continue to eat them, Mattlet said, citing the European Food Safety Authority (EFSA), which recommended 1-4 servings of fish per week in 2015.

The EFSA also recommended that “species with a high content of mercury in the daily diet should be limited” to protect against neurodevelopmental effects.

A blue shark (Prionace glauca). Image courtesy of Ellen Cuylaerts / Ocean Image Bank.

What should be done?

The report urges governments to strengthen seafood labeling laws, enforce stricter monitoring of mercury levels in shark meat and inform consumers about the hazards of eating large predatory fish. It emphasizes that shark consumption should be minimized or avoided altogether. Münster also noted the need to reduce anthropogenic releases of mercury into the environment.

“[T]he fishing industry, retailers and politicians have a responsibility to educate consumers” so people can make reasoned choices about their mercury consumption, Münster said. “With our hunger for contaminated shark meat and tasteless shark fins, we are endangering our own livelihoods.”

Banner image: A shark is hauled into the hold of the Pedra da Grelo, a Spanish longliner targeting swordfish in the South Atlantic Ocean, in 2019. Image courtesy of © Tommy Trenchard / Greenpeace.

Citations:

Tollefson, L., & Cordle, F. (1986). Methylmercury in fish: A review of Residue Levels, fish consumption and regulatory action in the United States. Environmental Health Perspectives, 68, 203. doi:10.2307/3430265

Myers, G. J., & Davidson, P. W. (1998). Prenatal methylmercury exposure and children: Neurologic, developmental, and behavioral research. Environmental Health Perspectives, 106, 841. doi:10.2307/3434199

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