Shark meat carries dangerously high levels of mercury, poses unique food safety risks, and eating it contributes to the decline of species that are critical to ocean ecosystems. While shark is technically edible and consumed in some cultures, the FDA places it in the “Choices to Avoid” category for mercury, its highest warning tier. The average mercury concentration in shark meat is 0.979 parts per million, with some samples reaching as high as 4.54 ppm. For context, most fish considered safe to eat regularly contain well under 0.1 ppm.
Mercury Builds Up in Shark Meat
Sharks are apex predators, meaning they sit at the very top of the ocean food chain. Every fish a shark eats has already absorbed mercury from the water and from its own prey. This process, called biomagnification, means toxins concentrate more intensely at each step up the food chain. By the time you reach a large shark that has spent decades eating other predatory fish, its muscle tissue contains mercury levels many times higher than the small fish at the bottom of the chain.
The form of mercury found in shark meat is methylmercury, which is especially harmful because your body absorbs it easily and eliminates it slowly. Once in your system, methylmercury disrupts your cells in several ways. It binds to protective molecules your body relies on to neutralize harmful compounds, depleting those defenses and leaving cells vulnerable to damage. In the brain, it interferes with how nerve cells communicate by causing a buildup of signaling chemicals between neurons, which can overstimulate and kill those cells. It also disrupts the energy-producing machinery inside cells, generating a cascade of damaging molecules. The result, with enough exposure, is neurological harm: numbness, vision changes, difficulty with coordination, and cognitive impairment.
The FDA and EPA specifically advise pregnant and breastfeeding women and children to avoid shark entirely. Developing brains are far more susceptible to mercury damage. But high mercury levels aren’t just a concern during pregnancy. Adults who eat shark regularly can accumulate enough methylmercury to experience symptoms over time, since the body takes weeks to clear even small amounts.
Shark Flesh Breaks Down Differently
Beyond mercury, shark meat has a built-in chemistry problem that most other seafood doesn’t. Sharks use urea, a waste product that mammals excrete in urine, to regulate the salt balance in their bodies. Their muscle tissue contains urea concentrations of roughly 200 to 460 millimoles per liter, far higher than any bony fish. Alongside urea, their flesh contains a compound called TMAO that counteracts the urea’s tendency to break down proteins while the shark is alive.
The moment a shark dies, bacteria start converting that urea into ammonia. This is why fresh shark meat can quickly develop an overpowering smell that ranges from harsh chemical to outright rotten. If the meat isn’t bled, gutted, and processed extremely quickly after the catch, the ammonia buildup makes it unpalatable and potentially sickening. Proper handling can minimize this, but it requires more care and speed than most commercial fish processing demands, which is one reason shark rarely appears in typical seafood markets.
Ciguatera Poisoning Is a Real Threat
Large reef-associated sharks can also carry ciguatoxins, the same family of toxins responsible for ciguatera fish poisoning in tropical species like barracuda and grouper. Reports of severe food poisoning from shark meat go back to the 1940s, but scientists only recently confirmed ciguatoxins as a cause. In 2013, a bull shark consumed in Madagascar poisoned and killed 11 people. Laboratory analysis identified multiple ciguatoxins in the shark’s tissue, including two previously unknown variants.
Ciguatera symptoms are predominantly neurological: tingling, temperature reversal (cold feels hot and vice versa), nausea, and in severe cases, respiratory failure. There is no way to detect ciguatoxins by looking at, smelling, or cooking the meat. Cooking does not destroy these toxins. This makes shark from tropical waters a particularly unpredictable risk, since there’s no reliable way for a consumer to know whether a given piece of meat is safe.
Shark Populations Can’t Sustain Heavy Fishing
Sharks reproduce slowly. Many species don’t reach sexual maturity for a decade or more, and they produce far fewer offspring than bony fish. This makes shark populations extremely vulnerable to overfishing. Over the past half century, coastal apex shark populations have declined dramatically. White shark catch rates along the Queensland coastline in Australia dropped by 92% over five decades. Many large shark species that were once historically abundant are now classified as Endangered or Vulnerable by the International Union for Conservation of Nature.
Removing apex sharks doesn’t just affect shark numbers. It reshapes entire ecosystems. Sharks regulate the populations of mid-level predators and influence nutrient transfer across different marine habitats. When shark populations collapse, the animals they once kept in check can explode in number, overgrazing their own food sources and triggering chain reactions that degrade coral reefs, seagrass beds, and other coastal ecosystems.
In the United States, the Shark Conservation Act of 2010 requires that all sharks be brought to shore with fins naturally attached, effectively banning the practice of finning, where fishers slice off the fins at sea and discard the body. Possessing, selling, or transporting detached shark fins is prohibited under federal law, with narrow exceptions for scientific research and subsistence use. These regulations reflect how seriously depleted many shark populations have become.
Some Cultures Have Found Workarounds
Despite all these risks, shark is eaten in parts of the world where traditional preparation methods address some of the problems. The most famous example is hákarl, the Icelandic fermented shark. Greenland shark flesh is toxic when fresh due to its extremely high urea and TMAO content. To make it edible, the meat is buried in gravel pits and left to ferment for six to twelve weeks, then hung to dry outdoors for several more weeks to months. This extended process breaks down the harmful compounds enough that the meat becomes safe to consume, though the powerful ammonia flavor makes it an acquired taste even by Icelandic standards.
In other regions, particularly parts of Asia, South America, and the Pacific Islands, shark meat is consumed after careful bleeding and soaking to reduce urea. These preparations can make the meat palatable, but they do nothing to reduce mercury or ciguatoxin levels. The fundamental health risks remain regardless of how the meat is cooked or prepared.