The Popular Fish You Shouldn't Eat The Skin From

There are dozens of ways to enjoy fresh fish. Sometimes it's chopped and served in a poke bowl, other times it's added to soup. Sometimes it's pan-seared in butter, other times the whole fresh fish is served with the nutrient-rich head still attached. Chefs and fishing enthusiasts can take creative liberties with the ways they prepare a catch, but while eating the skin of some fish is fairly common, there are other kinds you're better off avoiding for a very good reason. We reached out to Ed Cotton, chef and partner at Jack & Charlie's and Leonetta in New York City, to see which ones to avoid.

Cotton says that the skins of "marlin, shark, sword, tilefish, and king mackerel are very high in mercury and therefore should not be overconsumed." In the grand scheme of fish species, this list doesn't encompass too many. You could technically still consume plenty of other fish skins, but according to Cotton, these species' skins aren't safe to consume in large portions, so it's best to just get rid of the skin ahead of time. He also suggests that you avoid eating skate fish skin, since "it contains these thorn-like barbs on the outside of the fish."

While mercury is a naturally occurring element, inorganic mercury forms when the element reacts with another substance. When inorganic mercury dissolves in water, it turns into methylmercury, the most toxic variation of mercury. Methylmercury gets stuck in phytoplankton, small fish eat the phytoplankton, those smaller fish are eaten by larger fish, and those larger fish are eaten by even larger fish until there's a massive buildup of methylmercury in their tissues. Accumulation is highest in fish at the top of the food chain.

This methylmercury buildup is what makes some fish skin unsafe for human consumption in large amounts. The fish skins that Chef Ed Cotton recommends avoiding — marlin, shark, swordfish, tilefish, and king mackerel — belong to some of the largest fish in the ecosystem and therefore contain high levels of methylmercury, though tilefish from the Gulf of Mexico, specifically, are the edible fish with the highest level of mercury contamination. Over-consuming mercury can lead to serious health effects in humans, such as nervous system problems. 

Tremors, headaches, and memory loss are just a few of the symptoms, not to mention the potential effect high mercury levels can have on the cardiovascular system. It can also cause development issues for unborn fetuses and children, hence why pregnant women are advised to be cautious with seafood. This isn't to say that fish skins need to be avoided altogether, though. You can still make a mean pomegranate-glazed salmon with the skin attached if you feel like it — in fact, eating salmon skin is a great way to get extra omega-3 fatty acids and flavor — but maybe don't try to mimic that recipe with a swordfish.