Of all the amazing fish in New England’s waters, flounder may be among the strangest. These flat fish spend most of their lives on the seafloor, where they eat small fish and crustaceans. To help with this horizontal lifestyle, flounder have evolved a couple of characteristics that help them thrive on the ocean bottom. First, they’re camouflage experts—most species of flounder have elaborate patterns that blend in with their habitat, and many will burrow and hide in soft sand and mud. Some flounder can even change colors, like ocean chameleons. Second, flounder are perfectly adapted to lie flat on the seafloor. Although they are born with one eye on each side of their head, as they mature, one eye migrates to the other side of their body, allowing them to lie on one side without getting an eye full of sand.
Flounder are found in coastal waters throughout the Northern Atlantic and Pacific, but some flounder species are particularly important to fishermen in New England. Commercial fishermen here catch witch flounder, summer flounder, windowpane flounder, and winter flounder like the one in the picture at the top of this post. One species, yellowtail flounder, is especially important to fishermen, because it’s often caught accidentally when targeting other fish species or scallops.
Flounder aren’t only important to fishermen and seafood lovers,. They can also serve as indicators of the environmental health of their habitat. Because flounder live and eat close to the seafloor, they are particularly sensitive to contaminants caught in marine sediments, like mercury, lead, and pesticides. During the worst years of pollution in Boston Harbor, flounder there had the highest levels of liver lesions and tumors in the Northeast. As the cleanup of Boston Harbor has progressed, rates of liver disease and deformities have dropped quickly, and even flounder living in the Harbor are within safe FDA limits for toxins like DDT and mercury. Not only do the flounder benefit from a cleaner harbor, but they can also teach us a lot about the health of our oceans!