The flounder is a type of flatfish, known for its distinctive flat body shape. It has adapted to living on the seabed, and its unique appearance allows the flounder to blend seamlessly with its surroundings. Flounders are widely distributed across the globe, inhabiting diverse coastal waters.
Unique Flounder Features
The flounder’s most recognizable physical characteristic is its compressed, disc-like body. At birth, a flounder larva resembles a typical fish, with one eye on each side of its head, and it swims upright. As the fish matures, it undergoes a metamorphosis: one eye migrates across the top of its head to join the other eye on what becomes the upward-facing side of its body. This eye migration allows both eyes to observe the environment above the flounder as it rests on its side.
This transformation also involves the loss of the swim bladder, an organ that helps most fish control buoyancy, and the side of the body that rests on the seabed loses its pigmentation. The flounder possesses an ability to change its color and pattern rapidly. This camouflage is achieved through specialized skin cells called chromatophores, which allow the flounder to mimic the texture and coloration of the sandy or muddy seabed, providing effective concealment.
Where Flounder Live
Flounders are demersal fish, meaning they primarily live on or near the bottom of aquatic environments. They show a preference for soft, sandy, or muddy substrates found in coastal waters, estuaries, and shallow areas of the ocean. Their flattened bodies and camouflaging abilities enable them to bury themselves in the sediment.
While many flounder species are found in marine (saltwater) environments, some can inhabit brackish water, such as estuaries, or even freshwater for certain species. Their distribution is widespread, with various species found in oceans worldwide, including the Atlantic and Pacific. Flounders are ambush predators, lying camouflaged on the seabed and waiting for prey, such as small fish, crustaceans, and worms, to pass by.
Different Kinds of Flounder
The term “flounder” refers to numerous species of flatfish, belonging to several distinct families within the order Pleuronectiformes, such as Pleuronectidae and Paralichthyidae. A key distinction among these species is whether their eyes migrate to the right or left side of their head during metamorphosis, categorizing them as “right-eyed” or “left-eyed” flounders. For instance, the family Pleuronectidae typically comprises right-eyed flounders, while Bothidae and Paralichthyidae are generally left-eyed.
Common examples of flounder species include the Summer Flounder (Fluke), which is a left-eyed species prevalent in the Western Atlantic, and the Winter Flounder, a right-eyed species found along the Atlantic coast. The European Flounder is another well-known species, inhabiting European waters. Larger flatfish, like the Pacific Halibut, are also part of this diverse group, demonstrating the wide range in size and appearance among fish collectively referred to as flounders.