Flounder Fish

The flounder fish is a flatfish that is found in the Northern Atlantic and Pacific Oceans, Canada, and the United States.

There are many species of the flounder fish. These flatfishes belong to the Pleuronectidae, Paralichthyidae, Bothidae, and Achiropsettidae families. Flounders are mainly differentiated according to the location of their eyes and color. The Pleuronectidae family consists of species who have eyes on the right side; whereas species from the Bothidae and Paralichthyidae family have their eyes on the left side.

The Pleuronectidae family includes flatfishes like the winter flounder (Pseudopleuronectes americanus), starry flounder (Platichthys stellatus), and the European flounder (Platichthys flesus). The peacock flounder (Bothus lunatus) and summer flounder (Paralichthys dentatus) are some flatfishes from the Bothidae and Paralichthyidae family. The normally small flounders of the Achiropsettidae family are found in the Antarctic waters.

Structure of the Flounder Fish
Flounders are flatfish that can evolve into different sizes. Mature flounders can weigh from 20 pounds to 600 pounds. Generally, their length and weight depends on the species they belong to. Some flounders like the sole fish are only inches long; while others like the halibut can grow up to a greater length. For some flounder species, the only fish in the sea that are bigger than them are the whale sharks. Flounder fish have fins across the upper parts and also underneath their bodies. They resemble a flat, circular ball with fins circling around. These fish are normally brown in color, but can acquire a variety of colors like red, orange, green and blue.

Physical Transformation
In its lifetime, a flounder fish undergoes unusual transformation in its structure. When the egg hatches, like most other fish, it has an eye on any one side of its head. After a few days, it begins to lean to one side and the eye on that side migrates to the side with the other eye. In this way, the side that has both eyes becomes the top of the fish. It becomes a fish that lives at the bottom, with the color of the eyeless side fading, and becoming the bottom of the fish. With this transformational development, there are many other complicated changes that occur in the nerves and digestive system of the fish. There are also some visible changes in the muscles and bones. This migratory pattern of the eye is genetically influenced.

Food and Habitat
Many species make their home in warm or moderate oceans, but quite a few of them are also found in oceans around the world including the arctic waters. They are predominately found in the shallow waters along the coast, where they blend so well with their surroundings that they are hardly visible. They like to eat a wide range of ocean foods. Some of them habitually eat other fish, while others eat worms, mollusks, and crawfish. These fish seem to be fairly choosy on what they want to eat.

Breeding
In most of the flounder species, spawning occurs during the hotter months of the year. Some species migrate from deeper waters to the coastal breeding grounds, others move along the coast to their preferred spawning site. After spawning, the eggs are deposited by the females where they float in water due to a small oil bubble present in every egg. In case of some species, the eggs remain near the bottom within the vegetation area, while in other species the eggs rise to a shallow surface. After hatching from the eggs, the tiny creatures appear like most other fish with eyes on any one side of their head. The newborns drift along in the water, freely feeding on plankton and midget crustaceans. As they reach their adulthood, they move to the bottom of their habitat where they adapt to a bottom-dwelling existence.

Behavior
Depending on the home ground of flounder fish, the camouflaging coloration may be dappled to match different colors along the bottom or in some areas with sandy bottoms. Some flounders camouflage their bodies and appear invisible to predators as they dig themselves into the bottom, using their fins to settle the ground material over their bodies. Most species have outward-bulging eyes that move as they watch for predators or prey. Most often, the only part of this bottom-dweller that is visible are its eyes. If it is disturbed, it rapidly swims away in a motion that throws up all the bottom silt around its body. After it reaches a safe place away from the disturbance, it settles back on the bottom and becomes invisible.

Many of the flounder fish species are on the verge of extinction due to overfishing by fishermen.