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Monday, September 1, 2008

What are flounder fish ?

The flounder is much more than an exciting sports fish or a delicious food fish. This amazing creature from the Pleuronectiformes order goes through an incredible transformation that takes it from a normal appearing fish at birth to a round, flat fish in adulthood. These interesting fish prefer to make their habitat at the bottom of most warm or moderate oceans but can be found in waters throughout the world including some arctic areas. They are mostly found in the shallow waters along the coast where they manage to blend so well with their surroundings that they are hard to see. Depending on the species, some flounder, such as the sole, are only inches long while others, such as the halibut reach several feet in length. In fact, in some species of flounder the only fishes in the sea that is larger are some of the larger sharks such as the whale shark. Flounder are found in the Pleuronectoidei suborder, which has four families and close to one hundred species. The most distinguishing characteristic of the flounder is the shape of their bodies which it is believed has evolved over the years from a more perch like body shape to the extensively round and flattened body of a bottom dweller. One of the more interesting aspects of this type of evolution is that it begins when the flounder has just hatched and continues until adulthood is reached.

In most species of flounder spawning takes place during the warmer months of the year. While some species migrate from deeper waters to the coastal spawning grounds others move along the coast to their chosen spawning site. After spawning, the eggs are deposited by the females of the species where they float in the water aided by a tiny oil bubble in each egg. With some species they remain near the bottoms within an area of vegetation, while in other species the eggs rise to the shallow surface. Once they hatch the tiny larvae have the appearance of most other fish with the tiny eyes on either side of its head. The young fish will drift along in the water freely feeding on plankton and tiny crustaceans. During this time they continue to grow and a kind of winding together occurs in the intestinal tract that creates a change in the bones of the skull and mouth. In turn, this begins a movement of the eye that causes it to migrate to the left or right side of the head area. The direction this eye movement takes is determined by a necessity for balance on a specific side of the body, but is also genetically preordained. Thus, after a few months the young fish will have evolved to be either in the left eye or right eye family of flounders. As the young flounder reaches the adult stage it will move to the bottom of its habitat where it adapts to a bottom dwelling existence. This will include a change in color that blends with its environment on the upper side of its body. Depending on the habitat, this camouflaging coloration may be mottled to match the different colors along the bottom or in some areas with sandy bottoms, may be solid.

Some species of flounder are known to further camouflage their bodies from predators by digging themselves into the bottoms using their fins to toss the bottom matter over their bodies. Interestingly, most species have protruding eyes that move as they watch for predators or prey. Often the only parts of this bottom dweller that can be observed are the eyes. When disturbed this amazing fish will quickly swim away using a kind of fluttering motion that throws up a cloud of silt around its body. After it has reached a safe distance from the disturbance, it will settle back on the bottom and quickly become invisible. While some species of flounder have diets that consist mainly of what ever they can sift from the bottom of their habitat, others are known to ingest whole fish including those of their own species. Although not all species of flounder are considered good food fish, the tasty meat of some species have made their main predator man.

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