European Flounder, Platichthys flesus

The European flounder (Platichthys flesus) is a species of fish inhabiting the White, Mediterranean and Black Seas.  It is native to the north eastern Atlantic Ocean and the Mediterranean Sea and has been introduced to the United States and Canada possibly by ballast water (water stored in the hull of a ship for stability). It has also been introduced to Iran.

It is normally found at low depths to 330 feet. This species prefers sandy, shingle or muddy bottoms to camouflage itself from predators. It is also sometime found in freshwater estuaries and rivers.

It is a flat fish with an oval-shaped body. The width of the body is normally about half its length, which averages 20 inches. The maximum recorded length is 24 inches and record weight is 31 pounds. A small mouth sets at the end of a bluntly pointed snout. It has rough skin with small prickly extensions at the base of its fins and large scales beside the lateral line on its back.

The upper color is fawn, olive green or pale brown with spots and large patches usually dark brown. There may also be some irregular reddish spots mixed in. The under side of the fish is a pearly-white. There is a nearly straight lateral line along the middle, on the upper surface that curves around the pectoral fins. A dorsal fin stretches from the head to beside the tail’s base. The fin contains 53 to 62 soft rays but no spines. The anal fin stretches the length of the body and has 37 to 46 soft rays and no spines. The tail fin is squared-off.

Unlike other species of fish, the European flounder swims mostly on its right ride, about 30 percent swim on the left side. What appears to be the top of the fish, is actually the side.

During the day, the European flounder rests on the sea floor. It feeds on mollusks, invertebrate, shrimp, polychaete worms and smaller fish.

It will leave freshwater in the autumn and migrate to deeper ocean water in the winter. In the spring, it will travel to spawning grounds, three or four miles a day. Between February and May, the female lays about a million eggs that are lighter than water and will float on the surface. The male’s sperm will also float to fertilize the eggs. In about six to eleven days, the eggs hatch and the larvae are planktonic, drifting on the surface toward the coast. The juvenile will stay in shallow water until mature when males reach 4.5 inches and females 7 inches.

The flounder is taken for human consumption, mostly around the Baltic Sea, The Netherlands and Denmark. Bottom trawling is preferred and in 2010 about 19,000 tons were taken worldwide.  It is marketed fresh and frozen and can be cooked in a variety of ways.

The International Union for Conservation of Nature has the European flounder listed as least concern because of its large population and range. The population may be decreasing, but not substantial enough to change its status.

Image Caption: European flounder (Platichthys flesus). Credit: Tiit Hunt/Wikipedia (CC BY-SA 3.0)