Wels Catfish

Description This is a large catfish found in wide areas of central, southern, and eastern Europe, and near the Baltic and Caspian Seas. It is a scaleless fresh and brackish water fish recognisable by its broad, flat head and wide mouth. Wels catfish can live for at least thirty years and have very good hearing. It is distinguished from all other freshwater fish in Europe by the following unique characteristics: two pairs of large barbells; anal fin with 83-91½ rays; large body, depressed head; dorsal fin with 2-4½ rays; caudal fin rounded or truncate; no adipose fin; and anal rays almost touching caudal. Caudal fin with 17 rays. It has very slippery green-brown skin. Its belly is pale yellow or white. The colour varies with the aquatic environment. Clear water will give the fish a black coloration while muddy water will often tend to produce brownish specimens. The weight and length are not correlated linearly, and also depend on the season.   Biology This fish inhabits large and medium sized lowland rivers, backwaters and well vegetated lakes. It occurs mainly in large lakes and rivers, though occasionally enters brackish water in the Baltic and Black Seas. The female produces up to 30 000 eggs per kilogram of body weight. The male guards the nest until the brood hatches, which, depending on water temperature, can take from three to ten days. If the water level decreases too much or too fast the male has been observed to splash the eggs with the muscular tail in order to keep them wet. With a possible total length of up to 3 m and a maximum weight of over 150 kg it is the largest freshwater fish in the region. Most wels catfish are about 1.3-1.6 m long; fish longer than 2 m are normally extremely rare. At 1.5 m they can weigh 15–20 kg and at 2.2 m they can weigh 65kg. They feed on worms, gastropods, insects, crustaceans, and fish including other wels catfishes; the larger ones also eat frogs, mice, rats and aquatic birds such as ducks. It attains first sexual maturity at 2-3 years of age.   Distribution Europe and Asia. North, Baltic, Black, Caspian and Aral Sea basins, as far north as southern Sweden and Finland; Aegean Sea basin in Maritza and from Struma to Sperchios drainages; Turkey. Absent from the rest of Mediterranean basin. It is now widely introduced and translocated throught Europe and Lake Balkhash basin in Kazakhstan. Several countries report adverse ecological impacts after its introduction. It was introduced into Macro Prespa in 1986. Fishing significance Although of high commercial value, in Prespa Lakes its population is very low and thus the fishing is low rated.