Bitterling

Etymology The name is derived from the Greek word rhodeos, meaning “rose” and the Latin amarus meaning “bitter“.   Description It is a relatively small fish from the carp family (Cyprinidae), introduced in Prespa Lakes in the 1990’s The dorsal spines (total): 3; Dorsal soft rays (total): 8-10; Anal spines: 3; Anal soft rays: 8-10; Vertebrae: 34 - 36. Caudal fin with 19 to 20 soft rays.   Biology It occurs most abundantly in still or slow-flowing water with dense aquatic vegetation and a sandy-silty bottom, such as lowland ponds, canals and slow-flowing rivers, where mussels are present. It is also found amongst plants over sand and muddy bottoms in shallow waters. It is remarkable for its habit of deposing its eggs in the cavity of bivalves (Unio). It feeds mainly on plants and to a lesser degree on worms, crustaceans, and insect larvae. The life span is exceptionally up to 5 years but most individuals do not survive the year of their first reproduction and population sizes fluctuate greatly over the years. Of interest is that the fish was formerly used for pregnancy testing of humans. A urine sample from pregnant women was injected into female fish and this protruded their ovipositors if the test was positive.   Distribution Europe: Basins of North, southern Baltic, Black, western and southern Caspian and Aegean Seas (from Maritza to Struma drainages); Mediterranean basin, only in northern Rhône and Drin drainages. Abundant and expanding in most of its range, but locally threatened by water pollution, weed clearing, and stocking of predatory fish.   Fishing significance No significance. In Prespa Lakes the population is very low.   Impact Interferes with the native fishes on food competition.   Management Ameliorative fishing.