Distinguished from other European freshwater species by the following characters: 2 dorsals with the first with 6-8 simple rays, and the second with 2-3 simple and 8-12 branched rays; no spines on first dorsal; no barbels; pelvics not fused into a disc; no lateral line canals; males during spawning period, develop a hump on nape and become black with bright green spots on body and unpaired fins (Ref. 59043).
The invasive Chinese sleeper from the region of Vinnytsya, Ukraine
The Chinese sleeper resembles a perch, ruffe or sculpin. The eyes are placed high on the head which has a rounded snout and projecting lower jaw. There is little or no gap between the two dorsal fins, the front one of which has six to eight spines and the back one nine to eleven soft rays. The anal fin has one to three spines and seven to ten soft rays. The pelvic fins are not fused together which helps to distinguish this fish from the gobies. The second dorsal and the anal fins are both more rounded and shorter than the gobies and the caudal fin is also more rounded. The general colour is brownish with a checker-board pattern of darker marks or dark barring. There are dark lines on the head radiating from the eye. This species can reach a length of 25 centimetres (9.8 in) TL and the greatest recorded weight for a specimen is 250 grams (8.8 oz).
The Chinese sleeper is native to the Far East but appeared in ponds in Eastern Europe in the early twentieth century and has since spread to large parts of the Danube, the Vistula and other river basins where it is considered an invasive species. Its typical habitat is ponds, closed water-bodies and slow-moving streams. The westernmost locality of the Chinese sleeper range is the ponds in the Bavarian Danube basin in Germany.
The Chinese sleeper is an adaptable species and tolerant of widely different conditions. It feeds on insects and their larvae, small crustaceans and fish fry. It spawns in warm shallows among vegetation and the male guards the eggs.
This species is of minor importance to local commercial fisheries and has potential as an aquarium fish. However, introduced populations are of concern as they could become detrimental to the local fauna due to its predatory nature and voracious appetite.
Occurs in lentic waters, lakes, ponds, backwaters and marshes with dense underwater vegetation and avoids river stretches with fast and even slow current (Ref. 59043). Prefers stagnant rivers and bogs (Ref. 80031). Can tolerate poorly oxygenated water and able to survive in dried out or completely frozen water bodies by digging itself into mud where it hibernates. A voracious predatory fish (wide variety of invertebrates, tadpoles and fish) constituting a most serious threat to aquatic fauna wherever it occurs. In small water bodies; known to extirpate almost all other fish species and amphibian larvae. Spawns for the first time at 1-3 years and about 6.0 cm SL. Spawns several potions of eggs in May to June at 15-20°C. Elongated eggs (3.8 x 1.3 mm) with sticky filaments usually deposited in one row close to water surface on underwater structures such as roots, leaves and others. Males guard the eggs and pelagic larvae (Ref. 59043).