Identification
The Chinese sleeper is a stocky, big-headed fish of 15 to 25 cm with a wide, flat head and large mouth. Color varies from dark brown to olive green with irregular dark blotches. During spawning, males turn nearly entirely black. The pelvic fins are not fused into a sucker (unlike true gobies).
Ecology
The Chinese sleeper is an exceptionally tough fish. It can breathe atmospheric air through its gills and survives in deoxygenated water. Even more remarkably, the species can survive being frozen in ice — unique among European freshwater fish. It is an aggressive predator feeding on eggs, larvae, invertebrates, and small fish. Males guard the nest fiercely.
In the Netherlands
The Chinese sleeper is an invasive exotic from the Amur basin in East Asia. Through the aquarium trade and deliberate releases, it has spread across Eastern Europe and is advancing westward. Few records exist in the Netherlands so far, but its extreme tolerance for cold and oxygen deprivation makes establishment a real risk. The species can cause serious damage to native fish populations.
