Mongolia

Native to continental China, the Korean peninsula, and southern Japan. Type locality is given only as 'Lakes and rivers, northern China', with the type series possibly originating from the Pai-ho River near Beijing. It has been widely introduced and is considered invasive elsewhere, including the Mekong river basin (records from Laos and Thailand), Salween river (Myanmar), northern Japan, Taiwan, Turkmeni...

Despite being a wholly unsuitable aquarium subject, C. idella is often traded as such, with an albino form having been developed specifically for the ornamental market. Individuals which have outgrown their aquarium or pond should never be released into natural waters, either, since this species has proven capable of causing serious environmental damage under a wide range of climatic conditions.

The adult size and power of this impressive predator preclude it from consideration as an aquarium species, but young individuals are nevertheless available in the ornamental trade on an irregular basis therefore it is included here. It is an entirely unsuitable choice for the home aquarium and the majority of zoos and public aquaria would probably struggle to maintain it in adequate conditions.

This species can be distinguished from other members of the genus by the following combination of characters: absence of dark spots on body in adults; body elongate with slightly convex dorsal profile; head longer than body is deep; snout much longer than postorbital head length; lips well developed, lateral lobes of lower lip broad and thick with folds, median process small; barbel thickness shorter or equal to eye diameter; dorsal spine strong, ⅔ of HL; dorsal-fin origin closer to tip of snout than caudal-fin base base; 15+ gill rakers; 6½ branched anal-fin rays; posterior simple dorsal-fin rays ossified and spinous.

Widepread in eastern Asia between the Yangtze and Amur river basins, including China (mainland and islands of Taiwan and Hainan), Korea, Mongolia, Russia, and Japan. It probably been introduced to Vietnam and Laos, or records from these countries represent another species.