A predominantly riverine fish preferring clear, well-oxygenated, running waters with substrates of sand, gravel, rock or mud, where adults tend to form schools just above the substrate in slower-moving sections.

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.

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.

A. macropterus appears in the ornamental trade on an irregular basis and should only be considered by more experienced aquarists with sufficiently large facilities.

Given its wide geographical distribution there is a possibility that it represents a group of closely-related species, with genetic studies indicating the existence of several distinct clades.

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…

This species is frequently confused with C. argus but can be distinguished by the following characters: dorsal-fin rays 38-45 (vs. 47-50 in C. argus); anal fin rays 26-29 (vs. 31-36); lateral line scales 50-56 (vs. 60-66); 2-3 rounded blotches on caudal peduncle (vs. no blotches on caudal peduncle).

It is widely-distributed in Pacific coastal drainages of southeastern China (e.g. the Yangtze, Minjiang, Hangjiang River, and Pearl (Nanjiu…

Some wild populations have evolved a complex amphidromous breeding strategy in which adults live and spawn in freshwater or brackish streams and the pelagic post-hatch larvae are washed downstream to the sea where the post-larval fry spend the first part of their life developing in estuarine nursery zones under brackish to full marine conditions.

Once they reach a certain stage of development they begin to migrate upstream with some mov…

There are a number of unidentified species within the grouping of which several are referred to using a two-letter code based on their respective colour pattern for ease of reference, with ‘CB’ shorthand for ‘cross band’, for example.

R. sp. ‘CB’ is the commonest member of the grouping in Japan but has not yet entered the international aquarium trade as far as we know.

This species is largely unsuitable for the home aquarium given its eventual size and natural behaviour, and we know of only a handful of private aquarists with the facilities required to house it long-term.

It’s currently illegal to import or own the species in the United States, United Kingdom and several other countries unless in possession of an official license.