Metzia

Metzia bounthobi is a cyprinid known only from the Nam Ou River basin, a Mekong tributary in northern Laos. It has been collected from hill streams with clear, slow to moderately fast-flowing water. It differs from all its congeners in having more branched anal-fin rays and more lateral line scales, and the genus itself remains unresolved in taxonomic terms.

Metzia formosae is a small cyprinid from northern Taiwan, Hainan, Hong Kong, southern China and northern Vietnam. It is identified by its upturned mouth and a black stripe along the flank from the gill opening to the caudal-fin base. It inhabits slow-moving to still, well-vegetated waters, including streams, rice paddies, ditches and canals. The genus remains unresolved in taxonomic terms.

Metzia lineata is a cyprinid from southern China, Hainan, Hong Kong and the Red River basin of northern Vietnam. Populations from the upper Pearl River and from Vietnam differ from those elsewhere, which suggests several species may be included under the name. It lives in slow-moving to still, well-vegetated waters. It has been introduced to other river systems in China and to northern Laos.