高丽鱊 · Korean Bitterling

Overview

Tanakia signifer is a bitterling endemic to the Korean Peninsula. Living freshwater mussels are essential to its reproduction. It is not a regular ornamental-trade species, although captive populations are maintained in South Korea.

Distribution & habitat

Its range covers southern North Korea and northern South Korea. South Korean records are restricted to the Han River system, where numerous local populations have disappeared. Typical habitats are cool, clean, relatively shallow flowing waters over coarse sand or gravel, bordered by vegetation.

Breeding

Bitterlings place their eggs between the gill lamellae of living mussels. A breeding female develops a long ovipositor and inserts eggs through the host's exhalant opening. The male releases sperm near the inhalant opening and vigorously excludes rival males. Embryos and young fish remain within the host before emerging as free-swimming fry.

At least two mussel species serve as hosts for this fish, which does not establish that any freshwater mussel is suitable. Development times and spawning seasons differ among bitterling species. Maintaining the host and its clean-water habitat is therefore inseparable from supporting successful reproduction.

Notes

A dark brown dorsal fin with a pale outer band is a useful feature to observe; dark longitudinal stripes are absent from the body and tail fin. Older accounts use a different generic placement, so locality and scientific synonyms are more informative than a general bitterling label.