【Reading】げんごろうぶな

【English Name】Japanese crucian carp

Gengoro-buna (written 源五郎鮒) is a freshwater fish belonging to the family Cyprinidae, genus Carassius, known as a species endemic to Lake Biwa and the Yodo River system. Its great outward characteristic is its tall body and a contour reminiscent of a rhombus when viewed directly from the side. The position of the eye is somewhat low, and its maximum total length reaches about 60 cm.

Its diet centers on phytoplankton, and its breeding season is around April to June. Spawning takes place in shallows thick with aquatic plants and near the bases of bankside plant roots. Its growth rate is relatively fast, said to reach about 30 cm in body length in around three years, and there are reported cases of long-lived individuals surviving for several decades.

Individuals that have undergone aquaculture and selective breeding are known as hera-buna (kawachi-buna), and aquaculture has historically flourished centered on the Kawachi region of Osaka. As an ingredient, it is used in dishes such as arai (sashimi), funakoku (a miso-based soup), and kara-age. Also, in response to the decline of the nigoro-buna endemic to Lake Biwa, there are increasing occasions where it is used as a substitute ingredient for funa-zushi (fermented crucian carp sushi).

On the Ministry of the Environment Red List it is classified as Endangered (EN, category IB), with the loss of reed beds due to lakeshore development and predation pressure from invasive fish cited as major threats.