noun
Hemibarbus barbus; a species of cyprinid fish
A freshwater fish native to East Asia, resembling a carp. The name is usually written in katakana.
ニゴイは川の底でよく見られる。
Hemibarbus barbus is often seen at the bottom of rivers.
釣り人がニゴイを釣り上げた。
The angler caught a Hemibarbus barbus.
コイ (carp) is a more common and widely known fish; ニゴイ is a specific species that resembles a carp.
The name ニゴイ likely derives from 似 (ni, 'resemble') and 鯉 (koi, 'carp'), meaning 'resembling a carp'. The exact historical derivation is uncertain.