What is "oily bitterling"

n. A temperate freshwater fish of the Acheilognathinae sub-family of the Cyprinidae family that is found in central and southwestern Japan.

The oily bitterling (Tanakia limbata) is a temperate freshwater fish belonging to the Acheilognathinae sub-family of the Cyprinidae family. It originates in creeks with fast-running water in central and southern Japan. It was originally described as Capoeta limbata by Temminck & Schlegel in 1846, and has also been referred to as Acheilognathus limbatus and Acheilognathus limbata in scientific literature. The fish reaches a size of up to TL.