The rosy bitterling or Tairiku baratanago (Rhodeus ocellatus) is a small freshwater fish belonging to the family Cyprinidae (carp), native to East Asia from the Amur River basin to the Pearl River basin.

However, males change to a reddish (sometimes purple) color during the spawning season (March to September) which functions to attract females.

The female rosy bitterling has a unique pipe about the same length as its own body, used for laying eggs on a specific spot of mussels.

A male spawns into the gill cavity of the mussels right after a female lays eggs to ensure fertilization.

In 1942, rosy bitterling were accidentally introduced with grass (Ctenopharyngodon idellus) and silver carp (Hypophthalmichthys molitrix) from mainland China.