The spiny stickleback is a brownish fish between 5 and 8 cm in size that lives in the Chestnut River. Despite its small size, its life cycle is very interesting. In addition, its appearance is unusual because it lacks scales and instead has bony plates. Its name is due to the fact that it has three erectile spines at the will of the fish, with which it defends itself from enemies.
During reproduction (from March to July) the female has a rounded belly and a silvery color. The male acquires a very striking coloration, with a metallic blue back, red abdomen, golden gills and large green eyes.