The Etheostoma caeruleum is very sensitive to pollution and silt, staying in clean pollution free water
Rainbow darters are easily identified by three dark spots on the back; also they have blue and orange in their dorsal and anal fins
Rainbow Darters have 8-13 vertical bands along the side of their body. These bands are blue on males and brown on females and young. Males have no teardrop shaped marking under the eye. Females may have a short poorly defined teardrop. The anal fin of males has some red or orange in the center surounded by blue. The blue coloration on the body intensifies on breeding males and some individuals can look almost black. Rainbow darters are most similar to orangethroat darters. Both male and female orangethroat darters have a well defined teardrop under the eye and males have a solid blue anal fin with no red or orange like the rainbow darter.
Rainbow darters prefer riffles of moderate gradients composed primarily of gravel and small cobble. They are most abundant in medium to small sized (20-60 ft wide) streams. However, they are not usually found in very small headwater streams and small numbers can be found in even the largest rivers in Ohio. They are one of the most wide spread darter species in Ohio and can be found through out the state.
Breeding takes place in riffles from mid April to mid May. Females deposit three to seven eggs in the gravel and the male fertilizes them. This can be repeated many times over several days during their breeding season. A single female can lay about 800 eggs in a single breeding season.
