The blue breast darter is a small, colorful fish that usually grows to about three inches in length. It can be distinguished from other darters by its blunt, rounded snout, and its gill covers which are not connected across the breast.
The blue breast darter is olive-green in color and there is a broad light band adjacent to the dark edge of the second dorsal (back), anal (bottom rear), and caudal (tail) fins. Breeding males are extremely colorful, with orange-tinted dorsal fins, numerous small crimson spots on the sides and a bright blue breast - hence its name.
The blue breast darter prefers fast-flowing sections of large streams where the substrate consists of sandy gravel and large stones. The darter uses the stones for protection, and is usually found behind, beside, or under them. The blue breast darter is rare in New York, found only in the upper reaches of the Allegheny River and a tributary.