The johnny darter is found from Saskatchewan and Colorado to the Atlantic seaboard and from Hudson Bay south to the Gulf Coast drainage systems. They are the most common darter in Minnesota and Ohio. The johnny darter can reach a length of 7.2 centimetres (2.8 in) TL though most only reach about 3.9 centimetres (1.5 in). Males weigh a little over 2.0 grams, and the females weigh about 1.6 grams. These small, slender fish have brown to yellow scales, paler sides, and whitish bellies. They have no bright colors and generally just have brown or black markings on a lighter tan background. These markings are usually a series of black w or x shapes along their sides running along their lateral lines. On the fish, the opercles (or bony areas forming the gill covers) have scales, whereas the preopercles (bone at the start of the cheek), napes, and breasts are scaleless. The johnny darter has two dorsal fins, the first has hard (spinous) rays, while the second is soft-rayed (flexible). The pectoral and pelvic fins are close to each other behind the gills. The pectorals are large and fan-like and are situated on the lower sides of the fish. The pelvic fins are small and round and situated in the ventral side of the fish. They have a rounded tail fin on the ventral side, as well.
