olive in color with numerous "w-shaped" markings along the sides; one of 16 species of darters in Iowa; reaches a maximum length of about 2 1/2 inches
statewide (with the exception of the southwest corner of the state) in medium-sized streams and some lakes
chironomids, tiny crustaceans, small insect larvae
darters play an important role in aquatic food chains and are some of the most colorful fish in Iowa
The range of the Johnny darter is quite extensive, rivaling that of logperch. In Iowa, it reaches its greatest abundance in the small creeks and streams of the northeast region. It is also common in some of the natural lakes and is occasionally sampled in man-made lakes.
The Johnny darter is a small member of the darters, reaching a maximum length of approximately 2 1/2 inches. It is olive in color with numerous, conspicuous w-shaped markings along the sides. The dorsal fin contains 12 rays, the anal has 8 rays; there are usually about 50 scales along the lateral line, and the breast and cheeks are scaleless.
Habitat preference is quite diverse. They are found in streams of various size, gradient, substrate and clarity. Of all the darter species, it may be the most tolerant of diverse conditions. It is not a riffle species and is frequently encountered in small to medium-sized streams of moderate clarity, where it lives in pools over sand or solid bedrock.
Spawning activities of this fish have been examined intensively. The males establish territories around partially embedded rocks in the spring when the water temperature approaches 60 degrees F. A nest site is prepared by turning upside down and rubbing the area with the caudal, anal and pelvic fins, while balancing with the aid of the pectorals. Gravid females are approached with fins lowered and are led beneath the rock where nest polishing is resumed. The female may then join the male, head to head, and deposit 30 to 200 eggs in the nest. Females may lay 5 or 6 egg clutches, and males sometimes accumlate a thousand or more eggs from several females. Males then guard the eggs until hatched.
Chironomids, tiny crustaceans and small insect larvae are the primary food items of Johnny darters.