Darters are an incredibly diverse and colorful group of freshwater fish, which rival saltwater fish in brilliance. They are actually small representatives of the perch family (Percidae) and are closely related to yellow perch and walleye. The darter group consists of approximately 160 species, all of which are restricted to North America. As such, they represent 20 percent of all fish in the United States.
Identification
Three genera of darters are recognized: Percina, which includes roughly 40 species; Etheostoma, which includes roughly 112 species; and Ammocrypta, with 7 species. The genus Percina contains the largest darters. Most are rather drab and cryptic in coloration, although the males of some species exhibit impressive spawning coloration.The genus Etheostoma is diverse in the shape and the coloration of its representatives. The bodies and fins of many of these darters are painted with shades of red, blue, yellow, green, and orange interspersed with black blotches. Members of the genus Ammocrypta are dull and sandcolored. This camouflages them from predators in the large, sand-bottomed rivers they inhabit.
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Darters can reach a length of 12 inches (Percina lenticula, the freckled darter), although most are only a few inches long, even as adults. The smallest is the fountain darter (Etheostoma fonticola), which reaches an adult size of only 1.5 inches. The darter has two dorsal fins, the front with hard spines and the rear with soft rays. The caudal fin is usually rounded or emarginate.
Many darters are sexually dimorphic, and the males are usually larger and brightly colored. Males also develop thickened body tissues, fleshy knobs on the dorsal fin rays and spines, and breeding tubercles during spawning. The showy appearance of courting males is thought to attract females during spawning and accounts for the large amount of angling interest in this group.
Life history/Behavior
As a group, darters are well adapted to life in fast water and on the stream bottom. Their rounded bodies and slightly flattened head regions are especially hydrodynamic. In addition, most members of the group have completely absent, or poorly developed, swim bladders.They use their enlarged pectoral fins to perch on rocks, allowing them to remain on the stream bottom, out of the current. Their body style is suited to the unique swimming manner for which this group as a whole is named. Darters do not swim in the same way that most fish do; instead, they leap from one spot to another with short jumps or “darts.”
Darters display much variability in reproductive strategies. Most produce few, relatively large eggs and provide some degree of parental care. Most members of the genus Etheostoma are cavity spawners and lay adhesive eggs on the undersides of medium-size rocks, usually in fast water. Males of this genus are often brightly colored to attract females to nest sites that they have prepared for egg laying.
Members of the genera Percina and Ammocrypta spawn in a simpler manner. Two or more individuals group together in fast-water areas over sand between larger rocks. Males and females align their bodies next to each other, then simultaneously release sperm and eggs into the substrate and bury them. This protects the eggs from predation and floods.
Most darters spawn in the spring to early summer. Several species are believed to spawn multiple times per year. Darters are not a long-lived group. Most species live less than 5 years. Sexual maturity is usually attained at between 1 and 3 years.
Food and feeding habits
Darters primarily feed on bottom-dwelling organisms, mostly small insects, worms, and snails. However, as a group they exhibit a diversity of feeding strategies that corresponds to morphological differences. Large darters feed on insects on top of rocks or pick them out of sand and gravel.Shorter, more flexible darters often feed on clinging insects between and underneath rocks. As a result of these different feeding strategies, several darter species can coexist in the same area of a stream.
Distribution
Darters range from northern Mexico into Canada and from the eastern coastal plains west to the Continental Divide. Only one species, the Mexican darter (Etheostoma pottsi), occurs west of the Continental Divide, in northern Mexico.Darters are most diverse in the southern Appalachian Mountains of Tennessee and Virginia and in the Ozark plateau of northern Arkansas. The johnny darter (Etheostoma nigrum) is the most widely distributed, followed by the orange-throat darter (Etheostoma spectabile) and perhaps the logperch darter (Percina caprodes).
