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The river darter (Percina shumardi) is a benthic species of freshwater fish in the Percidae family (Perches and Darters) of order Perciformes. It is native to a North America. It is an inhabitant of small and medium rivers where it occurs in rocky riffles with clear, fast-flowing water. The river darter can reach up to 7.3cm in length and has an average lifespan of three years. It can be distinguished from other darters by its unique front and rear spots on the dorsal fin. The river darter can reach lengths of 7.3cm

Geographic Distribution
The river darter is a species native only to the United States and Canada. Within Canada, the river darter is native to southern regions including the Hudson Bay basin, Ontario, and Manitoba. Within the United States, the river darter is native to a band that starts northward in Canada and extends into Minnesota and North Dakota and continues to the Gulf drainages in Alabama and Texas. The river darter is the most common species of darter in the Mississippi River Channel.

Description
River darters are olive brown with distinct dorsal saddle shaped blotches of darker coloration and a mottled back. The dorsal saddles form form 8-10 faint bars along the body that become more ovular towards the tail. The dorsal fins are clear with light stippling or banding, while nuptial males have a prominent curved golden band in the posterior part of the spiny dorsal fin. The dorsal fin has 15 rays. The anal fin has 11 rays. Male river darters have greatly enlarged anal fins that are tuberculate when breeding. The head has a moderately pointed snout with a distinctive bar under the eye. They can grow up to 73mm in length- males are larger than females. Recognition: Darters are small fish and are characterized by two dorsal fins. Darters of the genus Percina have dorsal scutes, a line of modified scales on the midline of the breast and belly. They have two anal spines and a complete lateral line. The river darter has small black blotches near the front and rear of the first dorsal fin. It is olive-colored above, with indistinct dorsal saddles. There are eight to fifteen dark lateral bars along the length of the fish. The anal fin is long, reaching well beyond the dorsal fin to the caudal fin in large males. A black spot is present on the caudal fin, and a distinct teardrop mark is present beneath the eye. The river darter reaches a maximum length of three inches (Page 1983, Page and Burr 1991). Males are darker and more distinctly marked during spawning season, but do not develop bright colors like many other darters. Tubercles develop on the caudal, pelvic and anal fins, and occasionally also occur on the head. Similar fish include the channel darter (P. copelandi), which can be distinguished by having horizontally oriented bars along side the body and no elongated anal fins in males, the blackside darter (P. maculata), and the snail darter which has larger blotches and no bars along its side. All of these species lack the front and rear spots characteristic of the river darter dorsal fin.

channel darter has horizontally oriented bars along side and no elongated anal fins in males. saddleback, snail darter(larger blotches and no bars along side) and stargazing

Habitat
As its name implies, the river darter can be found in major rivers and at the mouths of adjoining tributaries. River darters prefer to inhabit regions with moderate to swift currents in regions around 1 meter deep. They inhabit chutes of oxbow rivers and riffles with sand, gravel, and rocky substrates. During the evening river darters migrate inshore and are commonly found along sandbars at depths of .6-.9s. During the day they are most abundant in 1.2 meters or more of water.

Response to Turbidity
The river darter relies on frictional contact with the substratum to maintain its position while minimizing its energy usage. The river darter’s enlarged pectoral fins help create negative lift and increase friction to counteract turbidity. As current speed increases, the river darter, like many lotic fishes, increases its frictional contact with the substratum by releasing gasses from its swim bladder, which increases its density.

Management
The abundance of the River darter in the Mississippi River and tributaries indicates that it is not extremely sensitive to turbidity and water pollution. However, the river darter does require deep swift water habitats, which are quickly disappearing with flood control and river impoundment projects. In order to protect the river darter, rivers need to be restored and maintained in their natural state with intact flow regimes. The river darter is best surveyed in the summer, when water levels are typically at their lowest.

Diet
The river darter is an invertivore that primarily feeds during the day. . Adult individuals feed on a wide variety of all aquatic invertebrates such as midge and caddisfly larvae, which are common in streams and rivers. Snails are another fundamental aspect of the diet of mature river darters. chironomids, trichopteras, and small crustaceans. Juvenile river darters primarily feed on small zooplankton floating in the water.

Lifecycle
The river darter attains much of its adult size during the first year of development, and reaches sexual maturity by the age of one. Males tend to develop faster and become larger than females. The average lifespan of a river darter is between 3-4 years. Individuals reach sexual maturity after around one year.

River darters are brood hiders; they do not guard their eggs. After they have laid their eggs they do not provide parental care. Females bury their fertilized eggs in gravel depressions in areas of slow current. These gravel depressions are called redds. River darter eggs are able to tolerate temperatures between 13-26* Celsius. Some reports indicate upstream migration of river darters during the spring. After spawning the fish may move downstream to reach overwintering habitats.

number of reports of upstream migration to spawn in spring and downstream movement in fall to reach overwintering habitats (Cross 1967; Trautman 1957). In Arkanasas, during evening and night, migrates inshore and is commonly found at depths of .6-.9 m along sandbars; during the day, most abundant in 1.2 m or more water (Robison and Buchanan 1988). Sanders and Yoder (1989) note species movement into shallow water after sunset.

Etymology
The river darter's scientific name comes from the Greek root word Percina or 'little perch' and the word shumardi which was given in honor of its discoverer, Dr. G.C. Shimmered, a surgeon with the United States Pacific Railroad Survey.