About Lythrurus umbratilis (Girard, 1856)
The average adult redfin shiner, Lythrurus umbratilis, reaches 3.5 inches (8.9 cm) in length. This species is easily recognizable by its deeply compressed body, large eyes, and distinct coloration. Its body is light olive, with a dark stripe running along its spine. Sides are typically very silvery, and breeding males develop a reddish tint. The redfin shiner is native to the Great Lakes and their tributaries, the Mississippi River Basin, and ranges south through the Ohio and Mississippi River basins, extending west to Texas. While these river systems form the species' overall geographic range, its specific distribution within individual streams remains largely unknown. Redfin shiners are most common in small- to medium-sized streams across a variety of ecological settings. They can be found from slow-moving bays to high-gradient upland streams, and are generally classified as pool dwellers. They are most likely to occur in streams within their range that contain large, slow-moving pools, which act as their microhabitat where they spend most of their lives. They prefer pools with a temperature near 20 °C (68 °F) and neutral pH, and favor calm water in low-gradient streams over sand or gravel substrates that have some vegetation. Though they prefer calm, slow-moving pools, they can tolerate some faster-moving water. The redfin shiner is a surface feeder. It primarily preys on aquatic and terrestrial insects and other small invertebrates, but also feeds extensively on algae. It is not a specialized feeder, and consumes mostly whatever food is available. The species has many competitors it must outcompete for resources including food and spawning grounds. It competes most directly for food with other members of the genus Lythrurus, as well as many other cypriniform species. In addition to competitors, the redfin shiner has a wide range of predators. Almost any piscivorous fish with a jaw gape large enough to accommodate a 3.5-inch redfin shiner will prey on this species. Redfin shiners are ecologically important as a major part of the diet of many game fish in the eastern United States. Other predators include any mammals, reptiles, and birds that feed on small fish within the redfin shiner's range.
