The brook silverside is commonly collected in pools 9 through l3 of the Mississippi River and is occasionally observed in downstream pools. It also has been collected in the Maquoketa and Cedar rivers. Recent collections in central Iowa rivers have not documented this species. Habitat preference for brook silversides is clear, warm waters having little current.

Brook silverside is a very slender, elongate and translucent fish. The head is flattened with a beak-like snout and a lower jaw that slightly projects toward the front. Upper and lower jaws have minute, needle like teeth. The long, sickle-shaped anal fin has one spine and 20 to 26 rays. Two dorsal fins are located on the posterior half of the back. The first dorsal has 4 spines, and the second has one spine and 5 rays. Scales are small and cycloid with 75 to 84 scales along the lateral line. General body color is pale green. The dorsal scales are outlined with black specks, the sides are silvery with a bright silver horizontal stripe, and the belly is silvery white. The fins are plain, except for a spinous dorsal fin and pigmentation near the tip. Adults usually average 2 to 4 inches in length.

Brook silversides seldom venture below the upper three feet of water, and most of their time is spent within inches of the surface. The up-turned mouth and flattened head are adapted to a surface-dwelling life. Young fish forage in open water on cladocera, copepods and other small crustaceans. As they become older, the fish move toward shore and feed on a diet of both aquatic and terrestrial insects. The fish is very active in the daylight and moonlit nights but lies motionless near the surface on dark nights.

Spawning takes place over shallow, gravel bottoms or sites with submerged vegetation, from late May to early August. The eggs are extruded singly as a spawning pair moves at an angle from the surface to the bottom. Each egg has an adhesive filament that attaches to the first item it contacts. At a temperature of 77 degrees F the eggs hatch in about 8 days. The brook silverside matures, spawns and dies by the end of its second summer of life.

The brook silverside is a frequent forage of predatory fish species in waters where they exist.

*Mayhew, J. (editor). 1987. Iowa Fish and Fishing. Iowa Department of Natural Resources, Des Moines, Iowa. 323 pp.