The trout-perch belongs to the family Percopsidae, which includes only one genus—Percopsis—with only two species. The fish is found only in the fresh waters of North America. One species (Percopsis omiscomaycus) is found mainly on the eastern side; the other species, the sandroller (P. transmontana), is native to the west in the regions around the Columbia River Basin.
Both species are small, with the eastern species averaging 3-5 in (7.6-12.7 cm) in length, with a few reaching 8 in (20.3 cm). The sandroller is a bit smaller.
As the name implies, the trout-perch has characteristics of both the trout and the perch. Like the trout, it has an adipose fin-a fatty fin which projects between the dorsal and caudal fins. It also has a lateral line (a row of sensory pores on its sides) and ctenoid scales (fish scales that have a comb-like projection at their margin).
The trout-perch appears to prefer deep water but may enter shallow water in spring to spawn. It may spawn on sandbars in lakes or up rivers, selecting bottoms of sand or gravel. It appears to be sensitive to rises in temperature, and, in some lakes, a considerable number of these fish die off in the summer as the water temperature rises.
Trout-perches are an important source of food for larger fishes.