The Topminnows and Killifishes are typically found near shores of streams, in the backwaters, or in runs of small- to moderate-sized streams. Several species prefer water with dense vegetation. All species of Fundulus have an upturned, terminal mouth, which is an adaptation for feeding at the surface, although the Plains Killifish and Northern Studfish sometimes feed off the bottom. Spawning behavior varies among the species, but none of the Topminnows build nests or provide direct parental protection for the eggs and young. About six of the 25 fishes of this genus occur in the central United States.
The Mosquitofish is an introduced fish in Kansas. It was released here for the purpose of mosquito control. The species is closely related to the “guppy”. However unlike the guppy, the mosquito fish is more tolerant of cool water temperatures. It is the only live bearing breeder in Kansas.