Photo courtesy of Konrad Schmidt
Plains topminnow - Common name
Fundulus sciadicus - Scientific name
Family - Fundulidae - (topminnows)
Status : S3, G4
IDENTIFICATION: The plains topminnow has a yellow-brown to blue-green color in eastern South Dakota. It can grow up to three inches in length (75 mm). It has an upward protruding jaw. Its tail is rounded without a fork. The plains topminnow can be identified in the water quite easily. It often swims on the water surface and can be identified from other fishes in that its tail motion while swimming is similar to that of a tadpole. The tail fin is a deep red color in the mid to late summer months and is easily distinguishable at the water surface.
SIMILAR SPECIES FOUND IN SOUTH DAKOTA: The central mudminnow and banded killifish are similar species found in eastern South Dakota. The central mudminnow is a darker color (olive-brown to brownish-black) and does not have an upward protruding lower jaw. The banded killifish has vertical stripes along its side.
HABITS AND HABITAT: The plains topminnow is typically found in pools and backwaters of quiet creeks and small to medium sized rivers, usually near vegetation. It spawns in the summer and deposits eggs on aquatic vegetation. The male's fins turn red during breeding.
DISTRIBUTION: Distribution Map The plains topminnow has a limited range within the Missouri River Drainage, from eastern Wyoming to southwestern Minnesota and northwestern Iowa. There are two isolated populations within its range that occur in the south in central Missouri and where the Missouri, Kansas and Oklahoma borders meet. The plains topminnow occurs in the James, Vermillion and Big Sioux River Basins in eastern South Dakota. It is most common in the James River Basin where it occurs in several tributaries as well as backwater pools and ponds; even in dugouts. Counties where the plains topminnow has been found include: Sanborn, Hanson, Hutchinson, Bon Homme, and Yankton in the James River Basin; Clay County in the Vermillion River Basin; and Minnehaha and Lincoln Counties in the Big Sioux River Basin.
CAUSES OF CONCERN AND CONSERVATION MEASURES: The plains topminnow has a limited range in which eastern South Dakota forms the upper western edge. The plains topminnow is threatened by any activity causing alteration of its habitat, particularly groundwater withdrawal and drainage of wetlands.