Fundulus sciadicus Cope, 1865
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Basis for Listing
The plains topminnow has both declined and been extirpated from portions of its North American range. In Minnesota, it is restricted to the Rock River system in small prairie streams that are tributary to the Missouri River in Pipestone, Nobles, and Rock counties. The species has specialized habiitat requirements, and its fragile habitat is subject to siltation and drought. Given its extreme rarity in the state, the plains topminnow was listed as a special concern species in Minnesota in 1984.
The plains topminnow is olive-brown in color on its back and sides, white below, and reaches a total length of 4-6.5 cm (1.6-2.6 in.). Its stout body has 34-36 scale rows and lacks the black bars that are characteristic of the more common banded killifish (Fundulus diaphanus). It has a small mouth with a projecting lower jaw, a broad head, and a single, soft dorsal fin, with 8-10 rays, that lies slightly behind the front of the anal fin. Male plains topminnows have larger anal fins than females, red fin edges, blue speckles, and a gold stripe down their back.
Plains topminnows are found in spring-fed pools and backwaters of clear to moderately turbid creeks and rivers that have a sand or rock bottom and a heavy growth of aquatic plants (Hatch et al. in preparation).
Biology / Life History
Little is known about the life history of the plains topminnow. It lives singly or in small schools near the surface of the water (Pflieger 1975). Females deposit eggs on aquatic plants, and the eggs hatch in 8-20 days. Predators likely include larger fish such as bass (Micropterus spp.) as well as fish-eating birds.
Conservation / Management
The plains topminnow is one of the rarest inhabitants of Minnesota's southwestern prairie streams (Hatch et al. 2003). Water quality and quantity of streams in southwestern Minnesota should be maintained at present levels and efforts to minimize siltation should be encouraged. Research about this species' natural history is needed to support management and conservation.
Conservation Efforts in Minnesota
Fish surveys in the 1990s and 2000s increased the known number of locations of this species in Minnesota to at least 20 and the known number of rivers and tributaries to eight, all of which are within the Rock River system. The plains topminnow continues to be a target species for the Minnesota Biological Survey. Additional research needs for the species in Minnesota include life history studies, genetic analysis, identification of habitat guilds, and the determination of specific habitat impacts and stressors.