Gauging the Threat of Predation on the Topeka Shiner (Notropis topeka) in Minnesota: Final Report

The Topeka shiner (Notropis topeka) is a small, stout minnow that inhabits slow-flowing habitats of headwater streams in the central prairie regions of the United States (Tabor 1998). In Minnesota, this species exists only in the Missouri River drainage, located in the southwestern corner of the state (Phillips et al. 1982). Topeka shiners have relatively stable populations in Minnesota (Dahle 2001); however, their distribution and abundance have greatly declined over most of their range during this century, leading to their listing as federally endangered (Tabor 1998). Although habitat destruction and degradation are thought to be the primary causes for this decline (Tabor 1998), predation by introduced piscivorous species (particularly largemouth bass, Micropterus salmoides), following the construction of impoundments in streams containing Topeka shiners, has also been implicated (Prophet et al. 1981, Layher 1993, Schrank et al. 2001). There have been no studies on the impacts of predation on the Topeka shiner, thus the significance of this threat is currently unknown (Tabor 1998). The purpose of this study was to determine which syntopic fishes prey on Topeka shiners in Minnesota and to gauge the impact of such predation by means of predator gut content analysis.