Survey of the Fishes and Habitat in the Upper Moreau River, Perkins County, South Dakota

The goal of this study was to document the fishes and habitat characteristics in the upper Moreau River, Perkins Country, South Dakota. Presently, the status of several species, including western silvery minnows, plains minnows, and flathead chubs, is in question within the Missouri River basin of the USA and Canada. My primary objectives were to (1) compare species richness and composition data to data collected in 1955, and (2) document the habitat for comparison to concurrent and future studies in western South Dakota. Secondary objectives included (I) a meristic and morphometric comparison of the western silvery minnow and plains minnow, and (2) an assessment of their status within the Missouri River basin in 1995 and 1996. 19 species were collected from the Moreau River. New species records for the river were common carp, emerald shiner, white bass, black crappie, and largemouth bass. Of these, white bass, black crappie, and largemouth bass comprised 0.06% of the total catch in 1995 and were considered incidental species. Yellow perch was historically collected, but was not found during this study. Excluding incidental species, the species richness and composition was similar between historic and current survey periods. Landuse in the Moreau River basin was dominated by livestock grazing and ranching. The majority of bed substrates were fines at all stations and, of these, silt and sand were the most common. More than 75% of all transects were classified as runs during both years. In 1995, 45% of transects were proximate to pasture and 16% were highly grazed. Eighteen percent of transects were pasture in 1996 and none were highly grazed. Banks were primarily vegetated with sedges Carrex spp. and rushes Juncus spp. and less than 50% were classified as unstable either year. Western silvery minnows, plains minnows, and flathead chubs were found throughout the river and ranged from 10 - 19% of the total catch. In 1996, these species were delisted in South Dakota. Identification of Hybognathus spp. relies on necropsy and examination of the basioccipital process. However, we correctly identified over 90% of our specimens using external differences in their eye diameter, pupil diameter, and number and size of scale rows across the belly. A stepwise discriminant function analysis correctly classified 88% of the minnows using differences in the number of scale rows (81 %), pupil diameter (4%), nasal diameter (2%), and eye diameter (2%). In the Missouri River, populations of western silvery minnows and plains minnows have declined from North Dakota to Missouri, while populations in other basins have declined in Wyoming, Colorado, North Dakota, Nebraska, Kansas, Iowa, and Missouri. Populations in tributaries to the Missouri River were considered stable in. Montana and South Dakota. Furthermore, biologists have suggested that populations in Iowa, Nebraska, Kansas, and Missouri may no longer be sympatric, and these species may have hybridized as a result of habitat alterations. The taxonomic dichotomy and distinct external differences of western silvery and plains minnows are another indicator that habitat conditions in the Moreau River have remained relatively unaltered