Browsing by Author "Bellgraph, Brian Joseph"

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Competition potential between sauger and walleye in non-native sympatry : historical trends and resource overlap in the middle Missouri river, Montana
(Montana State University - Bozeman, College of Letters & Science, 2006) Bellgraph, Brian Joseph; Chairperson, Graduate Committee: Christopher S. Guy
Sauger Sander canadensis populations throughout Montana and North America have exhibited declines over the past few decades. Sauger population abundance declined in the middle Missouri and Yellowstone rivers of Montana in the mid-1980s following a period of drought. Higher flows resulted in a rebound of the lower Yellowstone River population; however, the middle Missouri River population has remained at low abundance. Various factors may contribute to the reduced population abundance of sauger in the middle Missouri River, including interspecific competition with walleye Sander vitreus. Historical trend data of sauger and walleye were assessed to determine long-term trends of sauger and walleye fitness. To assess competition potential, seasonal migrations, habitat use, and diets of both species were compared in the middle Missouri River. Trophic position of sauger was also compared between the middle Missouri and Yellowstone rivers to evaluate the trophic status of sauger in sympatry and allopatry with walleye. Sauger and walleye were tracked using radio telemetry to establish and compare seasonal migrations. Habitat use was compared at three hierarchical scales, diets were collected on fish sampled using electrofishing, and diet overlap was calculated.