Linking Policy and Ecology in the Management of Aquatic Ecosystems: Stream Restoration and Invasive Species Legislation

Freshwater ecosystems in the midwestern United States are adversely impacted by historical deforestation and by modern incursions of invasive species. While restoration of streams by the addition of large wood is a common management technique designed to increase populations of native fishes, the functions of the current, relatively low volumes of large wood on habitat use by brook trout, stream invertebrate drift, and brook trout diet remain understudied in midwestern streams. Similarly, the effectiveness of federal legislation at protecting freshwater ecosystems from perturbation by invasions of nonindigenous species is also poorly understood. My thesis begins by investigating the role of current volumes of large wood in determining the location and diet of brook trout, and the content of stream drift. I found that although higher volumes of large wood positively affected the biomass of drifting aquatic invertebrates, brook trout abundance did not differ between higher and lower-wood reaches. However, unlike most other studies of brook trout foraging, brook trout in this study did not consistently select for terrestrial invertebrate prey over aquatic invertebrate prey, suggesting that the provision of aquatic prey by large wood benefits foraging brook trout. Abundant, nonindigenous weevils (Curculionidae: Phyllobius oblongus) represented a short-term prey subsidy to brook trout in two of the five study streams, but the overall effect of these nonindigenous weevils on the stream and riparian area remains unknown. Before new nonindigenous species, such as this weevil, are established, opportunities exist to prevent their introduction through legislation. However, the effectiveness of federal legislation at protecting these ecosystems from new invasive species is low. I analyzed the historical effectiveness of the Lacey Act, which has given the U.S. Department of the Interior the power to prevent the importation and interstate transport of invasive species since 1900, but with little impact on actual U.S. invasions.