Title page for ETD etd-06132005-163156

Type of Document Master's Thesis
Author Fisher, Jonathan C.
URN etd-06132005-163156
Title Do Predator Exclusion, Position, and Plant Architecture Influence Hydrilla-Dwelling Macroinvertebrate Communities?
Degree Master of Science (M.S.)
Department Renewable Natural Resources
Advisory Committee
Advisor Name Title
William E. Kelso Committee Chair
D. Allen Rutherford Committee Member
James P. Geaghan Committee Member
  • macroinvertebrates
  • hydrilla
  • plant architecture
  • predation
  • fish diets
Date of Defense 2005-05-18
Availability unrestricted
Hydrilla verticillata invaded south central Louisiana during the 1970s subsequently becoming the dominant submerged macrophyte in floodplain habitats of the Atchafalaya River Basin. The effects of hydrilla on littoral habitat structure, water quality, fish, and macroinvertebrates have been pervasive, and I hypothesized that dense hydrilla stands would also impact vertebrate predation on resident macroinvertebrates, although predation effects would likely be mediated by bed position. During 2003 and 2004, I conducted exclosure experiments in the Atchafalaya River Basin with artificial substrates to test for variations in hydrilla bed macroinvertebrate communities caused by predation, plant architecture, and bed position. To determine invertebrates consumed by fishes, I also examined stomach contents of potentially invertivorous fishes inhabiting these beds. Results indicate that position and predation are important in structuring macroinvertebrate communities, whereas plant architecture had little effect. My diet analyses indicate that the fishes sampled fall into three categories: 1) those that do not feed on macroinvertebrates; 2) those that feed on small invertebrates (e.g., dipterans); and 3) those that feed on large invertebrates (e.g., decapods) and poeciliid fishes. Further, the diets of the invertivorous fishes coincide with the distributions found in the macroinvertebrate community and, in general, those macroinvertebrates most commonly found in fish diets occurred in greater densities within the bed interior.
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