Wednesday, May 28, 2008 - 9:45 AM
386

Effects of fishes on the functional make-up of an adult aquatic insect community

Jeff Wesner, Department of Zoology, University of Oklahoma, 730 Van Vleet Oval, Room 314, Norman, OK 73019

Insects emerging from aquatic habitats form an important component of riparian food webs, subsidizing several riparian consumers.  Fish predation on immature aquatic insects can alter properties of the emergent insect community and alter the flow of organisms across the aquatic-terrestrial boundary.  The focus of previous research treats aquatic-terrestrial insect subsidies largely in terms of biomass or abundance.  While important, this approach ignores potentially important variation in the life-histories and behaviors of organisms that comprise the subsidy.  In addition, fishes with different feeding strategies may have different effects on emerging aquatic insects.  In this study, I categorized the adult stages of emergent aquatic insects into two broad classes based on their adult feeding role: consumers (e.g. dragonflies) and non-consumers (e.g. midges).  Using large outdoor stream mesocosms, I tested whether two fish species with different feeding strategies, a water-column insectivore and benthic insectivore, altered the proportion of consumers in the emergent insect community.  Both fish species significantly decreased the number of emerged consumers (mostly dragonflies), but not non-consumers (mostly midges), compared to a fishless control.  For the benthic insectivore treatment, this resulted in a significant reduction in the proportion of consumers in the emergent insect community.  Potential mechanisms will also be discussed.


Web Page: Ecology, Fishes, Aquatic-Terrestrial Linkages