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School of Environment and Natural Resources


Chris Johnson's Graduate Defense Seminar

Jul 25, 2016, 9:00am - 10:00am
128 Heffner Wetland Research and Education Bldg.

Chris Johnson, MS Candidate in Fisheries and Wildlife Science, will present Direct and Indirect Effects of the Invasive Orconectes rusticus on Native O. sanbornii in Ohio Streams as his Graduate Defense Seminar in 128 Heffner Wetland Research and Education Bldg.

While the direct effects of non-native species as predators and competitors have been widely studied, the indirect effects of invasive species as novel prey has been less explored. Novel prey may supplement native predators, positively influencing predator abundances, resulting in concomitant effects upon native prey. In Ohio, the invasive rusty crayfish, Orconectes rusticus, has been implicated in the decline of native Sanborn’s crayfish, O. sanbornii.  This research aimed to evaluate the indirect effects of O. rusticus on O. sanbornii in Ohio streams. I used a combination of field observations and experimental manipulations to compare population demographics and predation risk of native O. sanbornii and O. rusticus within invaded and non-invaded streams. Further, I compared the behavioral responses of O. sanbornii and O. rusticus to varied risk of predation, a heterospecific versus conspecific competitor, and the interaction between predation risk and competitor identity. Results suggest that size plays a central role in the ability for O. rusticus to successfully invade. Further, native O. sanbornii suffers a trade-off between managing risk of predation versus costs of competing with a novel competitor.  However, invasive O. rusticus responds to competition from O. sanbornii in ways which are advantageous in risky environments, suggesting there are key behavioral mechanisms by which novel prey may indirectly impact native prey through the interacting forces of predation risk and competition.