Date of Award

5-2018

Degree Type

Thesis

Degree Name

Departmental Honors

Department

Wildland Resources

Abstract

Previous studies quantifying the density, distribution and diversity of aquatic insects overwhelmingly focus on larval life stages. However, many aquatic insects exhibit selective oviposition behaviors, with a preference for emergent substrates along a river's edge. The practice of hydropeaking creates an artificial intertidal zone that is absent from natural rivers and to which freshwater organisms are not adapted. We hypothesized that this novel disturbance could reduce the availability and temporal persistence of oviposition habitats resulting in egg mortality. To test this hypothesis, we quantified the oviposition behavior of four aquatic insects using a hierarchical field survey of habitat availability and utilization. We found that three out of four genera exhibited preferences for larger, emergent substrates located along the river edge, thus increasing the likelihood of desiccation during stage height fluctuations. When subject to experimental drying, we observed up to 93% egg mortality during desiccation lasting two hours or less, and 100% mortality when desiccation exceeded four hours. These paired field and experimental results suggest that hydropeaking could impart a population bottleneck on aquatic insects. This project is on-going and these writing do not reflect the final views of the authors.

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Faculty Mentor

Scott Miller

Departmental Honors Advisor

Geno Schupp