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Graduate Student Defense Announced

By: Kathleen Tuck   Published 10:21 am / September 29, 2011

The campus community is invited to sit in as graduate students defend their theses and dissertations. Barry Bean is scheduled on Wednesday, Oct. 5.

Student: Barry Bean
When: 12:40 p.m., Wednesday, Oct. 5
Where: Multipurpose Classroom Building, Room 118
Title: “Spatial Distribution and Habitat Use of the Bliss Rapids Snail”
Advisor: Matt Dare
Program: Master of Science in Biology

Abstract: I conducted a three-year field study of the Bliss Rapids snail, Taylorconcha serpenticola, a threatened aquatic mollusk endemic to the Snake River drainage. The objectives of my study were to: 1) define the species’ distribution and dispersion, 2) characterize the habitat used by snails, and 3) evaluate abundance monitoring methods. Overall, Bliss Rapids snails were present on 5-13 percent of the cobbles I sampled; however, the species exhibited a contagious (clumped) dispersion pattern within the river. Snail abundance was positively correlated with bed shear stress, and negatively correlated with distance from the nearest upstream rapid and with bank slope. The species was more abundant in north-facing aspects of the river and in deeper water (0.5-1.5 m versus 0-0.5 m). I used a bootstrap simulation to determine the probability of ‘not detecting’ the species when occurrence rates were set realistically low. With occurrence rate set at 0.025, the simulation determined that increasing sample sizes from 40 to 100 cobbles would reduce the probability of not detecting the species from 0.39 to 0.08. Finally, a Monte Carlo simulation-based power analysis was used to determine the sample size needed to detect 10-50 percent declines in Bliss Rapids snail abundance over a five-year period. Results suggest that such declines could be detected with statistical power of 0.8. For the purposes of snail conservation and management, I recommend a sampling protocol sensitive enough to detect a 25 percent decline in abundance over a five-year period. Based on my analyses, such an approach would require sampling 6,000 cobbles annually.


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