Term of Award

Fall 2008

Degree Name

Master of Science in Biology (M.S.)

Document Type and Release Option

Thesis (open access)

Department

Department of Biology

Committee Chair

Sophie S. George

Committee Member 1

C. Ray Chandler

Committee Member 2

Bruce Schulte

Committee Member 3

Sophie S. George

Abstract

Quantifying the density of burrowing crabs is challenging, and several techniques have been developed to accomplish it, including burrow counting, visual surveys of surface-active crabs, and substrate excavation. These techniques have been compared in mangrove forests but not in a salt marsh, nor has anyone attempted to excavate traps repeatedly for multiple days. Previous comparisons have not examined these techniques over the course of several months, nor considered the cost and precision associated with each technique. Therefore, from May of 2007 to April 2008, I conducted burrow, visual, single excavation, and repeated excavation surveys to estimate Uca pugnax density in a salt marsh on Tybee Island, Georgia and estimated the cost and precision associated with each technique. Only single and repeated excavation accurately measured juvenile density, but these methods were more costly and caused temporary habitat damage. Burrow surveys yielded reliable adult density but visual surveys underestimated adult and juvenile density, likely due to the difficulty of spotting small crabs in thick vegetation. This information may be useful to management officials monitoring fiddler crab populations and their predators in salt marsh ecosystems.

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