Meeting Abstract

35.2  Thursday, Jan. 5  Novel remote sensing technique assesses intertidal habitat and reveals population expansion of West Indian Topshell MEYER, Erin L*; MATZKE, Nicholas J; WILLIAMS, Simon; Univ. of California, Berkeley; Univ. of California, Berkeley; Univ. of California, Berkeley emeyer@berkeley.edu

Habitat assessments are important for conservation because they establish baselines for spatial distribution and preferred habitat of target species. These data are useful for testing species recovery and for predicting future population expansion. Current methods for mapping intertidal habitat require detailed field data, which are often unavailable and laborious to collect. Thus, developing alternative methods is crucial for exploited species, such as Cittarium pica. Fishing pressure on C. pica recently increased, resulting in the establishment of management plans in six island territories. In Bermuda, C. pica was fished to extinction in the 1800s and was reintroduced in 1982. To monitor recovery in Bermuda, we used a novel remote sensing technique to correlate habitat and species distributions while estimating population size and density. Starting with a digital aerial photograph, we outlined the coastline and manually classified it into three categories: rock, vegetation, or beach. Using these high-resolution data as a training dataset, we created a supervised classification system for identifying intertidal habitats in lower resolution Landsat images. The coastline consists of 74% rock and shore-hardening structures, 10% beach, and 16% vegetation. On the habitat map produced with these techniques, we mapped C. pica distribution and population sizes for five field localities in Bermuda. Results demonstrate that C. pica population has increased since the 2003 island-wide survey indicating that the species is continuing to recover. We also used these data to predict future expansion of C. pica into unoccupied habitat. This is the first habitat assessment for C. pica, and the methods developed herein will be applied throughout the Neotropical Western Atlantic.