Identification of Potential Atlantic Sturgeon Spawning Grounds in the Ogeechee River, Georgia Using Low Cost Side Scan Sonar

Knowledge of spawning habitat for imperiled Atlantic sturgeon (Acipenser oxyrinchus oxyrinchus) is vital to the management and conservation of this once common species. Recent introduction of recreational multi-beam and side-scan sonar equipment allows rapid, low cost acquisition of bathymetric data and substrate imagery in navigable streams. The objective of this study was to use inexpensive recreational-grade side scan and bathymetric sonar to survey the Ogeechee River, and identify potential spawning grounds based on substrate characteristics known to affect sturgeon spawning. In the spring of 2009, we collected sonar data for 288 km of the Ogeechee River. We used DrDepth sea bottom mapping software to georeference side scan images and ARCGIS software to hand digitize patches of suitable spawning substrates. We identified eight reaches, totaling 50,892 square meters, containing potentially suitable substrates and depths. Of these sites, four reaches were subject to anthropogenic disturbance that may render them unfit as spawning grounds. The remaining reaches, totaling 23,538 square meters had a high potential for use as spawning grounds. While confirmation of spawning use by Atlantic sturgeon can only come through direct sampling, this method offers a rapid and low coast approach to identify potential sampling sites.