Benthic Habitats and the Effects of Fishing

Symposium Abstract: The Use of Field Calibrated Side-Scan Acoustic Reflectance Patterns to Quantify and Track Alterations to Benthic Habitat Associated with Louisiana’s Oyster Industry

C. Wilson, H. Roberts, Y. Allen, and J. Supan

doi: https://doi.org/10.47886/9781888569605.ch35

Coastal Louisiana, like many deltaic land masses, faces continued landscape alteration from natural processes and anthropogenic impacts that affect estuarine habitat. The most promising steps to slow/ mitigate these changes are river diversions that introduce freshwater and sediment to river-flanking environments and to help establish ideal salinities over historic oyster grounds. Critical to the success of these programs is a rapid and accurate means to qualify and quantify changes in oyster habitat. Digital high-resolution acoustic instrumentation linked to modern data acquisition and processing software was used to build baseline of information for evaluating future changes in shallow water bottoms, with special emphasis on oyster habitats. Application of digital side-scan sonar (100 and 500 kHz), a broad-spectrum sub-bottom profiler (4-24 kHz) for rapidly acquiring water column, surficial and shallow subsurface was used to map over 10,000 ha of water bottom. Geo-referenced side scan sonar mosaics were incorporated into a GIS data base. These data sets, “calibrated” with surface sampling, coring, and other “ground truthing” have established that numerically indexed acoustic reflectance intensities correlate closely with surface shell and oyster reef density. With image processing techniques to analyze mosaic reflectance patterns, we estimated the percent and total acreage of several bottom types.