Status and trends analysis of oyster reef habitat in Galveston Bay, Texas

A new technique was utilized to determine the status and trends of oysters (Crassostrea virginica) populations in Galveston Bay, Texas. An acoustic profiler was used to differentiate substrate type, a fathometer to assess bottom relief and a global positioning system to accurately establish position. Sediment characteristics and reefal features were interpreted from the acoustic profiler chart record according to the amount of return generated. We were able to distinguish oyster reef from mud, sand and shell hash. Occasional ground-truthing was required to distinguish reef from clam beds and coarse shell hash. The bathymetry, sediment type and geographic position data were computerized and processed for use by a Geographic Information System (GIS) to produce the maps. We used Arc/Info software to produce maps covering the majority of Galveston Bay, Trinity Bay, East Bay, and West Bay. Reefal area was compared to that determine in the late '60s and early '70s by the Texas Parks and Wildlife Department. The amount of oyster reef and oyster bottom recorded in this study is substantially higher than that depicted on the TPWD charts. Differences can be attributed to our improved methodology and new reef formation in the 20 yr since the TPWD study was completed. The oyster reefs of Galveston Bay can be divided into naturally occurring reef and reef that has originated through man's influence. In many areas of the bay, reefs originated through man's influence (e.g. spoil banks, oil and gas field development, oyster leases, modifications in current flow) account for 80 to 100% of the entire reefal area