Comparison of oyster populations sampled by dredge and quadrat at different locations within four Texas estuaries from 2018-07-02 to 2018-10-03

Dredge efficiency comparisons were conducted at 19 locations within four Texas estuaries (Mission-Aransas, Guadalupe, Lavaca-Colorado, San Jacinto) from 2018-07-02 to 2018-10-03. The locations encompassed a range of environmental conditions and oyster densities within and among estuaries. Oysters were sampled in triplicate using quadrat samples taken by scuba divers (0.5-m2), and then dredge tows (14.625 m2: 0.375-m wide dredge for 30 s at 1.3 m s-1) at each location. The proportion of mud, sand, shell hash and whole shell in each quadrat sample was estimated before the top 10 cm of each quadrat was excavated for oyster shells. The abundance and volume of live and dead oysters (>25 mm) were standardized to unit area, and all live oyster heights were measured (+/- 1 mm) in each sample. Shell volumes were determined by water displacement in a measuring bucket. Ancillary salinity and depth data were measured with a YSI ProDSS sonde at each location.