Comparison and conversion of hydraulic patent tong and diver quadrat oyster sampling data on degraded and restored oyster reefs

Abstract Objective The objectives of this study are to (1) quantitatively compare density estimates of oysters (family Ostreidae) from diver quadrats and hydraulic patent tongs to determine if the gear types produce comparable oyster density estimates, (2) determine if habitat type (i.e., restored versus degraded reef structure) impacts the comparability of oyster density data from each sampling type, and (3) create a conversion factor that can be used to calibrate oyster density estimates between the two gears so that the results can be comparable. Methods Because oyster reef degradation likely impacts the efficiency of sampling gear, we stratified our sampling efforts by habitat type (e.g., restored versus degraded reef structure). A total of 10 reef sites were selected in Galveston Bay, five of which were designated “degraded” and five of which were designated “restored.” At each reef location, patent tong and diver quadrat samples were collected and the density of live oysters (>25 mm), dead oyster shell (26–50 mm and >50 mm), and shell height of live oysters were recorded. Results We observed differences in densities between gear types and habitat types for live oyster and shell, though no significant interaction was detected between gear and habitat type. Linear regression relationships were developed for live oyster and shell density to aid in conversion of data between gear types; however, high variability among samples may hinder predictive performance of gear conversions. Regardless, hydraulic patent tongs ranged from approximately 43% to 73% efficient compared with quadrats depending on reef component (i.e., live oysters, small shell, or large shell). Conclusions These findings could aid oyster monitoring and restoration efforts globally by allowing for the comparison of monitoring data collected with these different gears and by decreasing personnel risk and labor hours associated with diver quadrat sampling.