Estimated number of dredge tows required to detect changes in oyster abundance in Galveston Bay

The number of collections at different sites and replications at each site necessary to detect most changes in oyster abundance in the Galveston Bay system and at a single site therein were estimated using variances measured during December 1984 at 14 sites. Changes of greater than or equal to 50% in total oyster abundance within the system could be detected with one tow at seven different, randomly selected sites. To detect similar changes in each of market (greater than or equal to 76mm), small (25-75 mm) or spat (less than 25 mm) oysters, 20 sites would have to be sampled. Ten to thirty-four replicate tows would be needed to detect 50% changes in each category at site. At least 55 sites should be sampled using one tow per site to maximize the probability of collected data from as many reefs in the system as possible within present (1986) budgetary constraints.