Atlantic oyster drill abundance per quadrat based on 693 total quadrat samples at eight study sites in Richardson Bay, CA, surveyed quarterly from June 2017 to July 2018. The order of the sites from left to right corresponds to clockwise around Richardson Bay from southwest (Dunphy Park), to northeast (Hilarita Ave.). Surveys were not conducted in deep mud flats, which is represented by the absence of data in some instances. The horizontal lines at Dunphy Park, Bothin Marsh, Brickyard Park, and Strawberry Point represent zeroes; drills were never observed at these sites. One extreme outlier at Cove Apartments (74.3 drills per 0.25 m2, third quarter of 2017) has been removed to present the data more clearly.