Median (solid line), mean (white square), inner quartile and range (box and whiskers) and any outliers to the range (bold filled circles) showing all raw data for flat oyster dredge efficiency by ground type (hard sediments, mid = mix of hard and soft areas) for uniformly or even distributed oysters in the September session only. Despite appearance of trend towards reduced efficiency moving from hard to mixed ground – this is not a significant difference and matches the result from April (Fig. 3).