Cumulative mortality curves for each of the units in a group. Data are % cumulative mortality. A Eight units being the segments in a cultivation tray (Group 17); synchronous onset of mortality among units; n = 40 oysters per unit. B Twelve units being the baskets on a long-line (Group 13); asynchronous onset of mortality among units; n = 92 oysters per unit. In both A and B there is incomplete mortality in each unit and variable final mortality rates between units.