Between the mid 1980s and early 1990s, the feeding activity of unusually high densities of the corallivorous gastropod Drupella cornus resulted in massive coral damage along at least 100 km of Ningaloo Marine Park (NMP), with coral mortality approaching 100% at some areas. To date, the density of D. cornus, the area and severity of associated coral damage and longevity of the outbreak itself that occurred at NMP during this event was on a greater scale than recorded on other reefs elsewhere in the world.
As coral communities are a key performance indicator of management of NMP and the Muiron Islands Marine Management Area (MIMMA) it is essential to keep a watching brief on spatial and temporal changes to Drupella densities and cover of associated corals in these conservation reserves. Adhering to this management need, the aim of the Ningaloo Marine Park Drupella Long-term Monitoring Program (NMPDMP), lead by the Department of Environment and Conservation, is to monitor long-term changes to the density of Drupella sp. and cover of associated coral communities at the NMP and the MIMMA. Monitoring of Drupella at NMP has resulted in a data set describing the status of Drupella populations and coral communities dating back to 1987. Between 1987 and 2006, the direction and amplitude of change in Drupella density and percent cover of live hard coral has varied considerably between locations.
Overall however, relative to the outbreak densities recorded during the late 1980s and early 1990s, D. cornus densities have been low to moderate and have not greatly affected coral cover at the NMP and MIMMA. Survey data indicate that the current Drupella population represents no immediate threat to the coral communities at NMP or MIMMA.
