High peak settlement of Diadema antillarum on different artificial collectors in the Eastern Caribbean

The massive die-off of the herbivorous sea urchin Diadema antillarum in 1983 and 1984 resulted phase shifts on Caribbean coral reefs, where macroalgae replaced as most dominant benthic group. Since then, D. recovery has been slow to non-existent reefs. Studying settlement rates can provide insight into mechanisms constraining antillarum, while efficient collectors be used identify locations with high collect settlers for restoration practices. aim this study was compare pre post determine possible peaks Eastern island St. Eustatius. Additionally, we aimed effectiveness reproducibility five different antillarum. around Eustatius highest May, June August low during rest study. Before die-off, recorded Curaçao throughout year characterized by multiple peaks. Even though peak were same order magnitude before overall yearly still lower. As no juvenile or adult observed reefs collectors, it is likely that other factors are hindering island's populations. Of all materials tested, bio ball effective reproducible method monitor settlement. Panels yielded least numbers settlers, which partly explained their position close seabed. Settler collection higher mid-water layers compared bottom maximized when strings balls instead clumps. We recommend research feasibility aiding providing suitable substrate season adequate shelter increase post-settlement survival settlers. could serve a new approach assisted natural recovery.