Grazing halos—barren areas of sand that surround coral patch reefs in otherwise continuous seagrass plains—form due to predator avoidance by herbivorous fish and echinoderms that preferentially graze seagrasses close to the safety of the reef structure. Grazing halos are readily visible from satellite and aerial imagery and halo size may be indicative of local predator abundance. This study analyzed grazing halos in the South Water Caye Marine Reserve (Belize) and the Florida Keys National Marine Sanctuary (U.S.A) using remote sensing techniques and field surveys. More than 22 patch reefs were analyzed in both no-take conservation zones and paired sites. At each patch reef herbivore behavior was determined using grazing assays and video surveys deployed along transects from the reef edge. Fish abundances, reef rugosity, and urchin abundances were quantified at each patch. Mixed linear effects models were used to determine relationships between patch characteristics (predator, herbivore, and urchin abundance, rugosity, etc.) and various indices of grazing and spatial habitat use.
As one of nearly 20 students whose international research projects are being funded this summer by the F&ES-based Tropical Resources Institute (TRI), ...
