GRAZING HALOS AND PREDATION ON JUVENILE CARIBBEAN SURGEONFISHES

In the Caribbean, recruitment of a number of fishes has been found to be low at the edges of patch reefs, intermediate in the grazed halo an d highest in dense seagrass. This has been attributed in part to the a ctivities of reef-based predators. We presented small surgeonfishes he ld in clear glass bottles at 4 distances up to 20 m from the edges of reefs and found that the rate of encounters with predators (and aggres sive territorial herbivores) was high at the reef edges, but encounter rates in the halo were much lower and similar to those in the dense s eagrass. The low rate of interactions even 2 m from the reef edge impl ies that reef-based predators avoid the halo also, presumably because of the risk to themselves of predation from still larger piscivores. T his implies that the pattern of recruitment is due to avoidance by rec ruits rather than the depredations of reef-based predators. Many surge onfishes recruiting to experimental structures in the seagrass were mi grant juveniles rather than settling larvae and we suggest that the gr adient in recruitment of surgeonfishes reflects proximity to preferred post-settlement habitats.