PREDATOR-PREY INTERACTIONS BETWEEN GRAY TRIGGERFISH (BAL1STES CAPRISCUS GMELIN) AND A GUILD OF SAND DOLLARS AROUND ARTIFICIAL REEFS IN THE NORTHEASTERN GULF OF MEXICO

摘要

Densities of sand dollars (Encope michelini Agassiz, Mellita tenuis Leske, Leodia sexies-perforata Leske, Clypeaster subdepressus Gray) were sampled with increasing distartce from four artificial reefs in the northeastern Gulf of Mexico from April through August 1991. I tested the hypothesis that gradients of prey (sand dollar) densities differ between reefs of different spatial configurations occupied by a known predator, the gray triggerfish (Balistes capriscus). I observed a significant, positive relationship between sand dollar density and distance from reefs and qualitative differences in sand dollar densities between reefs of different spatial configurations. Experiments using three species of tethered sand dollars (Encope michelini, Mellita tenuis, Leodia sexiesperforata) suggest gray triggerfish prefer M. tenuis and L. sexiesperforata over E. michelini and have an approximate foraging radius of 20 m from reefs where refugia are aggregated and 30 m or further at reefs where refugia are dispersed.