-Ahstract. We studied influence of piscivorous fishes and prey refuges on assemblages of fishes occupying 52 model reef in a large seagrass bed off St.thomas , U.S. Virgin Island. We conducted three experiments; two involving 6 reef each . lasting 2and 5 yr , and one involving 40 reef . lasting 1yr . EAC H experimeant included replicate reef in various combinations of five structural trcatments; holcless controls, 12 and 24 small holes, and12 and 24 large holes.