Predator identity and recruitment of coral-reef fishes: indirect effects of fishing

Studies of food and interaction webs are often simplified by combining different species of predator into guilds, especially predators that are closely related. Such combinations require the assumption that predators are functionally redundant or at least have similar effects on prey abundances and community structure. However, few studies have rigorously tested this assumption, particularly with exploited species of marine predators. Moreover, fishing can strongly alter the relative abundances of different predatory species, further highlighting the need to examine the top-down effects of different predators on lower trophic-level species within marine communities. Throughout the greater Caribbean, intensive fishing has depleted populations of Nassau grouper Epinephelus striatus, while populations of the less-targeted coney Cephalopholis fulva have proliferated. In the present study I experimentally tested the effects of these different grouper species on recruitment of other coral-reef fishes to spatially isolated reefs. Recruitment to reefs occupied by Nassau grouper was similar to that on predator-free control reefs, and both treatments accumulated higher relative recruit abundance and diversity than reefs occupied by coney. Thus, even closely related predator species can have substantially different effects on lower trophic levels. Shifts in dominance of predatory species may therefore lead to dramatic changes to prey communities. These findings underscore the importance of addressing both the direct and indirect effects of fishing on marine communities.