Coral predation and implications for restoration of Kenyan reefs: The effects of site selection, coral species and fisheries management

Abstract

Active coral reef restoration is increasingly applied for local reef management, but remains hampered by biological interactions such as coral predation (corallivory). To determine factors that drive corallivory and develop more ecology-based restoration approaches, coral and corallivore communities were characterized and fish bite mark densities quantified on natural coral colonies and fragments outplanted on small artificial structures. Six study sites were distributed equally among three levels of fisheries management at southern Kenyan reefs (fished < reserve < no-take). Obligate corallivorous fish densities strongly correlated with coral cover regardless of fisheries management level, whereas facultative corallivorous fish (mainly parrotfish) were most abundant in no-take zones. High corallivorous snail densities were associated with low coral diversity and corallivorous sea stars were scarce. Bite mark densities on natural reefs were clearly higher for branching corals, but did not correlate to coral cover, coral diversity or corallivorous fish densities. Compared to natural colonies, predation pressure was up to 24-fold greater on outplanted coral fragments and especially fierce inside no-take zones. This high predation pressure correlated with low live tissue cover of outplanted fragments. These results demonstrate that reefs with low coral cover, often targeted for restoration, do not necessarily experience greater coral predation and that improved outplanting methods and species considerations are needed to address high predation pressure on outplanted fragments. The interplay between fisheries management, reef restoration and corallivory warrants further scrutiny: while obligate corallivorous fish are unlikely detrimental to reef recovery, high densities of facultative corallivorous fish could hamper restoration efforts.