Enhancement of grazing gastropod populations as a coral reef restoration tool: predation effects and related applied implications

Abstract

In this study, we aimed to evaluate the efficacy of adding T. niloticus to control epilithic algal biomass and enhance coral recruitment on artificial substrata at a heavily fished reef in northwestern Philippines. Our main hypothesis was that with addition of trochus, the growth of algae would be lower and the number of coral recruits would be higher. The reason for trying to control algal growth through trochus grazing was to reduce preemption of space for settlement of coral larvae. Trochus was used as a grazer because it can be cultured easily and released effectively, allowing the production of juveniles and subadults in adequate numbers for local stock enhancement. We also examined any interactions between the possible beneficial effects of trochus and “seeding” the substrate with small transplanted coral colonies to promote recruitment of coral and attract fishes and any effects of trochus on the survival of the transplanted coral colonies. Aside from assisting coral recruitment, grazing of benthic algae by trochus was expected to limit competitive effects of macroalgae on coral transplants because different functional groups of benthic algae can cause coral mortality by overgrowth, shading, abrasion, and allelopathy.