Employing invertebrates to restore herbivory on Caribbean coral reefs: recent developments and remaining barriers

With coral reefs in global decline and further threatened by growing anthropogenic impacts, effective strategies for restoring these critical ecosystems are increasingly sought after. In Caribbean reefs, where disease outbreaks and fishing pressure have reduced herbivore abundances and facilitated widespread phase shifts from coral to algal dominance, herbivorous invertebrates have gained recent attention as a promising restoration tool. However, many restoration practitioners face challenges in evaluating the feasibility and anticipated outcomes of integrating invertebrate herbivores into their programs. Here we review recent developments regarding species and techniques and identify remaining barriers that require further research attention before invertebrate enhancement can be considered a scalable strategy for restoring Caribbean reefs. Bottlenecks in mariculture processes remain in the larval and juvenile rearing stages for many species that impede the scalability of invertebrate production, with significant outstanding challenges across all species in terms of stocking effectiveness and monitoring feasibility. Integrating alternative herbivorous invertebrate species can ameliorate some of these bottlenecks, and investigating the culture feasibility and grazing effectiveness of additional species holds notable research opportunities. Across research and restoration initiatives, ecological objectives and viable techniques for measuring outcomes against these objectives are needed. These findings establish research priorities for restoration and invertebrate husbandry communities alike and provide guidance for practitioners in the critical and rapidly evolving field of coral restoration.