Coral propagation: a review of techniques for ornamental trade and reef restoration

Aquaculture of coral offers an alternative to wild harvest for the ornamental trade and shows considerable promise for restoring reefs and preserving biodiversity. Here, we compare advantages and disadvantages of asexually derived fragments versus sexually derived propagules and in situ versus ex situ nursery phases for the ornamental trade and reef restoration. Asexual propagules, sourced from a donor coral colony that is cut into smaller parts and attached to artificial substrate, are most commonly used. The most suitable corals are typically branching species, although fragments from species with other growth forms can be successful, albeit slower growing. Sexually derived propagules are collected from the wild or from colonies in aquaria during spawning, with an artificial substrate provided for settlement. The timing of spawning is known for many broadcast spawning corals, but opportunities for collection of gametes are generally limited to only once or a few times per year. Brooding species with multiple periods of larval release provide better options for culture of sexually derived propagules. Propagation techniques have developed considerably over the past 20 years, yielding faster growth rates, reduced mortality and reduced detachment from substrates. Simple and cost–effective propagation techniques can be used to restore denuded reefs, preserve endangered species, provide live corals to the international ornamental trade, enable livelihood diversification for coastal communities and provide experimental materials for marine research. This review provides a comprehensive synthesis of recent developments in aquaculture propagation techniques for the purpose of ornamental trade and coral reef restoration, including asexual and sexual propagation, nursery and transplantation stages.