Abstract
Some coral species in natural reef systems derive benefits from fish which live in close association with them. This study investigates the benefits of incorporating fish in ex situ coral culture to enhance coral physiological performance. Corals that typically have fish associations (Acropora kenti and Pocillopora verrucosa) and those that do not (Porites lutea and Platygyra daedalea) were grown in aquaria under different fish-associated treatments for 3 months. Physiological performance of the corals, including growth, protein content, symbiont density and photosynthetic efficiency were assessed in the different treatments where corals were (1) kept with a school of Chromis viridis fed a pelleted diet, (2) supplied filtered water from a tank housing C. viridis, (3) fed live feeds whilst maintained with C. viridis, (4) supplied only with live feeds, (5) supplied with a pelleted fish diet without C. viridis and (6) not supplied feeds and without C. viridis. Whilst the responses of the corals varied between species, generally, exposure to fish or fish-water increased the protein and/or symbiont density within coral tissue. A. kenti and P. lutea, which derive a higher proportion of their energy requirement from autotrophy, displayed improved growth in the fish treatments, whilst the more heterotrophic P. verrucosa grew fastest when supplied with live feeds. The more heterotrophic, slow-growing P. daedalea did not show significant improvements in growth under any of the treatments, and there were no major differences in photosynthetic efficiency between treatments in any of the corals. These results indicate that incorporating fish into coral culture could provide an accessible source of nitrogen and phosphorous enrichment via the dissolved portion of the fish's wastes and, in turn, enhance the growth of corals more reliant on autotrophy, like Acroporids. The results point to potential efficiency gains for coral husbandry practices, with the aim of satisfying the growing demands of reef restoration and ornamental aquaculture.