Testing a site‐prioritisation framework to maximise survival of seeded corals

As climate change threatens reef‐building coral populations worldwide, there is an increasing interest in restoration to assist the recovery of coral populations. Yet these efforts are limited in scale and therefore, to maximise restoration success, it is crucial to prioritise areas where outplanted corals are most likely to survive and grow.

Here, we tested and refined a framework to select sites for coral restoration using survival data of sexually produced corals (spat) from 10 species deployed across diverse habitats in the Great Barrier Reef, Australia. For each deployment site, we extracted data on abiotic and biotic factors, then scored and combined them to compute a single score for each site. We refined the relative weighting of the factors to maximise the variance in spat survival explained by the site scores. We investigated the relationship between spat survival and each of these environmental factors, as well as the combined site score. Finally, we used simulations to quantify the increase in mean spat survival expected if selecting sites based on site scores.

Our results show that spat survival generally decreased with increasing cover of benthic organisms, highlighting the important role of competition during early life stages. In contrast, the relationship between spat survival and abiotic factors was species‐specific.

Spat survival was positively related to site score in all except one of the species. However, site score predicted only a small fraction of the variance in survival, indicating a spatial mismatch between the broad scales (>100 s m) at which corals must be seeded to support recovery, and the fine scales at which spat survival is affected (<1 m). In our simulations, using site scores improved mean survival in 11 out of 12 species‐by‐reef combinations, although some of the gains were modest.

Synthesis and applications . The framework tested can improve the efficiency of seeded‐coral deployments by increasing average survival through site selection for most taxa, thereby reducing the number of deployed spat needed to achieve a target outcome. Species‐specific weighting of factors was unnecessary for many Acropora species, but may be important for other taxa.