Improving ex situ coral culture outcomes: growth and survival responses of Galaxea fascicularis recruits to supplemental feeding

Nutritional supplementation can improve coral recruit performance by enhancing growth and survival, two key metrics for the success of sexually propagated coral restoration. We investigated the effects of three feeding regimes (Control, 1 feed/week, and 2 feeds/week) using powdered commercial coral feed on Galaxea fascicularis recruits over a 23-week period in land-based nurseries. Growth was assessed weekly as budding polyps per recruit, and survival was analyzed using Kaplan–Meier survival curves and log-rank tests. Treatment effects on growth were further evaluated using a generalized linear mixed-effects model (Gamma distribution with log link), including Treatment, Week, and their interaction. Survival differed significantly among treatments, with the twice-weekly feeding group consistently exhibiting higher survival rates than the Control and once-weekly feeding groups. After 23 weeks, survival was highest under twice-weekly feeding (41.3%), followed by once-weekly feeding (29.2%) and no feeding (24.7%). Growth analyses revealed significant main effects of Treatment and Week, as well as a significant Treatment × Week interaction, indicating accelerated growth under more frequent feeding regimes. Our findings demonstrate that frequent supplemental feeding substantially improves both survival and growth of G. fascicularis recruits in ex situ nurseries. Twice-weekly feeding provided the greatest benefits, highlighting the importance of optimized nutritional regimes for coral propagation. These results offer practical guidance for improving husbandry protocols and enhancing the efficiency of sexually propagated coral restoration efforts.