Coral larval enhancement with and without nets yields similar recruitment during slack current releases

Abstract Introduction Restoring coral reefs through larval enhancement has the potential to scale interventions beyond experimental plots of tens of m 2 . However, the effectiveness of releasing larvae without confinement (“free release”) remains untested. Understanding how confinement duration and larval density affect settlement and post‐settlement survival is essential for designing logistically effective and scalable restoration strategies. Objectives This study examined whether naturally occurring slack current periods (lasting approximately 2.5–3 hours) can retain larvae over target reefs and support recruitment comparable to net‐confined methods. Methods Coral larvae were released onto reef plots during slack currents under four treatments: free release, net confinement for 2.5 and 24 hours, and two larval densities (44,000 vs. 22,000 larvae.m −3 ) for the 2.5 hour treatment. Settlement and recruitment were monitored over 15 months on tiles and adjacent natural reef substrate, comparing recruit density, survival, and growth. Results All treatments yielded significantly higher settlement than natural background rates, with net‐confined treatments producing 4–7 times more initial settlers than free release. However, after 15 months, recruit densities were similar across treatments, indicating density‐dependent mortality in the first 8 months. Survival on tiles was low (<0.25), though improved by gregarious settlement, chimerism, and settlement near edges. In contrast, survival on reef substrate was 2.5–3.5 times higher, highlighting the influence of microhabitat and the need for reef‐based metrics to assess restoration success. Conclusions Although free release during slack currents resulted in lower initial settlement, long‐term recruit densities were comparable to net‐confined methods, demonstrating its promise as a scalable coral restoration strategy.