Diel release timing is a critical determinant of reef fish survival in Post‐larval Capture, Culture, and Release
Alan Gojanovic, Jennifer L. Kelley, Rohan M. Brooker, Nathan W. Price, Martial Depczynski, Thomas H. Holmes, Jan M. HemmiAbstract
Introduction
Predation is a dominant force shaping survival of coral reef fishes. Synchronous, nocturnal settlement during low‐light, new moon periods may have developed as an adaptive response to intense predation during settlement. Post‐larval Capture, Culture, and Release (PCCR), where juvenile fishes are released directly to the reef, effectively modifies the timing and conditions of settlement, potentially reducing high predation‐induced mortality during settlement. Without targeted refinement of its protocols, PCCR may fail to confer survival benefits over natural settlement. Understanding how factors such as diel release timing shape post‐release survival is therefore essential for improving restoration outcomes.
Objective
This study aimed to test how diel release timing influences behavior, predation exposure, and early post‐release survival of a coral reef fish ( Pomacentrus amboinensis ) under short‐term PCCR.
Methods
Fish were captured before settlement and individually released onto experimental patch reefs at either 09:00 or 17:00 hours following a 4‐ to 5‐day rearing period, adjusted to ensure equal average age at release. Post‐release behavior was quantified, survival monitored over 48 hours, and interval‐specific mortality rates modelled to examine the role of release timing on PCCR outcomes.
Results
Fish released in the morning survived significantly better than fish released in the afternoon. Predation was highest in the immediate post‐release period regardless of release timing, but worse for afternoon releases, creating a survival gap that persisted across the 48‐hour monitoring period.
Conclusion
We identify diel release timing as an important determinant of PCCR success. Releasing fish at a time of day that maximized experience acquisition enhanced post‐release survival.