Standard Presentation 2024 Australian Marine Sciences Association Annual Meeting combined with NZMSS

Predator-prey dynamics of a boom-bust pest species throughout their vulnerable juvenile life stage (#159)

Kenny Wolfe 1 , Amelia Desbiens 1 , Peter J Mumby 1
  1. University of Queensland, St Lucia, QLD, Australia

Resilient species that benefit from and/or exacerbate habitat degradation are of interest in the Anthropocene. The Crown-of-Thorns Seastar (CoTS; Acanthaster sp.) is a notorious boom-bust species that has altered coral reefs globally. Proximal causes of CoTS outbreaks remain elusive despite decades of research and investment into upscaling manual control. Variation in predation pressure may constrain CoTS outbreaks, though empirical observations of predator-prey interactions are sparse. We identified a range of novel predators that consume and injure CoTS juveniles in their coral rubble nursery, a crucial bottleneck to adult accumulation. Consumption of juveniles (1–20 ind.d-1) was species- and size-dependent with lower consumption by smaller predators and on larger juveniles. One specialist decapod, Schizophrys aspera, consumed CoTS up to 10mm diameter and continued partial consumption on juveniles large enough to transition to coral. The density and distribution of S. aspera appear inverse to CoTS at local and regional scales, suggesting appreciable top-down control. We contextualise our results using eDNA metabarcoding to provide a comprehensive assessment of direct and indirect predator-prey pathways involving CoTS. Diverse predator communities in rubble yield the greatest control of CoTS juveniles before the switch to corallivory and maturity, which could inform the prioritisation and optimisation of control programs.