Zoological Studies

Vol. 57, 2018

(update: 2018.01.18; 02.05)

Ephemeral and Localized Outbreaks of the Coral Predator Acanthaster cf. solaris in the Southwestern Lagoon of New Caledonia

Mehdi Adjeroud1,*, Mohsen Kayal2, Christophe Peignon2, Matthieu Juncker3, Suzanne C. Mills4, Ricardo Beldade4,5, and Pascal Dumas2

1Institut de Recherche pour le Développement, UMR 9220 ENTROPIE & Laboratoire d’Excellence CORAIL, Université de Perpignan, 52 Avenue Paul Alduy 66860 Perpignan, France
2Institut de Recherche pour le Développement, UMR 9220 ENTROPIE & Laboratoire d’Excellence CORAIL, Centre IRD de Nouméa, BP A5, Nouméa, New Caledonia. E-mail: mohsen.kayal@gmail.com
3OEIL, Observatoire de l’Environnement, Province Sud, Nouméa, New Caledonia. E-mail: matthieu.juncker@oeil.nc
4PSL Research University, EPHE-UPVD-CNRS, USR 3278 CRIOBE & Laboratoire d’Excellence CORAIL, BP 1013, 98729 Papetoai, Moorea, French Polynesia. E-mail: suzanne.mills@univ-perp.fr
5MARE - Marine and Environmental Sciences Centre, Faculdade de Ciências da Universidade de Lisboa, Campo Grande, 1749-016 Lisboa, Portugal. E-mail: rbeldade@gmail.com

(Received 10 November 2017; Accepted 10 January 2018; Communicated by Yoko Nozawa)

Mehdi Adjeroud, Mohsen Kayal, Christophe Peignon, Matthieu Juncker, Suzanne C. Mills, Ricardo Beldade, and Pascal Dumas (2018) Outbreaks of the coral predator Acanthaster spp., the crown-of-thorns seastar (COTS), cause major coral declines across the Indo-Pacific. However, the processes surrounding the initiation and propagation of COTS outbreaks are still unclear. We observed COTS outbreak abundances on several mid-shelf and inner-barrier reefs in the southern section of the New Caledonian lagoon, a multi-location initiation event that we expected to precede a broader region-wide disturbance. However, reef monitoring over 3 years revealed the highly localized and ephemeral character of these outbreaks. Outbreaks that were observed at four reef locations at the beginning of the survey simply faded away, without any specific management actions such as culling efforts. We also found no distinct reef biotope on which COTS outbreaks originated, although mid-shelf and inner-shelf barrier reefs seem to be favoured. New Caledonia has been exempted from to widespread regional COTS outbreaks, which is surprising given its proximity to the Australian Great Barrier Reef - a reef complex particularly vulnerable to COTS - and Vanuatu - where large-scale outbreaks were recorded during the same period. The availability of coral prey is probably not a limiting factor for the propagation of COTS outbreaks on New Caledonian reefs, given the high abundance and diversity of coral assemblages. Our findings reveal that localized and ephemeral COTS outbreaks can be naturally contained and do not necessarily result in widespread disturbances.

Key words: Coral reefs, Acanthaster, Predator outbreaks, Monitoring, Spatio-temporal variation, New Caledonia.

*Correspondence: Tel: +33695540495. E-mail: mehdi.adjeroud@ird.fr