Ontogenetic shifts in the social behaviour of pairing coral reef rabbitfishes (Siganidae)

ABSTRACT

Adult rabbitfishes (Siganidae) differ from most other herbivorous coral reef fishes by forming stable pair bonds throughout their adult lives. However, little is known about the early life stages of rabbitfishes, and no quantitative evidence regarding the ontogeny of pairing behaviour exists to date. This study describes the abundance, distribution and ontogeny of social associations in juvenile rabbitfishes on the mid-shelf reefs around Lizard Island, Great Barrier Reef, Australia. Using underwater visual censuses, we surveyed an area of 5728 m² across three distinct habitat types, revealing that the abundance of juveniles varies significantly among species, size class and exposure level. Furthermore, we demonstrate a pronounced ontogenetic shift in the social associations of juveniles of Siganus doliatus and Siganus corallinus, changing from primarily solitary individuals in the smallest size class (<50 mm) to predominantly paired individuals in the larger size classes (50–100 mm and 100–150 mm). In this context, we report the presence of several mixed-species pairs of rabbitfishes, providing the first evidence for this behaviour within the family. This supports previous research, which posits that there are strong ecological drivers, rather than a solely reproductive basis, for pairing behaviour in rabbitfishes. Based on our results, we suggest that further exploration of the ecology of early life stages of herbivorous reef fishes will increase our knowledge about ecological processes on coral reefs.

RESPONSIBLE EDITOR:

• Franz Uiblein

KEYWORDS:

• Herbivory
• juvenile reef fish
• mixed-species pair
• pair formation
• rabbitfish
• schooling
• Siganus

Acknowledgements

We wish to thank the staff of Lizard Island Research Station for field support; Katia Nicolet and Jordan Casey for field assistance; and David Bellwood, Michael Kramer, Tory Chase, Franz Uiblein and three anonymous reviewers for comments on earlier drafts of the manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This research was supported by the Great Barrier Reef Foundation (SJB).