Behaviour of temperate and sub-tropical reef fishes towards a stationary SCUBA diver

Abstract

Using remote underwater stereo–video systems we examined fish behaviour towards a stationary SCUBA diver at temperate (Rottnest Island) and sub-tropical (Houtman Abrolhos Islands) reefs in Western Australia. Changes in species richness, relative abundance, fish length, and the mean distance of individual fish from stereo–video cameras, in the presence and absence of a SCUBA diver, were assessed to infer changes in behaviour. Results show that a stationary SCUBA diver may obtain accurate measures of species richness and of the composition of fish assemblages in an area. However, the usefulness of these measures to reflect changes in fish behaviour appears limited as responses of fish towards the stationary SCUBA diver were highly species specific. Several species differed in their mean relative abundance (Heterodontus portusjacksoni, Coris auricularis, Thalassoma lunare), length (Ophthalmolepsis lineolatus, C. auricularis), and the distance to which they would approach the stereo–video systems (Kyphosus sydneyanus, Scarus schlegeli) when a SCUBA diver was present. Here, species-specific changes in the behaviour of several common and abundant fish species towards a stationary SCUBA diver advises caution to avoid biases when interpreting results obtained by SCUBA divers.

Keywords:

• Fish behaviour
• species richness
• relative abundance
• fish length
• distance
• stereo–video

Acknowledgements

This study was conducted with financial assistance from The University of Western Australia, the Cooperative Research Centre for Coastal Zone, Estuary and Waterway Management (Coastal CRC) and the Department of Fisheries, Western Australia. We thank Kim Nardi, Chris Dibden, and Scott Sherrington for their assistance in conducting field work at the Abrolhos Islands. We also acknowledge Jai Sleeman for field support at Rottnest Island, and the Rottnest Island Authority for provision of accommodation and assistance with transport. We thank Dave Gull for support with analysis of video images, Dr Trevor Willis, Dr Russell Cole, Dr Gary Kendrick, and the marine ecology group at UWA for comments and suggestions on the manuscript.