Changes in the fish assemblages along the Busselton Jetty, and a comparison with natural habitats

Context In Western Australia, the heritage-listed Busselton Jetty is a popular tourism, fishing and diving destination renowned for its unique marine communities. Aims This research describes and quantifies the fish assemblages (mean number of individuals, species diversity and biomass) at the Busselton Jetty, and makes comparisons with natural habitats in Geographe Bay. Methods Diver-operated stereo-video systems filmed 25-m transects along the length of the jetty, and a remotely operated vehicle stereo-video filmed 25-m transects in nearby reef, seagrass and sand habitats. Fish at all habitats were counted, identified and measured. Results Fish assemblages at the defined inshore, mid-shore and offshore zones of the jetty differed significantly, whereas the number of fish, species diversity and biomass increased with distance from shore. There was no measurable effect of protection within the small sanctuary zone at the end of the jetty. Fish assemblages at the jetty differed from those in all three natural habitats, and the number of fish, species diversity and biomass were highest at the natural reef, followed by the jetty, the seagrass and the sand habitats. Conclusions The Busselton Jetty supports a distinctive fish assemblage, high species diversity and a variety of benthic communities. Changes in the fish assemblages were attributed to differences in habitat type, complexity, depth and distance from shore. Implications The ecological and social benefits of future man-made marine structures can be optimised by incorporating design features that promote habitat diversity and complexity.