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Characteristics of the fish faunas of artificial reefs in Geographe Bay determined from video footage collected by recreational fishers

Walker, Timothy Hugh Elliot (2016) Characteristics of the fish faunas of artificial reefs in Geographe Bay determined from video footage collected by recreational fishers. Honours thesis, Murdoch University.

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The number of artificial reef deployments around Australia has increased in recent years due to their popularity amongst recreational fishers. As these reefs modify the environment and its associated fauna, monitoring is required to ensure that any negative impacts to the surrounding area are assessed and minimised. Given this and the high cost of purpose-built artificial reefs, there is a need to develop cost-effective monitoring methods to determine their faunal composition. To address this need, this thesis reviewed methods for monitoring the faunas of artificial reefs and utilised the Baited Remote Underwater Video (BRUV) method to survey the fish faunas of two artificial reefs in Geographe Bay.

Fourteen fauna monitoring methods, in their application to artificial reefs, were critically evaluated against five criteria, i.e. deployment, accuracy, precision, time and cost. Not all methods were found to be applicable to the different types of artificial reefs, with the accuracy of each technique depending upon the scale at which monitoring occurs and the type of fauna being targeted. The fastest and cheapest techniques were those that either utilised only minimal equipment and/or did not require observers. Remotely operated underwater video, particularly BRUVs, were found to provide a relatively inexpensive and effective tool for monitoring fish communities of artificial reefs.

This finding supported the choice of the BRUV method, which was deployed through citizen science, to monitor the fish communities of the Bunbury and Dunsborough artificial reefs in Geographe Bay, south-western Australia, between October 2015 and July 2016. The resultant videos were analysed, using two-way ANOVA, to determine if the number of taxa, total MaxN, Simpson’s Index, as well as the MaxN of several key recreational species, differed between reefs and over time, whilst PERMANOVA was utilised to identify whether the composition of the fish communities differed spatially and temporally. Most of the 60 taxa recorded were resident teleosts, however, nine species of elasmobranch were also recorded. In terms of the number of individuals, most were either pelagic or epibenthic and fed on zooplankton or zoobenthos. Significant differences were found among reefs in all variables, except Simpson’s Index, with greater values typically being recorded on the Dunsborough reef. Monthly differences were detected for the number of taxa, total MaxN and the abundance of two recreationally important species, with greater values occurring mainly during summer. The greatest differences in the above univariate variables and fish community composition were always found for the reef factor, indicating that the location of the reefs to nearby habitat was predominantly responsible for shaping their associated fish communities. The lower, but still influential, temporal differences were influenced by seasonal changes in water temperature and oceanographic currents.

The data collected during this study demonstrate that BRUVs, deployed through citizen science, can be a useful and cost-effective tool for monitoring the fish faunas of artificial reefs.

Item Type: Thesis (Honours)
Murdoch Affiliation(s): School of Veterinary and Life Sciences
Supervisor(s): Chaplin, Jennifer and Tweedley, James
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