The Geographe Commonwealth Marine Reserve (CMR) lies within and adjacent to Geographe Bay south of Perth, Western Australia, and has a depth range of 15–70 m.
IMAGE: An Eagle Ray (Myliobatis tenuicaudatus) and two Pink Snapper (Pagrus auratus) on a mixture of macroalgal and sand habitat.
It is an area of high benthic productivity and high biodiversity that provides habitat for threatened and migratory seabirds, the humpback whale and blue whale, and the Western rock lobster. More information is needed in order to establish a monitoring program for this reserve, which adjoins the Ngari Capes Marine Park (in state-managed waters). This project designed a statistically robust baseline survey of the Geographe CMR to meet the research and monitoring needs of Parks Australia.
Existing information was collated on the distribution and characteristics of key habitat types (seagrasses, corals, rocky reefs and soft sediments) and associated benthic invertebrate and benthic vertebrate communities in the Geographe CMR. A statistically robust survey was designed to meet survey objectives defined with input from Parks Australia, building on and trialling survey methodologies developed for the Flinders CMR (see story Surveys of Commonwealth marine reserves: Flinders). The survey was implemented during the period December 2014 to March 2015, and the data analysis and final report will be completed by the end of June 2015.
The survey consisted of 150 Baited Remote Underwater Video (BRUV) drops across the CMR. The sampling sites were selected using the Generalised Random Tessellated Stratification survey design (see story Applying spatially balanced survey designs to monitor indicators in Commonwealth marine reserves). Additional habitat information was obtained by placing rear facing cameras on the BRUV units. The field crew were also able to deploy 50 BRUVs at known reef and seagrass features, thereby augmenting existing information on the fish communities on these features. Autonomous Underwater Video transects will be completed in late March 2015.
Preliminary analyses indicate that Geographe appears to contain one of the largest continuous seagrass beds recorded. Fish assemblages differ by depth and habitat (seagrass, reef, sand). The complete project findings will be available in June 2015.
New knowledge and opportunities
The survey approach proved a cost-effective way to provide a CMR baseline and a consistent monitoring approach that will support future comparisons between CMRs and regions. The GRTS design was supplemented with targeted reef monitoring based on expert knowledge.
Outputs and outcomes
Existing information has been collated and documented for key habitat types and associated communities in Geographe CMR. Anticipated outcomes include a statistically robust baseline of habitat extent – including a characterisation of habitat types and associated benthic communities – that will provide a basis for subsequent trend analysis to meet Parks Australia management objectives.
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