Proposals for marine reserves require a clear understanding of the habitats. Marine communities and species to be protected within a reserve and the degree to which these will be represented in any final reserve proposal. In most cases, dive based surveys are necessary during the process of boundary delineation, particularly where information, such as the depth range, degree of exposure and offshore extension of reefs. is limited. The present report describes the results of a diving survey in Port Davey. southwestern Tasmania, which investigated the distribution of different reef habitat types.
At Port Davey, a large marine reserve has been proposed to protect both a "unique" ecosystem, and a "representative" ecosystem. The "unique" ecosystem is a consequence of the dark tannin-stained surface water found in Bathurst Harbour. Bathurst Channel, and Port Davey, whose origins lie in the south-western rivers. including the Old River and the Davey River. ln the calm waters of Bathurst Harbour and Bathurst Channel. this dark stained surface water limits light penetration. allowing plant communities to be replaced by invertebrate assemblages in shallow waters, a process not known to occur on the same scale elsewhere around Australia. As this dark water enters Port Davey from Bathurst Harbour it is dispersed by ocean currents and vertical wave-induced mixing. However. Breaksea 1s and the coast adjacent to the mouth of Bathurst Channel are greatly influenced by the tannin waters, so should be considered an exposed coast ex tension of this unique system.
The "representative" ecosystem that is proposed to be protected in Port Davey is intended to include representative examples of habitats (particularly reef found in the Davey Bioregion (see Edgar et al. J 997) of Tasmanian waters. a region influenced by the West Wind Drift, and high energy swells. The habitats potentially protected in this proposal include sheltered embayments such as Hannant Inlet and Kelly Basin, ranging through to the maximally exposed reef found in outer Port Davey.
While many of the "unique" tannin influenced habitats have been studied during previous surveys (e.g. Edgar 1984a, Last and Edgar 1994), little is known of the distribution of "representative" habitats within Port Davey itself, and the boundaries between representative coastline and that strongly influenced by tannin waters emanating from Bathurst Channel and the Davey River.
The aim of this survey was to aid in the delineation of appropriate reserve boundaries. by examining the distribution. range, and extent of reef habitats within Port Davey. This was to be achieved by conducting qualitative and quantitative surveys of reef communities a1 as many locations as possible in Port Davey over a seven day period.
Barrett N.S., Edgar G.J., and Mooney P.
Technical Report for the Tasmanian Aquaculture and Fisheries Institute