Biotic affinities of rocky reef fishes, invertebrates and macroalgae in different zones of the Port Davey marine protected area, south-western Tasmania

Abstract

1. Assemblages of fishes, invertebrates, and macroalgae showed strong and predictable distributional patterns within the newly declared Port Davey marine protected area (MPA) in south-western Tasmania. Biotic assemblages in the eastern estuarine section of the MPA within Bathurst Channel were extremely anomalous, both in relation to biota elsewhere in the Port Davey region and also to those present along the wider Tasmanian and Australian coasts. Much of this variation was due to the phenomenon of deepwater emergence, with species in 5m water depth in eastern Bathurst Channel possessing a mean maximum recorded depth of 200 m, compared witho80m for the same metric when calculated for sites studied elsewhere around Australia. Deepwater emergence in Bathurst Channel was particularly notable for sessile organisms, although also evident among fishes and mobile macro-invertebrates. 2. Quantitative baseline surveys of reef-associated species were undertaken at sites interspersed among MPA management zone types and biotic community types, thereby providing an appropriate benchmark for assessing ecological changes in different management zones within the Port Davey region through the long term. Distinctive biota present in eastern and western Bathurst Channel, and eastern Port Davey, are well protected within ‘no-take’ sanctuary zones; however, a bias in location of sanctuary zones towards areas with little fishery resources resulted in less protection for the western Port Davey biota, which also extends along the open coast. Although the lack of high level protection for sites with fishery resources detracts from conservation goals, the Port Davey MPA nevertheless represents a major advance in environmental protection because the ecologically unique, fully protected locations are a necessary inclusion within any comprehensive Australian MPA network.