Marine Protected Volumes: Incorporating oceanographic processes into the Commonwealth Marine Reserves in bioregions off Western Australia

Protected area planning emphasises conserving pattern and, indeed, the Commonwealth Marine Reserves (CMR) aim to protect biodiversity in bio-regions around Australia. However, recent approaches to systematic conservation... [ view full abstract ]

Protected area planning emphasises conserving pattern and, indeed, the Commonwealth Marine Reserves (CMR) aim to protect biodiversity in bio-regions around Australia. However, recent approaches to systematic conservation planning, particularly in pelagic areas, have highlighted the importance of accommodating oceanographic processes and thus, resultant bio-geochemical and biological responses. The Leeuwin Current (LC) is the dominant oceanographic feature off Western Australia (WA) and, despite pervasive downwelling, upwelling does occur, particularly at the shelf- edge and in canyons. Retention areas are important as the southward LC flow can rapidly transport larvae away from their natal areas. The LC also causes the shedding of eddies and these result in considerable cross-shelf transport. The current Kimberley CMR is commended as it captures shelf-edge upwelling and is adjacent to the marine parks in WA state waters. The Gascoyne CMR is adjacent to the existing Ningaloo Marine Park but, in view of the importance of upwelling, eddies and cross-shelf transport in this oligotrophic region, it would be prudent to extend the Category 2 zone eastward. The Abrolhos CMR is a strangely-shaped protected area that includes the Houtman Canyon (Category 2). The occurrence of the persistent Abrolhos Front with strong shoreward currents implicated in recruitment of rock lobsters indicates that it would be prudent to expand the Category 2 zone. The Perth Canyon is a remarkable bathymetric feature where LC eddies form and lead to cross-shelf transport and mixing. The diversity of krill in the canyon is very high and they constitute the diet of migrating endangered blue whales. Although the Perth Canyon is protected by a CMR, the critical eastern part of the canyon requires more protection and it is recommended that the entire eastern part be zoned as Category 2. Habitat modelling of endangered sperm whales has highlightes the limited protection along the shelf-edge offered by the South-West Corner CMR as most of the Category 2 zone is located over the abyss. Widening of the Category 2 area near the Albany canyons is recommended to improve protection of the habitat for sperm whales which are still recovering from Australian commercial hunting.