The Otway Marine Bioregion*
The Otway Marine Bioregion extends from Cape Jaffa in South Australia to Apollo Bay in Victoria and includes the western islands of Bass Strait, such as King Island.
What characteristics distinguish this bioregion?
- Cold ocean waters originating from the southern ocean.
- Large, powerful waves.
- As you move offshore the seafloor gradient drops away steeply.
- Slow to moderate ocean currents.
- Nutrient-rich waters. Ocean nutrients ‘well-up' from deep water to the surface at the edge of the continental shelf in an oceanographic event known as the Bonney Upwelling.
- The dominace of the leathery Bull Kelp Durvillaea potatorum on shallower rocky reefs. Offshore reefs are dominated by the kelps Macrocystus angustifolia and Phyllospora comosa.
- The region is the westward limit for a number of key seaweed species.
- Intertidal animals found west of Cape Otway show significant similarities to intertidal invertebrate species at King Island and south-east South Australia.
What are some of the significant natural values of the bioregion?
- The region is a feeding aggregation area for Pymgy Blue Whales that are attracted to swarms of krill that benefit from the nutrient-rich waters.
- The Lawrence Rocks near Portland support the largest colony of Australasian Gannets (a seabird) in Australia.
- Deen Maar Island supports one of the largest breeding colonies of Australian Fur Seals in Australia.
- The imposing undersea ‘wall' in the Port Campbell area, where the seafloor plunges 20m over a short distance.
- The extensive seagrass meadows of Amphibolis antartica within Portland Bay.
- The Warrnambool to Port Fairy area is a significant calving and nursery area for Southern Right Whales.
Marine Protected Areas in the region
Discovery Bay Marine National Park
Merri Marine Sanctuary
Twelve Apostles Marine National Park
The Arches Marine Sanctuary
Cape Bridgewater Protected Seal Breeding Colony
Deen Maar (Lady Julia Percy Island) Protected Seal Breeding Colony
Logan's Beach Exclusion Zone - Southern Right Whales
* What is a marine bioregion?
A marine bioregion is a large area of the sea that through the complex interaction of ocean currents; wave energy; seawater temperature; seafloor geology and geography, displays a distinct grouping or pattern of marine plant and animal communities and species.
For example, the plant and animal species and the habitats that dominate the warm waters of the Twofold bioregion in eastern Victoria are very different to those found in the cold, open waters of the Otway bioregion in the west.
The map on the home page suggests that marine bioregions appear to be divided into distinct areas with clearly defined boundaries, but the boundaries between them are dynamic and not hard lines.
The ocean waters on Australia's continental shelf have been classified into 60 marine bioregions. Victoria's coastal waters span 5 of these regions.