South East Australia
The south-east Australia hotspot is an area of over 301,900 km2 and is situated along the densely populated eastern seaboard of Australia, off the coast of the states of New South Wales (NSW), Victoria and Tasmania. It extends from the shoreline to a distance of approx 6000m offshore and takes in 4.3% of the Australian EEZ. The area is contains one of Australia’s busiest shipping lanes and location of six Commonwealth Fisheries. The hotspot area is also used extensively for recreation and contains numerous National Parks and Marine Reserves.
The south-east Australian hotspot is strongly influenced by the East Australian Current (EAC). The EAC flows south along the edge of the continental shelf, carrying tropical water south before retroflecting towards New Zealand and forming the Tasman Front. South of the EAC are the cool waters of the sub-Antarctic zone which move up the east coast when the EAC retracts north in winter. Flow is strongest in summer, often seen as a tongue of warm water extending south into waters off eastern Tasmania. Inter-annual variability also can also result in warmer than average conditions, and already impacts the region in some years.
Economic and social context
In terms of industry value added the south east marine region’s largest two marine based industries are marine based tourism and offshore oil and gas. These two industries together account for around four-fifths of the region’s industry value added, while the remaining fifth is accounted for mainly by aquaculture and commercial fishing, ports, ship building, and shipping activities (ABARE).
In terms of the gross value of fisheries production, aquaculture contributes around a quarter of this, state wild catch fisheries 60 per cent, and Commonwealth fisheries 15 per cent (ABARE). In south-east Australia the commercial fishing sector is contracting and the associated fishing communities are re-orienting to other marine and non-marine sectors.
Major commercial fisheries include blacklip abalone, southern rock lobster, Australian salmon, snapper and southern calamari which are harvested in all south-eastern jurisdictions except the Commonwealth. Some species groups, such as the small pelagic fishes and flatheads are harvested in all five jurisdictions (states plus the Commonwealth).
Commonwealth Fisheries in area include the Eastern Tuna and Bill Fish Fishery, Eastern Skipjack Tuna Fishery, Commonwealth Trawl Sector, Small Pelagic Fishery, Southern and Eastern Scalefish and Shark Fishery, and the Southern Squid Jig Fishery.
Recreational fisheries are important in the south-east and include whiting (fam. Sillaginidae, e.g. King George whiting Sillaginodes punctata), flathead (fam. Platycephalidae), Australian salmon (Arripis spp.), bream (fam. Sparidae), mullet (fam. Mugilidae), garfish (fam. Hemiramphidae), tailor (Pomatomus saltatrix), and pink snapper (Pagrus auratus).
There is very little indigenous fishing in the south-east Australia region.
Biodiversity of the region
The ecology and biology of the species found in the south-east hotspot region are diverse, with molluscs, crustaceans, teleosts, and elasmobranches represented and a high number of endemic species. A wide range of habitats are utilised by key species including benthic, demersal and pelagic environs, as well as estuarine, neritic, and oceanic waters and rocky reef, soft sediment and vegetated substrates. Juvenile stages commonly occupy a different habitat to the adult stages, typically inhabiting shallow coastal waters and estuaries. The majority of commercial species are distributed from NSW to southern Western Australia; however, some have large-ranging cosmopolitan distributions (e.g. large pelagic fishes) and others have more restricted distributions (e.g. eastern king prawn, school prawn, and dusky flathead). All species are broadcast spawners with a pelagic larval phase, except for gummy sharks and southern calamari; however, the duration of the larval stage varies extensively between species (e.g. <2 weeks in abalone and 1–2 years in southern rock lobster). Species occupy a range of trophic levels, from detritivores and herbivores to apex predators.
- As the warm East Australia Current (EAC) extends south, the distribution of a number of warmer water species of seaweed, plankton, molluscs, demersal and pelagic fishes are also extending south.
- Recruitment and catch of southern rock lobster, one of the regions’ major fisheries, appears to be negatively impacted by regional warming.
- There is a major decline in algal habitat in inshore waters of Tasmania due to the southward expansion of the lomgspine sea urchin aided by the EAC
- Reduced calcification rates of mollusks and deepwater corals have been recorded
- Temperate species of macroalgae are at risk of extinction