With the movement of international and domestic shipping traffic throughout Australian ports, there is an increased risk of introducing exotic marine pests into Australian waters: including through the expulsion of ballast waters from contaminated ships . Once established exotic marine pest species have the capacity to wreak havoc in the marine ecosystem through competition with native species for food and habitat, or by predating upon native species themselves. One of the most obvious and direct economic consequences likely to arise from marine pest invasions is the loss of commercial and recreational fishing stock .
The serious nature of economic repercussions arising from marine pest invasions associated with Australian fisheries is illustrated by the recent outbreaks of the exotic seaweed Caulerpa taxifolia in South Australia. It is likely that this pest was introduced initially into Australia as an aquarium strain which when released into open water has developed into an exotic pest. There is a real concern that the fisheries and aquaculture industry in SA could be ruined by this seaweed which has the capacity to reduce fish numbers by overgrowing their feeding grounds. Consequent declines in fishery productivity would be catastrophic given that the fisheries and aquaculture industries are collectively valued at $500 million . Similarly, the presence of the marine pest invader Asterias amurensis, or the Pacific starfish, potentially threatens shellfisheries in affected waters off Tasmania and Victoria. While little is known about the impact the pest is having in Australian waters, in Japan it has cost the country millions of dollars in lost production and management and cleanup costs . In another example, the Pacific oyster has been identified as marine pest species that preys upon and competes with the Sydney rock oyster, which was worth $32 million to the NSW economy alone in 2000-2001. The complicating factor in this case is that the Pacific oyster was deliberately released into Australian waters as an aquaculture species. More information about the Pacific oyster can be found in the information sheets on the economic value of estuarine commercial fisheries and the economic consequences of aquaculture . There are many more examples of marine pests that are or have the potential to threaten fisheries productivity throughout Australia, but these examples suffice to illustrate the direct economic threat they can pose.
In terms of indirect economic impacts, the presence of marine pests is impacting on the operation of seaports. Governments throughout Australasia are increasingly putting restrictions on the movement of ships, which are at high risk of carrying the pests . For instance, ships entering Australian waters deemed to be at high risk of carrying exotic marine pests may be required to carry out management actions to prevent the spread and establishment of pests in Australian waters. Such actions include the discharge of ballast waters outside of Australian waters by ships entering into this zone . In New Zealand, the government has responded to the potential threat of contamination of their waters by the Seastar from Australia, by invoking its Biosecurity Act and the National Ballast Water Management System. These measures taken by the New Zealand Government prevent ships coming from the affected regions in Australia from dumping their ballast water in New Zealand territory .
These measures may result in economic positives with the protection of the marine environment from marine pests, however, theey are also expected to hinder and slow down shipping trade between Australia and New Zealand. This is a prospect of particular concern given the valuable nature of port activities to local economies in Australia . To give an indication of the potential value of port activities to a local economy, the Port of Melbourne contributes in excess of $5 billion per annum to Victoria's GDP . For more information on the scale of economic losses that could be incurred due to the invasion of ports by marine pests, see the information on human-made capital.
A substantial amount of money is spent trying to prevent the establishment of marine pest invaders in Australian waters. These efforts are realised through a series of management plans. The general objective of these plans is to first prevent the establishment of marine pests in Australian waters. Management programs that have been introduced into Australia include the Introduced Marine Pests Program, introduced at a cost of $4.5 million, and the Invasive Marine Species Program and Ballast Water Mitigation Program which were initiated at a cost of $1 million each . Should marine pest outbreaks occur regardless of these measures, costs are again incurred in the process of cleaning up and controlling the outbreaks. In Darwin, an outbreak of the black-striped mussel cost $2 million to control. The economic consequences of doing nothing would most likely have been devastating had the mussel become established, as it would probably have menaced the pearling industry in the region which is estimated at $225 million .
The Port of Brisbane undertook measures in 2000 that could ultimately diminish the costs associated with pest removal should pest outbreaks occur. The measure undertaken in April 2000 was a baseline study of the port specifically seeking to identify the presence of target marine pests. The benefit of studies like these, if undertaken on a regular basis, is that outbreaks of marine pests may be detected at an early stage when they can be contained at considerably less expense than is required to both control and compensate for an advanced marine pest explosion . Ultimately, it is ideal that marine pest outbreaks in Australian waters are prevented. Primarily, this is because of the large expanse of the Australian coastline, which makes it particularly difficult to monitor ships and prevent the further spread of organisms to other parts of the country . The occurrence of pests or disease in agricultural products has been used as a barrier to Australian industries trading with the USA. It is not inconceivable that one of the more devastating economic impacts of exotic marine pests could ultimately be the closure of infected ports to overseas shipping.