Australian aquaculture boom at crossroads?

Aquaculture is one of the fastest growing industries in Australia with enormous future potential. But it is currently at the crossroads due to increasing competition for suitable sites.

Two possible solutions which could see aquaculture continue to expand in Australia were discussed at a Bureau of Rural Resources (BRS) seminar presented by BRS Senior Scientist, Aquaculture, Rob Cordover in Canberra last week.

"For aquaculture to continue to grow at current rates, and become an important contributor to the rural sector economy, it will need to find new areas in which to develop without the pressures, conflicts and constraints currently applying in near shore waters," he said.

Onshore marine aquaculture has the enormous benefit of being able to use land which is no longer productive for agriculture due to high levels of groundwater salinity. An estimated more than 1.5 million hectares of farmland are affected to the extent that they are unusable for either crops or livestock.

However, a method of pumping saline ground water into purpose-built evaporation ponds or basins is being used in WA, SA, NSW and Victoria. These evaporation ponds have salt levels close to that of seawater and may be suitable for growing marine fish. Where salt levels are not high enough, a short period of evaporation will raise salinity to a useful level. It can then be mixed with incoming water to maintain salt levels in the optimal range.

Trials to raise silver perch, snapper, bream, mulloway and barramundi in inland saline water aquaculture are underway in Australia.

A tropical marine seaweed commonly called 'cottoni', identified by BRS as suitable for aquaculture farming in inland saline waters, could prove a boon to farmers whose land is badly affected by rising salinity.

Cottoni is an industrial seaweed from which carrageenan, the thickener used to provide body to toothpaste and ice cream, is extracted. This tropical species grows on shallow reefs where temperatures are above 20C and salinity is between 25-40 ppt. (Normal seawater is 35 ppt). Ground water greater than 1 ppt is unusable for many applications and at 7 ppt, only non-traditional crops and pastures are possible.

"A cultivar of this seaweed has been approved by the US Food and Drug Administration for use in food production and a US company has shown a strong interest in purchasing 10,000 tonnes of dried seaweed," Mr Cordover said.

"Farmers in the Murray Darling Basin are ready to give it a try and Murray Irrigation is preparing ponds for a pilot trial.

"This seaweed is propagated from cuttings which are set into the water and just grow. In several tropical countries, including the Philippines, Indonesia, Madagascar and Fiji the seaweed clumps are tied to a line and staked out on a reef.

"Where conditions are right - and there are no storms or hungry hordes of algae eating fish, muddy water or other weed algae take over, cottoni can be harvested at about 40 tonnes per hectare. When dried to 30 per cent moisture 12 saleable tonnes can be baled for sale at about A$800 per tonne (FOB port price)."

The seaweed grows to harvest size in about 45 days at a growth rate of 5 per cent per day. Growth rates of more than 10 per cent can be achieved under better conditions.

There are other varieties of seaweed with even greater markets. The demand for edible seaweeds in Japan, China and Korea makes for a multi-million dollar market.

Offshore aquaculture also has exciting potential but it could face greater restrictions on site access.

"Offshore aquaculture could be expanded by utilizing oil platforms which are no longer being used to extract oil," Mr Cordover said.

"Such platforms can be in anything from 40-80 metres of water in Bass Strait to more than 400 metres (in the Timor Gap, north of the Western Australia-Northern Territory border 500 kilometers offshore). Typically, they are big as a football oval with plenty of room to store feed and house staff."

Advantages of going further offshore include using otherwise obsolete facilities which are already in place, avoiding resource conflicts and reducing the frequency of nets having to be replaced due to fouling. Rich inshore waters are filled with algae and barnacles which foul nets and block the flow of water that brings oxygen and removes wastes. This problem is reduced if the cages are further offshore.

Disadvantages include higher costs, the off-shore environment being exposed to the weather and strong currents, and logistical problems caused by distance requiring sturdier boats with a greater capacity to bring feed and equipment. The cages and moorings must be more robust than for protected inshore locations.

"The use of no-longer-producing oil platforms for aquaculture has been mooted in the US Gulf of Mexico. Initial trials were unsuccessful as the cages broke up against the platform in the first storm," Mr Cordover said.

"Issues to be resolved include: who will take on responsibility for maintenance of the rig during its life after oil, and who will remove the rig when it has finished its useful life."

Background

Aquaculture made up 30 per cent of the value of last year's fisheries production and was valued at $602 million.

One of the fastest growing industries in Australia, the aquaculture sector has grown by about 10 per cent per annum over the past 10 years. The industry has set itself the target to grow to $2.5 billion production in the next 10 years. To do so from its current sales base of about $600 million it intends to become the world’s most efficient producer, outstripping the current combined value of Australian seafood production by about 30 per cent.

Minister for Agriculture, Fisheries and Forestry, Warren Truss, recently announced a national agenda for Australian aquaculture. The announcement included a national advisory body to work closely with industry and government to implement the agenda and achieve its targets.

Rob Cordover is Senior Scientist, Aquaculture with the Bureau of Rural Sciences and is researching a paper on the technological potential for aquaculture development in the next 20 years.

Currently, the major products from aquaculture are pearls ($181.8 million), tuna ($166.7 million), salmon ($71.7 million), prawns ($44 million) and oysters ($46.4 million).* Sydney rock oysters have been cultivated for more than 100 years and were the first product by the Australian aquaculture industry.

95 per cent of Australian aquaculture is harvested from near-shore marine waters. Current resource use conflicts for these waters has limited the expansion of aquaculture and increased costs and investment risks.

*Australian Bureau of Agricultural Resource Economics 1998-99 figures.

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