The Republic could spearhead a "blue revolution" with the design of submarine fish cages for open ocean locations, according to Bord Iascaigh Mhara (BIM).

The use of totally submerged cages anchored offshore could produce healthier, faster-growing fish in larger quantities, BIM's aquaculture division says. It could also multiply production in the Irish aquaculture sector, increasing current output by 150,000 tonnes with a first sale of €500 million annually.

Current Irish production of finfish is just over 18,000 tonnes, valued at €54.5 million in 2003.

The Food and Agriculture Organisation (FAO) has predicted that world requirements for seafood will reach 180 million tonnes by 2030 - or 40 per cent more than current output from both the catching and fish farming sectors. However, due to rising fuel prices and stock pressures on commercial exploitation of wild fisheries, the FAO predicts a growing gap between supply and demand that may only be met by aquaculture's expansion offshore.

BIM and the Marine Institute believe that "farming the deep blue" - the title of a conference the agencies hosted in Limerick this week - represents a €21 billion opportunity for the global marine farmed fin-fish industry.

The agencies point out that demand for seafood products in the EU, US and Japan has doubled in past 30 years.

In the Atlantic region alone, it is reliably forecast that annual production will need to rise by at least 3.15 million tonnes, valued at €9.5 billion per annum, if it is to meet the market demand by 2030.

The solution may lie in using "blimp" style cages that are built to withstand Atlantic weather, according to Mr Donal Maguire, BIM's aquaculture development manager, who chaired the international conference in Limerick.

He believes that Ireland has at least 15 sites for such offshore technology.

In theory, these submerged cages could hold up to 1,000 tonnes of fish, and would be anchored to a seabed food store.

Remote operation of feeding from land would be fuelled by a surface buoy equipped with electricity generation systems.

The food store would be refilled periodically from a supply ship, and the fish would be harvested by disconnecting and floating the cage and towing it inshore.

Much depends on technological design, however, at a time when the Atlantic is getting rougher.

A vote establishing an international council to research such possibilities was taken in Limerick, as part of a bid to create a "global high-tech virtual community", according to Mr Maguire.

BIM has been working with the University of Limerick on creating this international community, which would draw in the best of technological expertise.

Even if there was no projected shortfall in seafood supply, aquaculture is already under pressure in coastal zones, due to competition for space, Mr Maguire says. "Population increases worldwide tend to be focused in coastal zones," he notes.

There are also obvious environmental benefits to offshore aquaculture sites - as the award-winning Clare Island fish farm off Co Mayo has already proven.

Impacts on the seabed are limited, there is minimal interaction with migratory wild fish stocks, and fish grown at offshore sites have firmer flesh, lower fat levels and fewer problems with sea lice.

However, these "Class 3" or semi-exposed sites rely on cages that can withstand severe wind and wave conditions and ocean swell.

They will serve as "technology incubators" for developing Class 4 or ocean locations, according to Mr Maguire.

A move offshore among Irish fish farmers would not only promise increased output, but could also generate an extra €250 million in ancillary business, and support 4,500 extra jobs, BIM says.

"All of this wealth creation and employment would be located in Ireland's most vulnerable peripheral coastal communities, building on the expertise of Irish finfish farmers," it adds.