The design of a child's playpen has been adapted for new technology in fish farming. Two west-coast salmon farms have participated with Bord Iascaigh Mhara (BIM)in a pilot project to try out more flexible, efficient offshore cages.
The "Ocean Spar" cages are made by a US company and have already been tested on the far side of the Atlantic. Resembling a playpen submerged in water, with a net bottom and top, the cage sits vertically in the sea and is so taut that it is "transparent" to wave energy and currents. In other words, the net doesn't move with the sea, allowing for more space and far happier fish.
Following a fact-finding visit to New Brunswick, Canada, in October 1998, two west-coast farms agreed to participate with BIM in a project to evaluate the system, which also offers scope for larger stocking density. Killary Salmon Company in Galway was the first guinea-pig on a fairly sheltered site in the fjord. A hexagonal cage with a 20,000 cubic-metre capacity was installed in Mayo in 1999 and was stocked during that summer.
There were several teething problems: harvesting and lice treatment had to be carried out with the prevailing current and tide. However the cage's unique design virtually eradicated attacks by seals and the vertical walls improved the environment for the fish.
During the first 18 months Mr James Ryan of Killary Salmon Company reported that no maintenance of the cage structure or net was required, other than a few dive checks on lines and moorings. Improved stocking density would see significant cost savings, he predicted.
Last year another Ocean Spar cage was installed at a far more exposed site north-east of Clare Island in Co Mayo, a site of Clare Island Seafarms. Rather than stock it immediately and risk losing fish, the farm monitored its performance during the winter months and began stocking a month ago.
Currently the cage is about half full and is performing well so far, according to Mr David Baird of Clare Island Seafarms. He believes the technology may make offshore sites far more accessible.
Mr Donal Maguire, BIM's aquaculture development manager, is confident that the technology may be adopted by other farms here allowing Ireland to increase farmed fish tonnage without any adverse environmental impact. The lessons learned at Killary over a three-fish cycle have proved very valuable, and fish farmers who met Mr Maguire this week in Westport, Co Mayo, have expressed keen interest.