THE IRISH aqua-culture industry is harvesting mussels in a more environmentally friendly and efficient manner than ever before as a result of a Bord Iascaigh Mhara (BIM) initiative to bring new technologies to Ireland.
The sea fisheries board has carried out trials on new techniques developed in New Zealand and the Netherlands and modified them for use at home.
A decade ago a decision was made to use "innovation and technology transfer to improve the position of Irish producers", says Donal Maguire, the aquaculture development manager at BIM.
Changes introduced in the way mussels are grown and harvested has improved the competitive position of Irish mussel producers by 20-25 per cent, says Maguire. What has caused this improvement?
Maguire says that three related changes have made a difference to the quality and price of the vacuum-packed mussels that you buy at the supermarket. One is a more eco-friendly method of cultivation, another is easier handling methods for adult mussels, and finally, the use of a new harvesting pump, something that has increased the yield.
Traditionally, mussels are grown in two ways, which have differing results. "Bottom culture" involves dredging of mussels from naturally occurring seed beds (mainly off the east coast) and then growing this seed in managed pots.
"Rope culture" involves collection of the juvenile mussel seed, known as "spat", and growing it within a mesh before harvesting after about 18 months. This mussel is thinner-shelled and generally cleaner than the bottom variety and is ideal for the processed vacuum-packing market, he says.
BIM then started looking at a new technique developed in New Zealand, which is based on using a continuous run of recyclable rope.
Whereas traditional rope cultivation uses a nylon mesh known as "pergolari", the New Zealand method employs a biodegradable rope that rots away into the sea very easily after use.
The pergolari method requires multiple separate ropes that need to be processed individually, and so it "doesn't lend itself to efficient mechanisation and harvesting", says Maguire.
The new technique provided more than a 35 per cent improvement in yield, the BIM trials found. And it has since improved further on yields by developing a new method for harvesting the mussels off the rope.
The traditional approach was to pull the ropes out of the water and then detach them, a method that can result in a proportion of the yield falling off or being broken.
To counter this wastage, BIM has adopted the use of a "venturi pump", which was originally designed in the Netherlands. This system uses centrifugal suction of mussels off the rope while still in the water.
This new system is now being used in counties Cork and Kerry in the south-west, Galway and Mayo in the west, and Donegal in the north-west.
• Ashok Jansari is based at the University of East London and is on placement at The Irish Timesas a British Association for the Advancement of Science Media Fellow