Rollerball shows how to cut seabed damage

A new rollerball system designed in Howth, Co Dublin, and tested by an Aran Island skipper, could solve environmental problems associated with trawling, according to an NUI Galway research team.

The new system allows a trawl to move over, rather than through, the seabed to protect invertebrates, while catching the same amount of fish. It also reduces fuel consumption. Initial trials have proved to be "very promising", Dr Brendan Ball of NUI Galway's Martin Ryan Marine Science Institute told a seminar hosted by the Royal Dublin Society and the Marine Institute yesterday.

The initiative was taken as part of a 1.2 million euro project funded by the EU, to deal with the impact of trawling on the seabed. It is being led in Ireland by scientists from the Department of Zoology Benthos Research Group and the Marine Fisheries Environment Unit of the Martin Ryan Marine Science Institute in NUI Galway.

Appropriately entitled Reduce (Reduction of Environmental Impact of Demersal Trawls), the project here has concentrated on the effects of otter trawls, working in co-operation with the fishing industry and the Marine Institute. Otter trawls have a less harmful impact than beam trawls, particularly on soft ground, but reducing their contact with the seabed is regarded as a priority.

The designer of the new system was Mr James McDonnell of Gear Tech Ltd in Howth. He fitted swivelled rollerballs along the wings of a 40-fathom dual-purpose prawn trawl. The rollerballs can be changed and modified on deck as required. Sea trials were carried out from the 75-foot trawler Hercules II, owned by Mr Padraigh Dirrane of the Aran Islands, in September last year and May this year.

Dr Ball told the RDS/Marine Institute seminar that the rollerball design recorded an equivalent commercial catch of black sole, ray, skate and prawns to that of a standard trawl. There was no difference in fish discards, but there was a 35 percent reduction in invertebrate discards. Catch of debris was also low, at less than 5 per cent.

Skipper Dirrane also reported a reduction in fuel consumption. He worked at 2.6 knots at 850 r.p.m. with a two-inch standard footrope, but this was reduced to 700/750 r.p.m. at the same speed with the rollerball net. The skipper told the scientists he had been sceptical of the idea at first, but had no major difficulties in handling the gear or in shooting and hauling.

The Reduce project is due to finish next month but Dr Ball said he hoped further EU funding could be obtained to continue the work. In the meantime, preliminary results will be given to the fishing industry and the scientific community.

The seminar, "Science in the Service of the Fishing Industry", was hosted by the Royal Dublin Society in association with the Marine Institute to mark the centenary of Government fisheries research in Ireland.