Investigating how trawlers affect seabed

Does trawling damage life on the seabed? Recent research suggests that the jury is still out on this, but now the Martin Ryan Marine Science Institute at NUI Galway aims to tackle the issue. It is to lead a £1 million multinational programme on the impact of demersal trawls on benthic or bottom-dwelling beasties.

The £1 million European-funded programme will involve teams from Ireland, Holland, Belgium and Germany, and have promised to work in consultation with the marine industry. The aim is to modify gear and net design to develop environmental-friendly fishing techniques.

Recent European-based studies have indicated that commercial trawling tends to disturb organisms that dwell in or on the seabed. Benthic organisms live on, near or in the sediments of the sea and range from bacteria, unicellular algae and protists of less than 0.1 millimetre in diameter to small worms and snails, sea urchins and bottom-dwelling fish.

These animals are often consumed by scavengers and predators rather than by targeted fish species. The theory is that reducing disturbance could increase food availability for species higher up the chain and also reduce discards of benthic beasties from the net.

The programme - some £300,000 of which is coming to NUI Galway - comes as a bit of a birthday present for the Benthos Research Group, based at the university's zoology department. The group is celebrating its 25th birthday under its founder, Prof Brendan Keegan. This latest contract brings its research earnings to more than £3 million. Recently, colleagues in the Martin Ryan Institute also secured a £500,000 international contract for satellite studies of fish stocks.

The Benthos group scientists will concentrate on otter trawls - large conical nets, the mouths of which are held open horizontally by the spreading force of trawl doors or otter boards. This work will be conducted in association with colleagues from the Marine Institute in Dublin. The Dutch, Belgian and German partners will focus on modifications to beam trawls - held open horizontally by a fixed boom or spar - in the North Sea.

Prof Keegan says that close co-operation with the industry is essential if the project is to work. "Driven by the requirement that commercial catch levels be maintained with emergent new gear designs, alternative techniques must be effective in reducing the level of discards," he said. Dr Brian Munday, a senior member of the Galway group, will co-ordinate the programme, and the first meeting of participating institutes will be held in NUI Galway on February 12th and 13th.

The Benthos Research Group recently succeeded in securing several contracts, valued at about £80,000, under the Marine Institute's Operational Programme for Fisheries Research. One of these contracts will investigate discards of benthic animals by the Irish whitefish fleet, and will be carried out in conjunction with existing programmes run by the Fisheries Research Centre at Abbotstown, Dublin. A parallel study, which is being conducted with the Foyle Fishermen's Co-op in Greencastle, Co Donegal, will determine survival estimates for selected bottom-living animals.

The Benthos Research Group has already pioneered the development of sediment profile imagery in European marine research. Cameras arranged as an inverted periscope take photographs within the soft seafloor area. These images are then analysed by computer to determine information on the seafloor's state of health.

Under Dr Anthony Grehan, researchers are currently using these techniques on a number of EU-funded programmes in the North Atlantic and Mediterranean. A new EU contract should result in the group's imaging devices being used on underwater remotely operated vehicles or ROVs. And the technique may have a direct application to the trawling research programme. A profiling camera incorporated into an "underwater plough" may be able to assist in visual assessment of a trawl's impact on the seabed.