The Marine Institute says it hopes to identify the cause of the large fish kill at a Donegal salmon farm later this week. Dead fish were still being removed from cages in Inver Bay yesterday.
Institute scientists are seeking international advice on the kill, which is one of the largest to have occurred at a fish farm site in these waters. At least 250,000 fish are estimated to have perished at three farms in Inver Bay, but mortality levels were reported to be falling over the weekend. Fish farmers hope the remaining stock will resume feeding in the next few days.
Scientists are examining six sets of data, said Mr Michael Ó Cinnéide, director of the institute's marine environment and food safety services section. These include fish health reports, phytoplankton data, chemistry, and possible residues in fish, environmental data provided by temperature logs in the bay, the condition of the seabed, and commercial fishing in the area.
The Irish Salmon Growers' Association maintains that dredging or trawling for prawns is responsible, and claims the mortality fall may be linked to the cessation of trawling in the coastal area in the last few days.
It has criticised the absence of a proper State policy on coastal zone management, and says it is angry that the Department of Communications, Marine and Natural Resources should dismiss dredging as the cause, when it had not yet been ruled out by Marine Institute scientists.
"Fish farming and commercial fishing have lived with each other for the last 25 years in Irish waters, and we don't now want to have a row with the fishing industry over this," said Mr Richie Flynn, of the association. "However, fishermen have never been given clear guidelines on activity close to fish farm installations - whereas marine notices are automatically issued when a weather or navigational buoy has been placed or relocated at sea." The association maintains that the fish suffocated when substantial volumes of mud and silt were disturbed by trawling close to the location, releasing hydrogen sulphide. The three fish farms - Ocean Farm, Eany Fish Farm and Creevin Salmon - are still assessing the full extent of the losses. The Northern Regional Fisheries Board says it has not received any reports of fish kills on the Eany system running into Inver Bay, thus ruling out pollution from a freshwater source.
The Federation of Irish Salmon and Seatrout Anglers expressed fears yesterday about the impact on the wild salmon and sea trout fishery running into Donegal Bay, and said it was vital the reason for the kill was established immediately to protect "our already very scarce wild salmonid stock".
The federation renewed its call for an independent inquiry into a fish kill in Inver Bay in June last year, when some 50,000 salmon died during harvesting on the Ocean Farm site. It said local anglers feared that trawling in the area had disturbed these decomposed carcasses which had been "dumped" on the seabed.
Mr Richie Flynn of the salmon growers' association accused the federation of "professional grave dancing". An environmental survey carried out after the kill last year had advised that the carcasses should not be removed, as they would do more damage if attempts were made to remove them. The marine environment was a dynamic living system, and thousands of fish died at sea every day, Mr Flynn said.
Meanwhile, the Department says it has found no evidence to support a reported escape of fish from a farm in the Kenmare River in Co Kerry. The Friends of the Irish Environment had claimed there was such an escape from a farm owned by Murpet Fish, which is now in receivership.