Anglers have lodged a complaint with Europe over an exemption that allows Northern Irish farmers to spread slurry on their land during the winter closed season.
Angling body Fish Legal lodged the complaint with the European Commission on behalf of Ballynure Angling Club over the exemption, or derogation, which it says has been introduced by the Department of the Environment (DoE) for the past two winters.
Under the Nitrates Directive, farmers are required to protect waterways from pollution by not spreading slurry on their land in winter. But for the last two years the DoE has allowed farmers to spread slurry during the closed season.
However, the DoE insists it has not introduced a relaxation of the rules, but simply drawn farmers' attention to the 'reasonable excuse' defence, which allows farmers to spread slurry in the closed season if poor weather has prevented slurry-spreading during the open season.Fish Legal said: "The closed season was imposed under the Nitrates Directive to protect Lough Neagh from hypereutrophication (high nutrient levels). The relaxation of the closed season presents a serious threat to water quality."
If Northern Ireland is found to have breached the Nitrates Directive, it could face infraction fines amounting to millions, according to Robbie Marshall, a committee member with Ballynure Angling Club.
He added that the pollution would "destroy fish and plant life" in Lough Neagh.
Mr Marshall said the onus is supposed to be on farmers to have tried all reasonable options before spreading slurry in the closed season, but in reality it appears that the system has very few checks.
"We believe this is a breach of the Nitrates Directive and that is why a letter of complaint will go to Brussels," he said.
A DoE spokesman said: "It is important to clarify that there has not been any derogation from the slurry spreading closed period over the past two winters," adding that the reasonable excuses defence was contained in the Nitrates Action Programme Regulations (NI).
"The indication is that the measures introduced in agriculture to manage farm nutrients are beginning to show improvements in the status of our water environment," the spokesperson added.
Lough Neagh is the biggest freshwater lough in the UK and Ireland and is home to unique dollaghan trout, found nowhere else in the world. The dollaghan run the Lough Neagh tributaries to spawn from June until November, but are under serious threat due to many factors, including illegal netting on Lough Neagh. Every year, the Ballinderry Fish Hatchery rears around 1.5 million native dollaghan trout to rebuild numbers in the Lough Neagh system.