An eel fisher is to argue at the high court in Belfast that the authorities have allowed the ecological collapse of Lough Neagh by failing to take action over pollution.

Declan Conlon, whose family have for generations fished the inland lake in Northern Ireland that once hosted the largest wild eel fishery in Europe, is seeking to take a judicial review against the Department of Agriculture, Environment and Rural Affairs (Daera). He will argue the department has failed to act against polluters despite clear evidence of the ecological collapse of the lake.

Lough Neagh, the UK’s largest lake by surface area, is situated in the heart of Northern Ireland and is a globally important and internationally protected site. But it is suffering from an acute environmental crisis. It is overloaded with phosphorus and nitrogen from agriculture, including farm runoff, fertilisers and animal waste, as well as from inadequate wastewater treatment facilities and septic tank leakage.

The lake’s once clear, light brown waters are now green from recurrent algal blooms, which deprive the lake of oxygen and choke aquatic life. According to Friends of the Earth Northern Ireland (FoE NI), the toxins from the algae has killed swans, fish and even pet dogs.

Eel fishing was suspended in 2025 and tourists have fled what should be a freshwater haven for ecological diversity and an abundance of salmon and eels.

Conlon’s livelihood has been hugely affected. He argues in his judicial review that the authorities have continued to rely on on inadequate plans and unenforced pollution regimes despite the crisis facing the lake.

He said he was now watching the lake die in front of his eyes. “My way of life has been destroyed by the blue-green algae and I want Daera to do whatever is necessary to stop the algae and safeguard and protect Lough Neagh, the fish, the flies and the wildlife for the benefit of future generations,” he said. “This isn’t just about my livelihood – it’s about justice for the lough before there’s nothing left for the next generation.”

Enda McGarrity, director at PA Duffy & Co, who are acting for Conlon, said the case reflected the lived experience of those whose livelihoods depend on the health of the lough.

“Where there was once abundance, there are now no flies for the eels to feed on, barely any birds, and stretches of water that smell so foul you cannot stand near them,” said McGarrity.

“Declan did not take this case lightly. He has brought this challenge because he believes the lough, his livelihood, his way of life, and the community that depends on it deserve proper protection under the law.”

FoE NI and River Action are seeking to intervene in the case, which is being heard on Tuesday.

More than 50,000 people have supported FoE NI’s plan to save the lake, which includes bringing it back into community ownership.

River Action’s head of legal, Emma Dearnaley, said the case raised urgent questions about whether enough was being done to tackle the pollution driving the decline of Lough Neagh. “For too long, decision-makers have relied on plans and promises while pollution has continued, and Lough Neagh has visibly deteriorated. We hope this case will help bring about the clear, enforceable action needed to reduce pollution and restore this vital ecosystem.”

A Daera spokesperson said: “Proceedings have now been issued in the matter and it would therefore be inappropriate to comment on the issues before the court.”