Reported by BBC Science
The angling club said that the pollution incident killed brown and migratory sea trout
A investigation is underway after "a major fish kill" in a County Down river, the Department for Agriculture, Environment and Rural Affairs (Daera) has confirmed.
The pollution caused the death of brown and migratory sea trout in the Gransha, Ballystockart and Inler Rivers.
More from the original report
Glenn McKibbin, the secretary of Inler Angling Club, said about 1,000 fish were killed in the incident and it "could not have happened in a worse location on the river or at a worse time".
Daera said they are working with the NI Environment Agency to "identify the source of the pollution and to finalise the numbers of fish killed".
The Department said the incident was reported by a member of the public on Tuesday at 09:30 GMT.
McKibbin said that "current and future fish stocks obliterated for years to come".
He added that resident and non-resident migratory fish, which only return at this of year to spawn, have been impacted.
"Knock-on effects for other wildlife such as resident kingfishers, herons & otters unavoidable.
"For our members and volunteers who work tirelessly in a bid to improve the river this is soul-destroying, particularly as the river was still in recovery from major pollution incidents / fish kills in 2013 and 2015," McKibbin said.
"Waterways up and down the country continue to be treated like sewers.
"The paltry fines that usually follow incidents of this nature are not a deterrent and the current 'system' is broken."
The club said that the fish killing impacts resident kingfishers, herons and otters
Many migratory fish, such as trout and salmon, swim up smaller tributaries to lay their eggs in cleaner, gravel-bottomed, or cooler waters away from larger predators in the main river.
A tributary is a smaller river that flows into a larger mainstem river where many migratory fish, such as trout and salmon, swim up to lay their eggs away from larger predators in the main river.
Inler Angling Club Chairperson David Pyper said: "For those who dedicate so much time and effort to caring for…