The pollution caused the death of brown trout and migratory sea trout in the river. Many migratory fish, such as trout and salmon, swim up smaller tributaries to lay eggs in cleaner, gravel-bottomed or cooler waters away from larger predators in the main river.
The club hopes forthcoming investigations will establish the cause of the latest incident and help ensure appropriate steps are taken to protect the river and its wildlife.
The club has encouraged local representatives and authorities to continue to prioritise rivers and to direct resources towards improving water quality and preventing further incidents.
Generations of fish were wiped out. Resident fish and non-resident migratory fish that return at this time of year to spawn were affected.
A tributary is a smaller river that flows into a larger mainstem river. Migratory fish often use those waters to spawn.
McKibbin said the incident was soul-destroying for members and volunteers who work to improve the river, particularly as it was still recovering from major pollution incidents and fish kills in 2013 and 2015. Authorities said the incident was reported by a member of the public. Investigations into the cause were expected to follow.
The club said it wanted the river and its wildlife protected after repeated fish kills. He said paltry fines that usually follow incidents of this nature are not a deterrent and the current system is broken.