Pollution dumping or spills have killed fish across Northern Ireland — with waterways often taking years to recover.

Pollutants that get into the water kill fish in two ways: either by directly poisoning them or removing the oxygen they need from the water. But they can also have longer term effects by wiping out the food supplies for young fish.

Major fish kills around Northern Ireland in the past five years include:

River Blackwater, Clogher Co Tyrone, July 2008: Over 100 fish, including trout fry and juvenile salmon killed by pollution.

Ballymoney Burn, Ballymoney, Co Tyrone, July 2008: Around 500 trout killed by suspected sewage spill

Ballymartin River and Sixmilewater, Co Antrim, June 2008: Thousands of game fish and coarse fish die. Pollution suspected.

Cusher River, Tandragee, Co Armagh, June 2008: Hundreds of trout and roach die after pollution released into the river

Lackey River, Co Fermanagh, June 2008: Up to 200 fish, mainly juvenile brown trout, discovered dead. Linked to slurry leak. Fears thousands of young fish |recently released were at risk.

Fardross River, Clogher, Co Tyrone, April 2008: About 900 fish die after farm effluent is discharged.

River Roe, Limavady, Co Londonderry, July 2005: Chemical discharge from factory blamed for fish kill along three kilometre stretch of river.

River Strule, Omagh, August 2004: Fish die in large numbers near sewage treatment works. Fourth major incident in five years.

Inver River, Larne, March 2003: Spill of pig slurry kills thousands of fish. Second time in two years the river was hit.