Invasive zebra mussels have been found in another seven lakes in Northern Ireland.
The discovery brings the number of lakes or waterways in Northern Ireland known to have been invaded by the damaging alien species to 12.
The latest sites are all satellite lakes around the Erne waterway.
Lough Erne was one of the first to be infected by the mussels and it was inevitable that nearby lakes would eventually succumb.
Zebra mussels can cause the ecology of lakes to change substantially or even collapse.
The mussels out-compete the local swan and duck mussels leading to their extinction.
They also filter the water very effectively, making it so clear that plant growth increases dramatically choking the waterway.
The clear water also encourages toxic algal blooms and whole fish populations can change or even disappear because the mussels have altered the food chain.
The blocking of waterways and the loss of fish can also have a serious effect on tourism.
Another problem is caused by the sheer mass of the zebra mussels.
They can block the pipes of water intakes on boats and shore structures causing machinery failure. The cost of their removal can be considerable and is usually very difficult.
John Early of the Northern Ireland Environment Agency (NIEA) said: "Zebra mussels, which are native to the lakes of south east Russia, can attach themselves to any hard surface such as boats, buoys and water intake pipes, where they can form very dense clusters".
"Zebra mussels have spread to a number of unconnected lakes since their first arrival in the Erne system in the mid 1990s.
"Recent monitoring has confirmed that they are continuing to expand their range I would strongly urge boat owners to clean their boats and equipment to try and prevent further spread."
The NIEA is currently sampling a selection of other satellite lakes of the Erne to find out if they have spread any further. Once the mussels establish themselves in a lake, its almost impossible to remove them.
Lakes invaded by zebra mussels
- Abacon Lough
- Derrymacrow Lough
- Kilturk Lough
- Castle Lough
- Derrykerrib Lough
- Derrysteaton Lough
- Lough Keenaghan
- Lough Erne
- Carron Lough (Derrygonnelly)
- Lough Neagh
- Lough Bresk
- Lower Lough MacNean
By Mike McKimm BBC NI environment correspondent
http://www.bbc.co.uk/news/uk-northern-ireland-15403541
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