ONE OF the last trout lakes in Ireland free from zebra mussels has at last been conquered by the invasive species.
The Western Regional Fisheries Board has confirmed the presence of the marine pest on the 22,000 acre Lough Mask in Co Mayo.
The board has now urged appropriate measures by anglers – such as the sterilising of boats before they are transferred from Lough Mask to other waterways which are uncontaminated by the mussels.
Zebra mussels, which are native to rivers entering the Black Sea and the Caspian Sea, are thumbnail-sized shellfish that consume the plankton on which small fish depend. As well as ecological damage, they create problems for boat owners and can clog water pipes.
They were first recorded in Ireland in 1993, when it is believed they arrived on boats from England or the Netherlands.
They quickly spread throughout the Shannon system and were discovered some years ago in Lough Gill and Lough Arrow in Co Sligo before being detected more recently in Lough Conn (Mayo) and Ross Lake, a Connemara lake which feeds into Lough Corrib.
Kevin Crowley of the fisheries board said that infestation affects the ecology of a water body as well as the food chain with long-term implications for fish stocks.
The priority now was to prevent the spread of the mussels to other trout lakes in the region such as Lough Carra, Mr Crowley said. Lough Mask hosts the prestigious World Cup Trout Fly Angling competition every summer.
Washing facilities for the cleaning of boats prior to their removal from Lough Mask have been installed at Cushlough Pier.
Denis Kelleher, public relations officer of the world trout fly angling competition, said the contamination of the lake was “unwelcome” and would possibly have detrimental effects on fish stocks in the lake in years to come.
Lough Mask is the source of drinking water for Castlebar and large parts of south Mayo but assurances have been given that water quality won’t be affected by the mussels.
A danger exists, however, that the out-take pipe from the lake may become encrusted with mussels, leading to higher maintenance costs for Mayo County Council.
The mussels carpet lake shorelines, reducing ground conditions to an unpleasant, uneven surface.