An Asian clam found in Lough Derg
The water quality of Lough Derg is poor but the lake still supports a healthy stock of trout, local anglers have been told.
The comments came at a meeting to outline the findings of the Lough Derg Native Fish Biodiversity Project, which has been ongoing since 2006 when anglers noticed a fall in trout numbers.
Joe O'Donoghue, chair of Lough Derg Angerls Association, which comprises 13 clubs, described the work as an “example of citizen science”, with anglers catching, photographing and measuring fish taken from the lake.
As well as looking at trout, the project is also examining other species, including the lamprey.
Dr Fran Igoe of the project acknowledged the work being done by anglers and revealed that 22 species had now been identified in Lough Derg.
“People are becoming more aware of the lake for tourism and conservation,” he said, pointing out that there were potential conflicts from the hydroelectric dam, boating, non-native shrimps and the zebra mussel.
He said the core aim was to describe and identify native fish biodiversity and ask if the croneen trout used the lake to feed, did it still contain gilleroo trout, and if the Irish pollan was still in Lough Derg?
The latter sustained a commerical industry at one stage and the answer was that pollan are still in Lough Derg.
One of the other interesting revelations was that lamprey in the lake were sea lamprey and were not land locked. The project has found no adult lamprey, which points to them coming up through the dam to feed and spawn and then heading back to sea.
“They attack bream and roach but don't appear to impact on trout,” he said.
However, Dr Igoe said that putting the lake in context, the water quality of it was poor and its tributieries was not good.
“You have a really special lake here,” he said.
Threats to the lake were identified by Dan Minchin of the Lough Derg Science Group, who said that invasive shrimp populations were colonising the lake.
“The Asian clam was first found in 2007 and is now at Parker's Point. I have no doubt it will be found in Ballina within the next decade,” he said.
Other threats come from the bloody-red shrimp, the Black Sea shrimp and the killer shrimp, the latter which feeds on mayfly larvae and this could threaten the trout population. The bloody-red shrimp is a threat to the native Irish shrimp in Lough Derg.
Dr Minchin pointed out that the invasive species were coming in on hulls from boats brought over from the UK for use on the lake.
Prof Paolo Prodohl of Queens University Belfast, who is carrying out a genetic analysis of the lake's trout, said that there was some work to do but the lake's trout will survive.
While there was considerable socioeconomic value from the lake through angling tourism, there were also threats from human activity through urban growth, farming practices, water abstraction, arterial drainage, weirs and the hydroelectric dam.
With over €300,000 spent on the project since it began in 2006 and over 4,000 trout analysed, Prof Prodohl concluded that Lough Derg had a healthy trout stock, with 40 populations of trout in the lake and its river systems.
Some of the phylogenetics analysis had shown some trout carried DNA going back to when the trout first arrived after the last Ice age.
The Lough Derg Native Fish Biodiversity Project is being led by Lough Derg Anglers Association, the Irish Char Conservation Group, Queens University Belfast, Prof Mike Power at Waterloo University in Canada, Inland Fisheries Ireland, the Environmental Protection Agency, the Heritage Council, Tipperary LEADER, Galway LEADER.
For more details or to get involved in the project, log on to www.char.ie or contact Dr Fran Igoe at email@example.com