Salmon return to the Tolka River after 100 years
Published 28/09/2011 | 05:00
SALMON have returned to the once heavily polluted Tolka River in Dublin for the first time in more than 100 years.
Falling pollution levels, modifications to weirs, and successful breeding by the elusive 'king of fish' mean the capital now has three rivers producing wild stocks.
Dr Ciaran Byrne, chief executive of Inland Fisheries Ireland, said Dublin should be proud of the wildlife revival.
"Up to the year 2000, Dublin and Reykjavik were the only two capital cities in Europe which had wild Atlantic salmon stock in a river within city boundaries," he said.
"Now Dublin can boast about having three salmon rivers within its boundaries -- the Liffey, Dodder and now the Tolka. In environmental terms, this is an important step forward."
Inland Fisheries Ireland said that fish surveys in the Tolka had indicated the presence of juvenile wild Atlantic salmon in three river locations in the Glasnevin and Finglas areas. Adult fish were also being counted in the Glasnevin area.
It was the first record of wild salmon reproducing in the Tolka for at least a century, the authority said.
Dr Byrne said the recolonisation of the river was undoubtedly linked to reduced pollution levels.
Flood relief works have also helped -- with the removal or modification of a significant number of man-made weirs opening up the river system to migratory fish.
After work on the Tolka was completed adult sea trout immediately ran the system all the way upstream to its headwaters in Dunboyne, Co Meath, for the first time in at least 150 years.
A study in 2005 found the Tolka was incapable of supporting life because it was so polluted with chemicals.
The Trinity College study found the inner basin of the river had the highest concentration of pollutants in north Dublin Bay with levels of lead, phosphorus and nitrogen so high in one stretch, from Clontarf up to Bull Bridge and Dollymount Strand, that fish and plants could not survive.
Successful river rehabilitation schemes elsewhere in Europe have seen salmon return to the Seine in Paris and the Rhine in Germany, and brown trout to the Wandle in London.