Canoeists enjoy running rivers in the winter months. Whilst keen to see sustainable use of waterways, the Loughs Agency urges paddlers to avoid trampling across gravel at this time as fish eggs are likely to lie in voids within the material (the Agency is charged with management and conservation of the fisheries of the Foyle and Carlingford catchments).
Salmon and trout deposit their eggs (“spawning”) in the gravel of swift flowing rivers and streams from November to January. In spawning, the fish make “nests” (or “redds”) in the gravel using their tails. Redds form an elliptical profile, with a hollow (or “pot”) upstream of a slightly raised tail, formed from excavated material. The eggs take many weeks to mature, meaning that delicate salmon and trout eggs and fry are likely to be within the gravel from November to May.
Trout will redd in gravel from 4mm to 65mm in diameter while salmon can redd in gravel 30mm-80mm in diameter. Although the eggs are usually deposited some distance below the surface, they remain susceptible to damage due to compaction and siltation (due to people walking on the redd material, for instance), processes that cause a reduction in permeability of the redd material and, hence, suffocation of the eggs due to reduction in the amount of oxygenated water running by.
Disturbance of river gravel is likely to have a detrimental effect on populations of salmon, sea trout and brown trout and the ecology of the river as a whole.
For further information please contact the Loughs Agency on: 028 7134 2100.