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
Ph: 028 7134 2100.