Salmonid Habitat Assessment

Salmonids of Irish rivers (salmon and trout) have specific habitat requirements when it comes to spawning, nursery and juvenile habitats. Salmonid Habitat Assessment allows a stretch of river or stream to be assessed for its likely ability to support salmonids at various life-stages.  This, combined with consultation with Inland Fisheries Ireland, may allow the avoidance of using potentially destructive methods such as electro-fishing.

The salmonid life-cycle is more complicated than many other species. Spawning occurs in areas of gravel and cobble, often in headwater streams, where the adult female constructs a nest called a ‘redd’ out of gravel and cobble into which the eggs are laid. The male then fertilises the eggs and they develop within the gravel mound. At this life stage, suitable, clean spawning gravels are high dissolved oxygen levels are vital to the survival to the eggs to hatching.

The eggs hatch into alevins, which still have a yolk sac attached and remain within the gravel. As they develop further, they become fry and begin feeding. As the fry grow, they become parr becoming more territorial and feeding mainly on freshwater macroinvertebrates. After a number of years, salmon and sea trout parr transform into smolts in preparation for migrating to sea, where the adults do most of their growing before returning to their natal river to spawn.

BEC Consultants can carry out Salmonid Habitat Assessments of rivers and streams close to proposed developments to assess the likely importance of the watercourse to salmonids at various life stages.