The Smolt trap on the River Nairn is gathering very useful information on the productivity of the river. The juvenile salmon in the river are changing to silvery smolts and are modifying internally to adjust to living in saltwater. They travel downstream towards the sea to start the next stage of the salmon life cycle. Before they leave the river, they develop a memory of the odour of their native river so they can return there to spawn after a year or so at sea. The smolt trap catches (without damaging) a sample of juvenile fish each night- the fish travel at night to avoid predators. The smolts and other juvenile fish are counted, measured and a scale sample taken to check their age before being returned safely back to continue their run to sea. Fish scales have growth rings that can be counted to assess the age of fish and the conditions in which they have grown- just like trees.
Source: Findhorn, Nairn and Lossie – Run Smolt Run