Tracking Atlantic Salmon

The environmental research Institute (ERI, Scotland) at the University of the Highland and Islands is monitoring the initial movements of salmon smolts as they leave a number of rivers in the North-East of Scotland and head out to sea. The fish is tagged before they leave the river. After, a network of acoustic listening stations located in estuaries or open sea can log the individual tag number to provide a timed record of the position of individual smolts. These records will be combined with oceanographic models in the area to determine the routes taken by smolts as they move from the river to the sea on the first, critical stage of their northward journey.

The life cycle of the Atlantic salmon encompasses a juvenile feeding migration from the rivers, where they are born, to the rich feeding grounds in the North Atlantic. However, this journey is very risky and energetically very demanding. This is generally associated with numerous fish loses during the early stages of their marine migration.

Although the Atlantic salmon is among the most studied fish species in the world, almost nothing is known about the routes that smolts take in coastal waters when they leave their rivers. This information is particularly relevant as their life cycle is dependent on the completion of this marine journey. Additionally, with the arrival of marine renewables in Scotland this information is vital to inform developers about possible impacts of marine renewables on diadromous fish.

One of the main limitations in the study of salmon at sea has been the difficulties of gathering information using traditional methods (e.g. mark and recapture methods). The recent development of acoustic fish-tags has made it possible to remotely study the behaviour of smolts in the sea. The tags emit pulses of sound and automatic listening stations moored on the sea-bed are used to monitor tagged fish as they pass by. In this case, fish individuals do not need to be recaptured and the data can be accessed upon retrieval of the receivers.

This study is financed by the Flow Country River trust and the Beatrice Offshore Windfarm Ltd BOWL. 

The experimental procedures concur with the national ethical requirements and were approved by Marine Scotland Science.


Project leader Diego Del Villar

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