Migration of Atlantic salmon (Salmo salar) smolts and post-smolts from a Scottish east coast river

• Main Author: Main, Robert Andrew Kenneth
• Format: Thesis
• Language: English
• Published: 2021
• Subjects: QH301 Biology; QL Zoology; Dee; Atlantic salmon; Salmo salar
• Online Access: http://theses.gla.ac.uk/82089/; https://theses.gla.ac.uk/82089/13/2021MainMScR.pdf

The near-shore migratory behaviour of Atlantic salmon (Salmo salar, Linnaeus 1758) migrating to sea for the first time is poorly understood. This study aims to assess whether salmon smolt survival is consistent along the River Dee in Aberdeenshire, through Aberdeen harbour and early in their marine migration out to ten kilometres from shore. This study also looks at the patterns of directional movement in the sea during the first 10 km of post-smolt migration to distant feeding grounds and provides estimates of missed detections based on range testing and simulation results. One hundred and sixty wild salmon smolts were implanted with acoustic transmitters (tags) in three tributaries of the Aberdeenshire Dee in 2017 (n=60) and 2018 (n=100). Several tags each year were capable of transmitting temperature and depth (2017 n=15, 2018 n =40) readings. These temperature depth tags were used as a proxy for predation. Smolt progress down river and out to sea was monitored remotely by a large array of Acoustic Listening Stations (ALSs), moored in the river (individual receivers), harbour and marine environment (gates of ALSs). One marine gate (IN), consisting of 35 receivers was deployed in 2017, four kilometres from the mouth of Aberdeen Harbour. In 2018, a second marine gate (OUT) was added, consisting of 98 additional receivers 10 km from the mouth of Aberdeen Harbour. In addition, an Acoustic Doppler Current Profiler (ADCP) was deployed in 2018, to measure marine currents allowing for determination of the actual swimming vectors taken and speeds of post-smolts at sea. Using detections as a proxy for survival and lack of detection as a proxy for mortality (this must be treated with some caution as some tags may not be in the original study animal and might still be counted as surviving or fish passing a receiver without being detected, tag failure or tag ejection might account for some of the presumed mortality); mortality was different in Aberdeen Harbour and in early marine migration between years. The upper river ...