| FISHERIES - MARINE BEHAVIOUR OF SEA TROUT
We inserted two tags in sea trout kelts to help us understand more about their journeys at sea and in estuaries. © Céline Artero/GWCT
Sea trout behaviour in the marine environment BACKGROUND As part of the SAMARCH project, a tracking study aimed at following salmonid migration in estuaries and coastal waters started in October 2017. We are seeking to shed light on the ecology of salmonids in transitional and coastal waters to improve management of Atlantic salmon and sea trout in this habitat.
Figure 1 Daily maximum depth reached by a sea trout from the River Tamar from January to May 2018 based on pressure logged by an implanted tag
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At the end of the calendar year, sea trout come back to the spawning grounds of their natal rivers to reproduce. After spawning the sea trout migrate back downstream to start another marine phase. This provides an opportunity to intercept post-spawning sea trout before they re-enter the sea. During 2017, the pilot phase of this project, we captured 16 sea trout, eight on the River Tamar, three on the River Frome and five on the River Bresle in France. Each of these 16 fish had two tags implanted into their body cavity. The first tag is an acoustic tag that pings every 30 seconds; these pings are detected by acoustic receivers deployed around the studied estuaries. When an acoustically tagged fish is within range of an acoustic receiver, its presence will be detected and the tag ID, date and time is logged. The data downloaded from the receiver network enable us to study the migration timing, speed and mortality of sea trout in transitional waters, an area where they encounter steep gradients in water temperature and salinity. The second tag, a data storage tag (DST), records temperature and pressure every two minutes. As fish are ectothermic (they don’t regulate their internal temperature) the temperature recorded inside the body cavity of the fish reflects the temperature
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30 | GAME & WILDLIFE REVIEW 2018
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www.gwct.org.uk
03/05/2019 14:25:46
