IMIS

To aid in the protection and conservation of a species it is important to define their spatial, temporal and behavioural characteristics throughout their lifecycle. This is especially true for species with a wide variability in habitats and feeding strategies in their lifecycle. Atlantic salmon (Salmo salar) are an anadromous fish species spending part of their early life in freshwater and then adapting to move into the marine environment to mature fully into breeding adults, eventually returning to their natal rivers to spawn. The routes they take to get to the marine environment have not been described in great detail. These routes can be significant areas of conservation concern for this species, as any interruption of this migration into the marine environment could result in less fish returning to the natal rivers in future to spawn and the potential collapse of the population. The aim of this study is to define, in high resolution, the routes taken by this species from the north west of Ireland to the marine habitats in the North Atlantic. This part of the project will run from 2020-2024 and will tag around 100 salmon smolt from the river Bush each year with acoustic V7 tags. These tags are a mix of short- and long-life tags; short-life to operate for the smolt outrun only and long-life – programmed to turn off after going to sea and then turn on again in 2021 in time - for the return from sea. This second class of tags will help to fulfil the objective to assess the potential for programmed acoustic tags to provide supplementary information on longer term survival prospects of Atlantic salmon. Acoustic telemetry will be used to monitor survival of Atlantic salmon smolts as they travel out from the Bush and into coastal marine waters. An array consisting of both VR2Ws (in the lower Bush) and VR2ARs (in nearshore coastal waters) will be deployed to track the movements of tagged fish. As the smolts move into deeper offshore waters they will be detected via the new SeaMonitor Malin-Islay receiver line. These same arrays will detect the returning salmon with long-life tags. The SeaMonitor acoustic telemetry data generated in this study will be compared against the independent marine survival estimates for individual smolt cohorts assessed through historic and ongoing trapping work at Bushmills. There is also the potential of the marine array to record fish from other rivers which have also been acoustically tagged, and other species which are not the target of this study. Results from this study will be used to make recommendations for salmon management in this area.