This work package aims to define the habitats used by outward migrating salmon and resident marine phase sea trout through a network of moored acoustic receivers.
The critical issue for both species is population decline, without full knowledge of cause. These species are closely related and are present for some of their lifecycle in the same rivers and coastal waters, but there is an emerging need for very different population management strategies due to differing life history strategies and ranges used in the marine environment.
Separation of legislative provisions for the two species which have been closely linked in the UK and Ireland for almost a century is now an obvious management objective.
This project proposes to make the first check for success of migration on leaving rivers and close to coasts before movement of the fish into the open ocean.
It will shed light on causes of potential mortality – whether linked to human activity, predation, or environmental conditions. Additionally, by determining the length of time the fish track the coast before moving offshore this project can inform decisions on the usefulness of looking further out to sea in future projects.
The COMPASS project will set up a network of receiving recorder stations spanning the border in the North East of Ireland, on the coasts of from County Louth, through Carlingford and Counties Down and Antrim. This work package proposes to establish a nearshore ‘loose’ array along the coast extending from Larne on the north east coast to the Boyne estuary (located south of Dundalk Bay). The array will be punctuated by several different arrangements of receivers which will provide intensive coverage in key areas along the loose array.
The COMPASS project approach is mindful of the small size of salmon smolts, which require small tags, and maximises the prospects of multiple detection when passing within the range of the acoustic arrays. Only wild salmon smolts will be tagged which should offer better insight into juvenile wild salmon behaviour rather than reared smolts which are commonly used in similar studies. Salmon smolts can be caught with a variety of benign techniques, including electrofishing, screw traps and skilled rod and line fishing.
Combining tag pop-up location with the tag temperature data and combining with environmental data output from the COMPASS network of buoys and other monitoring networks will provide data to allow preliminary investigation of the likely migration route of these fish.
Acoustic tagging of salmon and sea trout will provide information on their movement as they pass within the range of a network of receivers deployed at intervals along the nearshore coastline. Standard tags will provide these data which will be supplemented by acoustic tags with temperature recording capacity to determine the marine layer in which these fish were utilising.