Tracking array locations

In spring 2015 RS Aqua provided a complete acoustic receiver array to support the long term monitoring of Atlantic salmon smolt during the seasonal migration in the Moray Firth.

The Study

Atlantic salmon populations suffer numerous fish loses associated with the annual migration of smolt from their river nurseries to the feeding grounds of the open ocean. Salmon are a commercially important species yet little is known about the behaviour of smolt and the factors affecting their survival during this risky and energetically demanding journey.

In a bid to better understand the smolt’s migration ecology researchers at the Environmental Research Institute (ERI, Scotland) have deployed an acoustic receiver array, comprised of twenty VEMCO VR2AR receivers and associated moorings, along a 2 km stretch of coastline at the mouth of the River Wick. They are striving to answer questions such as how fast do smolt travel and what routes do they take once in coastal waters? When smolt losses occur are they related to location or varying river conditions? With the arrival of marine renewables in Scotland this information is vital to inform developers about possible impacts of marine renewables on diadromous fish.

Underwater acoustic telemetry has facilitated the 24 hour continuous remote monitoring of smolt in the sea. Salmon smolt are fitted with individually coded 69 kHz VEMCO acoustic transmission tags and re-released into the river. When a tagged smolt comes within range of the VEMCO VR2AR receiver array its presence is detected, timestamped and the tag identified.

The geographical locations of the deployed VR2ARs and their retrieved detection data can be shared with other international aquatic animal tracking networks, such as the Ocean Tracking Network.

The entire VR2AR mooring and floatation system was custom designed and tested by RS Aqua oceanographic engineers. For use in shallow water it was desgined to keep the receiver in a vertical orientation whilst being light weight and easily deployed from a small boat.

VR2AR Shallow Water Mooring


Vemco is the world leader in the design and manufacture of acoustic telemetry equipment used by researchers worldwide to study behaviour and migration patterns of a wide variety of aquatic animals from salmon smolts to great whites. Vemco acoustic transmitters and receivers enable researchers to conduct world class studies in lakes, rivers and oceans that require real-time active tracking; long-time, large scale passive monitoring; fine scale positioning with detailed accuracy; and/or environmental monitoring.