Receivers ready for deployment

Receivers

Acoustic receivers detect the presence of acoustic tags attached to, or implanted within, marine animals. These receivers are placed in a series of lines on the seabed. Each receiver in a line is spaced at a predetermined distance in order to maximise the probability that a tagged fish will be detected

The lines are long enough to form a complete curtain across a migration corridor and are strategically placed in series along the corridor in order to satisfy the project goals. Once a receiver detects a tag, it checks the tag’s validity and logs the tag’s serial number, the date, time, and any additional information transmitted by the tag. Data is periodically uploaded from the receivers using a wireless link to a nearby boat. Survival and movement patterns of individual animals can be reconstructed using the time of detection on different acoustic lines.

To date, the POST acoustic array has been primarily designed to monitor the survival, direction, and rate of migration of Pacific salmon smolts after leaving freshwater systems. For this purpose, multiple lines of receivers that span the width of the Pacific continental shelf of North America have been placed along potential migration routes over an 1,800 km section of the coast between Cascade Head, Oregon, and Icy Strait, Alaska (link to array location figure).

Various receiver designs are in use.

POST uses an array of both VR2 and VR3 receivers manufactured by VEMCO. VR2s must be physically recovered to access the data and are chiefly used in temporary deployments. VR3s operate on battery packs that last 4-7 years (depending on the programming) and are designed to remain permanently on the seafloor while allowing remote data upload. Future generations of receivers may host of a wide suite of oceanographic sensors in addition to the fish tracking modules. When complete, these sensors will provide a detailed, continuous system to monitor how the ocean off the west coast of North America changes over time and how the fish respond within this environment.