VEMCO receivers have been externally mounted and Lotek hydrophones integrated into a propeller-driven REMUS-100 AUV. Lotek stereo-hydrophone acoustic receiver systems have been integrated into propelled OceanServer IVER2 AUVs to track and follow leopard sharks. For example, buoyancy-driven Slocum gliders with integrated VEMCO cabled receivers (VR2c) or externally mounted mobile transceivers (VMTs) have been used to study sturgeon and shark habitats. Īutonomous underwater vehicles (AUVs) or platforms are becoming more common telemetry assets because receivers can be self-contained and externally attached, or integrated for real-time detection while simultaneously measuring physical and biological ocean properties. With technological advances, there are a number of marine vehicles that are capable of tracking animals or detecting their presence, but in many cases, proper validation (e.g., range detection testing) is needed to interpret the acoustic data, to establish the utility of the method and to develop effective sampling plans. However, records of animal locations are limited to areas that have receivers, typically shallow continental shelves, which often leave large gaps in our understanding of animal movements due to limited data coverage. Information attained from passive telemetry studies provides insights far beyond what can be observed by eye, video or active tracking and is a critical component to conservation and management efforts. Animals can be tagged with acoustic transmitters and their movements monitored by coastal arrays of stationary hydrophones or acoustic receivers. Studies of the long-term temporal and spatial ecology and behavior of marine organisms have been augmented by acoustic telemetry. Wave Gliders equipped with receivers can provide useful data and can be an effective biotelemetry asset that could supplement stationary arrays of acoustic receivers or act as an exploratory technology to search for biologically important areas. Wind speed, water temperature, mooring line tilt angle and vehicle dynamics were found not to be as important over the limited range of conditions over which our study was conducted. Distance between the receiver and transmitter was the main factor affecting detection probability, with background noise, receiver heading, angle between transmitter and receiver and wave height also being important.
The higher power output transmitters had a 20% detection efficiency to ranges of ~ 0.5 km (153 dB) and ~ 0.8 km (160 dB). The forward-facing receiver had almost half the detection efficiency of the backward-facing transceiver, suggesting a backward configuration is optimal to reduce the influence of the moving platform. Resultsĭuring our study, the sea state was mild with low wind speeds ( 0.5 km and the maximum range was 0.5–1.2 km. Surveys were conducted around two stationary moorings equipped with receivers, transceivers or tags emitting signals with different power outputs.
Here, we report on the deployment of a wave powered unmanned surface vessel, the Liquid Robotics Wave Glider SV3, equipped with a forward- and backward-facing acoustic receiver (VR2W) and transceiver (VR2Tx) at 4 m depth. To assess the effectiveness of these emerging platforms, proper validation and range detection studies are necessary. However, mobile autonomous platforms are becoming important tools that support the science of understanding biophysical relationships because they can concurrently detect tagged individuals and measure properties of their ocean habitat.
Detecting tagged animals in coastal environments is often limited to stationary arrays of acoustic receivers that can decode transmissions from tags on animals.
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