FEMAR

Fine-Scale Fish Movement
Tracking Relative to Habitat:

Knowledge of the movements of marine organisms is extremely limited. Older fish tracking techniques and technologies cannot provide the detail and spatial resolution required to effectively manage today's increasingly overpressured fisheries. Passive underwater listening devices employing hydroacoustic technology have become increasingly popular due to their relative ease of deployment and their ability to provide a long-time series of moderately precise movement fixes (400 to 1500 m resolution). Radio-acoustic positioning technology is able to provide far more precise position fixes (1-2 m resolution) in "real-time" and is capable of addressing a variety of management issues, including fish home range size and shape, locations of preferred sites/essential fish habitat, speed of movement, and flux/advection rates between areas. The VEMCO VRAP system is a commercially-available radio acoustic positioning system consisting of three buoys, each containing a hydrophone, receiver, and two-way radio link, configured in an equilateral triangle over the reef. A base station consisting of a personal computer with a two-way radio, antenna, and an interface box receives radio signals via UHF from the buoys and delivers them to the PC every time a pulse signal is detected. The origin point of the pulse is determined by triangulation of signal arrival times at the three buoys. Organisms may be tracked continuously across an area of approximately 54,100 m2. Depending on environmental conditions, the VRAP system is typically able to furnish the position of a tagged individual at a resolution in the range of 1 to 2 meters within the buoy triangle. Although the VRAP system has great potential, it is subject to a variety of limitations and tradeoffs which should be considered before embarking on any field study. A current field experience involving the utilization of VRAP to track bonefish (Albula vulpes) and gray snapper (Lutjanus griseus) movements in a coastal marine setting is discussed. -Nick Farmer

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