A New Method for Measuring Free-Ranging Fish Swimming Speed in Commercial Marine Farms Using Doppler Principle

A novel Doppler shift based technique for measurement of free-swimming fish speed in marine farms using acoustic telemetry tags was developed and evaluated in this study. The proposed method can potentially augment current telemetry systems with a new biologically relevant measurement without significantly changing the size and energy constrained tag-side of the telemetry systems. For speeds in the range of 20cm s
^-1
-110cm s
^-1
an overall relative rms error of less than 10% in measured speed based on the proposed Doppler method was achieved in the tests conducted at a fully stocked commercial fish cage, with an rms error of 7.85cm s
^-1
(std. dev. 7.5cm s
^-1
). The study thus demonstrates the feasibility of measuring the swimming speeds of individual free-ranging fish using this method.