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 20 cm s-1-110 cm 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 7.85 cm s-1 (std. dev. 7.5 cm s-1). The study thus demonstrates the feasibility of measuring the swimming speeds of individual free-ranging fish using this method.