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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.

A novel Doppler based speed measurement technique for free-ranging acoustically tagged fish was developed and validated through a field experiment in a marine aquaculture farm. For emulated swimming speeds in the range 25 cm s −1-60 cm s −1 , an rms error of 5 cm s −1 with a standard deviation of 4.7 cm s −1 was achieved, and with a relative error typically less than 10% of measured speed. The technique is designed to integrate easily with existing acoustic fish telemetry systems and requires only three hydrophones to determine swimming speeds. Measurement of fish swimming speed has a wide range of applications within fisheries sciences and may become a valuable tool for assessing fish behavior and performance in marine farms.

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