Appraisal of Fish Behavior by Analyzing their Dynamics

We present an advanced system for monitoring the behavior of a fish population in an experimental tank and derive a set of characteristic features pertaining to their dynamics. Using a 3-D array of ultrasound transducers, the system provides time series of fish positions, allowing for assessment of the dynamics of both the geometric centre (centroid) and the mean spatial extension of the fish population. We reveal that evolution of the mean spatial extension of fish population and the related standard deviation represents a sensitive indicator of fish behavior in respect to the quality of the aquatic environment. Emphasis has been given to reversible effects i.e. whenever water parameters returned to normal (physiological) levels, fish behavior exhibits similar dynamical features. Whereas fish behavior was previously assessed by several monitoring techniques (e.g. electrical impedance, video recording, hydro-acoustics etc.), this study reveals the advantages of using ultrasounds to continuously monitor the three-dimensional position of fish, having also the quality of being independent on water turbidity or light intensity.