Fish detection using electrical impedance spectroscopy

Fish detection in shallow water conditions or close to the bottom poses specific challenges, which often can hardly be addressed using typical acoustical or optical means. This significantly limits the possibilities of fish population monitoring and the use of fish detection for optimizing fishing techniques in such environments. Here, we investigate the potential of electrical impedance spectroscopy as a remote sensing technique for fish detection, to address this issue. The approach utilizes a set of electrodes to generate a low-intensity alternating electric current through water, and to measure the impedance. We conducted a number of experiments in which a fish was swimming in a glass tank. We measured changes in impedance at different frequencies, using different electrode arrangements, while simultaneously tracking the fish position with a pair of cameras. We also created numerical models of the experimental setup using the finite element method. The results of simulations were compared to the experimental data to test the accuracy of predictions and to determine if such a model could be a useful tool for designing detection setups for specific environmental conditions. We measured the robustness of the system to the presence air bubbles as a potential source of disturbances. Our results show a clear correlation between the observed drops in both real and imaginary parts of the measured impedance and the position of the fish. Model simulations showed qualitatively and quantitively similar results, indicating that such models could be suitable for practical applications.