Underwater Fish Monitoring Through Vortex-Induced Vibration Sensing

Underwater fish and marine animal monitoring is important in assessing biodiversity and the health of aquatic ecosystems as well as for understanding the impacts of offshore structures on those animals. Existing methods, such as acoustic sensing, tagging, flow field sensing, and optical imaging, are often energy-intensive, invasive, fragile, or dependent on lighting conditions. Inspired by the sensory mechanism of seal whiskers, we introduce an energy-efficient, non-invasive marine animal monitoring method based on vortex-induced vibration (VIV) sensing. The main intuition of our method is that as marine animals swim, they generate characteristic vortex patterns and turbulence that propagate through water. By detecting these VIV signals, our system can identify the movement of these animals. A key challenge lies in capturing these low-amplitude, rapidly dissipating vortices. To address this, we design a flexible sensor mounting structure in which the sensor is suspended by a string from a fixed base, allowing adaptive movement in response to vortex-induced flow. We validate the system in a water tank using swimming fish toys and other objects to induce vortices, achieving a classification accuracy of 96.88%, demonstrating its effectiveness and potential for monitoring underwater fish and marine animals.