Prototype of a robotic fish

Autonomous robotic fish designed to monitor water quality

Image credit: Claudio Rossi/UPM

Researchers have developed a biomimetic robotic equipped with chemical sensors to detect and respond to the pH of water. They hope that the invention will help maintain good health in fish farms.

Overfishing in the wild and a global increase in demand for fish has encouraged the growth of aquaculture: the farming of fish and other aquatic organisms.

Aquaculture is now the fastest growing animal food sector in the world; farmed fish and other seafood make up about half of all fish consumed globally. In order to keep aquaculture systems healthy and avoid disease in the tightly-packed fish populations, it is important to monitor and control water quality and nutrition.

Aiming to help keep farmed fish healthy, researchers from the Universidad Politécnica de Madrid (UPM) and the University of Florence collaborated to develop a bioinspired robot with chemical sensors to track the quality of water.

In aquaculture, fish live in greater densities than wild fish, causing natural processes to accelerate. As fish and bacteria breathe, carbon dioxide is released into the water, forming carbonic acid and lowering the pH of the water. Meanwhile, as biological waste breaks down, hydrogen ions are released, also increasing the acidity of the water. Water acidity directly affects water quality and fish health.

The prototype fish can measure the pH of water with chemical sensors, and detect in situ real-time anomalies.

Its specially designed electrochemical PH sensor is based on a polyaniline film, deposited on a graphite electrode surface. This sensor collects data to inform the fish’s swimming patterns and directions, helping it identify areas of concentration.

The robotic fish is designed to mimic a fish in order to minimise disruption and stress to fish populations. It is biomimetic; it mimics both the appearance and function of a fish.

The prototype is 30cm long not including its tail, and built from shape memory components which induce a slim, flexible ‘backbone’ (made of polycarbonate) to bend. Latex skin covers a structure of ribs.

“Thanks to this system that provides early information on environmental change, we can control the parameters of water quality and improve management decisions of fish farms, and consequently, the wellness of these animals,” said Professor Claudio Rossi of the centre for automation and robotics at UPM, and developer of the robotic fish.

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