Hangzhou deploys biomimetic robotic fish for West Lake patrols

A biomimetic robotic fish patrols West Lake in Hangzhou, east China's Zhejiang province. (Photo courtesy of the Information Office of the Hangzhou Municipal People's Government)

"Look, there's a shark in the lake!" On weekends, visitors boating on Hangzhou's iconic West Lake often exclaim in surprise. Upon closer inspection, the dark, shark-like creature measures about 60 to 70 centimeters in length and features remarkably lifelike eyes, a mouth, fins, and a tail.

But it is not a shark at all. It is a custom-designed biomimetic robotic fish, developed specifically for West Lake's unique environment, according to Liu Yuping, chief of the ecological police division of the West Lake Branch of the Hangzhou Public Security Bureau.

"Modeled after a lemon shark, the robotic fish weighs about 4 to 5 kilograms and can easily be lifted with one hand," said Liu.

Its gray outer shell is made of a specialized material that closely mimics the texture of real fish skin. Inside the sealed body are the battery and control system, while two high-definition underwater cameras are embedded in its head.

"The robotic fish was jointly developed by our team and the Institute of Automation under the Chinese Academy of Sciences," said Gong Yingqiang, head of the Environmental Resources, Food and Drug Crime Investigation Division of the same bureau.

After nearly a year of development, the team overcame several technical challenges, including flexible tail-fin propulsion, underwater obstacle avoidance, and ultra-low-noise operation. The final version of the robotic fish is capable of round-the-clock submerged patrols. It also works in coordination with unmanned vehicles, robotic dogs, drones, and smart roadside devices to form an integrated security network.

Propulsion is what enables the biomimetic fish to move efficiently underwater. According to Liu, its tail, made of a flexible material, moves like that of a real fish, providing the thrust needed for agile turns. Two side fins help it stay submerged and allow it to dive to depths of over 10 meters.

Under remote control, the robotic fish can swim forward, turn, dive, and accelerate. "Its propulsion system gives it full 360-degree maneuverability and up to four hours of battery life," Liu said. With a tail-beat frequency of 1 to 5 hertz and a speed of 0.3 meters per second, it creates almost no noticeable water disturbance when operating in shallow water.

Biomimetic robotic fish patrol West Lake in Hangzhou, east China's Zhejiang province. (Photo courtesy of the Information Office of the Hangzhou Municipal People's Government)

As it approached a waterbird during testing, the robotic fish automatically slowed down, leaving the bird undisturbed. "It not only avoids disturbing aquatic wildlife but can also autonomously steer clear of rocks, aquatic plants, and other underwater obstacles, minimizing its impact on the lake ecosystem," Liu added.

"The robotic fish is designed primarily for ecological protection and public safety," Gong said. "In the past, patrols, inspections, and retrieval operations on West Lake relied largely on manual labor, making them less efficient and more disruptive to the aquatic ecosystem," he said, adding that the robotic fish was developed to address these challenges.

Equipped with two high-definition underwater cameras and other sensors, the robotic fish transmits real-time underwater footage to the command center as it patrols. "It can monitor water temperature and pH levels, identify invasive species, and support ecological monitoring and biodiversity surveys," Liu said.

The robotic fish can also help recover mobile phones and other electronic devices accidentally dropped into the lake by visitors, a task previously carried out using retrieval poles.

Staff members release biomimetic robotic fish into West Lake in Hangzhou, east China's Zhejiang province. (Photo courtesy of the Information Office of the Hangzhou Municipal People's Government)

According to Gong, the robotic fish has introduced a new model for patrol and public safety operations on West Lake, enabling unobtrusive patrols, silent protection, and precision surveillance, putting technological innovation to work in frontline public safety.