Chinese firm develops robot to clean seaweed, mussel-covered ocean farm nets

With the deep-sea aquaculture in full swing, a large number of producers of marine engineering equipment have also grown exponentially.

Cleaning underwater cages covered with shellfish and seaweed at a depth of several tens of meters below sea level is a challenging task for deep-sea aquaculture practitioners.

If not cleaned regularly, the net cage may become too heavy and risk damage.

After nearly a year of research and development, Qingdao Sencott Intelligent Instrument, a maritime and aquaculture equipment maker in northern China’s Qingdao, came up with an underwater robot that can clean the cages without damaging the net.

In addition, it can thoroughly remove mussels and seaweed using precise algorithms, Chinese media reported.

Traditionally, due to the high cost of manual cleaning, fishermen in nearshore aquaculture would replace the nets every year. However, for deep-sea fish farming cages, the cost is much higher.

Generally, fishermen would hire divers to manually clean the cages or import underwater robots from abroad to do the job.

But they cost three to four million yuan each, and that’s not even including the after-sale maintenance costs.

“The most challenging part is not the technology, but the fact that such equipment has low usage, but requires high upfront investment,” said Zhou Kuizhao, a manager at Sencott.

He added that countries with more mature deep-sea aquaculture technology, such as Finland, were way ahead of China in the development of cleaning equipment.

To build its own variant, Sencott set up a team of more than 20 people to collaborate with the Ocean University of China.

After repeated experiments over nearly a year, they rolled out a high-performance underwater robot last year, breaking the technological monopoly of foreign countries.

“The core of the technology lies in the cleaning technique and algorithm,” Zhou explained. Working in the deep sea not only requires reliability but also the consideration that the cleaning process must not damage the cage.

During the cleaning process, the robot would spray jets of water from near its roller brush while producing a large number of bubbles.

When these bubbles burst, they shake off the shellfish attached to the cage and wash them away. Using bubbles instead of high-pressure water can protect the net cage, Zhou added.

It is reported that the team under his tutelage developed various types of underwater robots. For example, a small one can clean 1,000 cubic meters in an hour.

Currently, the size of a net cage in ocean farms is normally 60,000 cubic meters.

Under a manual cleaning mode, it will take at least four to five days to remove the sea life clinging to the cage. Weather conditions could also hamper the operation.

If a robot is brought in to help, it can complete the job in the space of one day — and cost less than half of manual cleaning.

In 2023, Qingdao, a city known for its fishing industry, has targeted 90 key marine projects, as part of the city’s efforts to shore up its maritime manufacturing industry.

With the deep-sea aquaculture in full swing, a large number of producers of marine engineering equipment have also grown exponentially.

The article was rewritten based on a draft copy by ChatGPT.

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Ni Tao

Ni Tao is the founder and editor-in-chief of cnrobopedia. Prior to cnrobopedia, he had a full decade of experience with a major state-run English-language newspaper as a tech reporter and opinion writer. He is also a communications specialist, having provided consultancy services to established firms like Siemens, Philips, ABinBev, Diageo, Group (Nasdaq: TCOM, HK: 9961), Jianpu Technology (NYSE: JT) and a handful of domestic startups. A graduate of Fudan University, he writes widely about China's business and tech scenes and other topics for global publications including South China Morning Post, SupChina, The Diplomat, CGTN, Banking Technology, among others, and tries to impart his experience to students at Fudan University Journalism School, where he is a part-time lecturer. When he's not writing about robotics, you can expect him to be on his beloved Yanagisawa saxophones, trying to play some jazz riffs, often in vain and occasionally against the protests of an angry neighbor. Get in touch with him by dropping a line at

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