- Israeli scientists have developed a solar-powered underwater robot called SOUND that can roam autonomously for five days at a stretch, counting fish and communicating its findings back to observers onshore.
- The goal is to help local fishers in developing countries understand their fish populations so they can avoid overfishing and the capture of unwanted species.
- They tested the system in Malawi, among other locations, where fishers are facing a myriad of problems related to uncontrolled fishing.
LAKE CHILWA, Malawi — When fishers on Lake Chilwa cast their nets, they don’t know whether there are fish below, or something else entirely.
“We don’t go out in the lake to check what we have where. We go to fish,” Anderson Thembwa, a fisher since 1994 and chair of the Lake Chilwa Fisheries Association, tells Mongabay. The cooperative of 36 committees comprising fishers and community leaders manages fishing on the lake, landlocked Malawi’s second-largest fishing ground. “You pull the net and you realize all you have down there are frogs, crabs, juvenile fish and debris,” Thembwa says.
A new system could help them check not only what kind of fish they have and where, but also how much. That way they can avoid the overfishing that’s threatening livelihoods on Lake Chilwa and elsewhere, as well as scooping up all those unwanted lake dwellers in their nets.
The system in question? It’s not a net, but a robot: A solar-powered, transparent cylinder a meter (3 feet) long that can roam the waters autonomously for five days at a stretch, counting fish.
“Our project, which we call SOUND, was aimed to solve these problems by in situ measuring number of fish, detecting schools of fish, estimating size of individual fish, thereby the biomass of the fish,” Roee Diamant, head of the Underwater Acoustics and Navigation Laboratory at the University of Haifa in Israel, tells Mongabay. He and his team developed the robot for use by regulatory authorities or fishers’ groups like Thembwa’s so they can draft rules to effectively manage fishing. The focus is developing countries, where fish stocks are increasingly under pressure as global demand for fish products rises.
In December 2024, Diamant’s team worked with scientists from Lilongwe University of Agriculture and Natural Resources in Malawi to test the SOUND system in Lake Malawi, the country’s biggest fishing ground. They also tested it in Israel and Croatia.
Down in the water, the robot maintains depth while scanning the area with active sonar and transmitting signals through satellite communication if it detects fish. Fishers or authorities can receive the data via SMS texts or email. It produces no noise to avoid scaring fish away, thus ensuring better fish detection. During trials it was able to detect individual fish as short as 6 centimeters (2.4 inches) within a 100-m (330-ft) radius, Diamant says.
Traditional fish monitoring methods based on manual sampling are, as a 2022 paper put it, “time-consuming, laborious and intrusive.” Hydroacoustic systems are among technologies that can monitor fish populations in their habitat unobtrusively and with greater precision. Detection systems similar to SOUND’s are in use on fishing vessels around the world. What makes SOUND innovative and efficient in monitoring fish populations is its ability to detect fish omnidirectionally, in a ball around itself, and its combination of energy efficiency, depth control, autonomy, and ability to communicate its findings, according to Diamant.
“Now making a robot that runs autonomously, not from a vessel but by itself, continuously and without deploying it from a boat or something like that makes our system unique,” Diamant says.
Overfishing and bycatch of unwanted species affect fisheries worldwide, he says, and instruments such as SOUND are aimed at improving control.
“What we need is to make fishing sustainable,” Diamant says. “By using these technological aids, that would help us find the fish. The result would be controlled fishing.”
According to Diamant, one of the SOUND robot’s biggest expected impacts is efficiency: Fishers could spend less time on the water as they would know where exactly to find fish instead of having to rely on trial and error like the Lake Chilwa fishers do. It would also mean less fuel consumed by boats searching for schools of fish, and less degradation of nets due to trawling where there are no fish.
Kassam Daud, a fish biotechnology and biodiversity conservation professor at Lilongwe University of Agriculture and Natural Resources, helped test the robot in Lake Malawi. He says bottom trawling, which many developing countries use to sample fish for monitoring, is environmentally destructive and takes fish out of the water.
Daud says the remotely operated underwater cameras that the Department of Fisheries in Malawi uses to assess fish diversity are limited in scope, as the equipment can’t go deeper than 60 m (200 ft).
“Therefore, SOUND floaters bring in a joint solution to the destructive fishing methods and depth restriction by the current methods,” Daud says.
However, adoption of the technology by commercial fishers will depend on affordability of purchase and operational costs, and whether it helps them catch more fish than they could without it, according to Daud.
Daniel Jamu, a local fisheries expert who led a USAID-funded project that designed and introduced a remotely operated underwater vehicle on Lake Malawi to monitor stocks, says that system was able to assess fish quantity and identify fish species groups.
“If the Israel method is successful in identifying and measuring fish sizes and quantity in its natural environment, it will indeed be a game changer,” says Jamu, who wasn’t involved in the SOUND project.
Back at Lake Chilwa, Thembwa says his cooperative welcomes any intervention that helps it avoid depletion of fish in the lake.
“We need such tools because right now, the situation is very bad here,” he says after being briefed about the SOUND technology.
Intensive farming in the lake’s catchment area, which is increasing siltation, and the growing regional population are exerting pressure on fish resources in the lake. Regulating fishing is becoming increasingly difficult, Thembwa says.
Seated on a bench inside a grass shelter on the beach in January, Thembwa casts his eyes across the water. “You see those?” he says, pointing at two objects at the far, misty end of the lake. “Those are fishing boats. We closed fishing officially on December 1, until March 30, for fish to breed. Yet there they are, fishing. Fishers are becoming hostile and that’s a nightmare for us,” he says.
The association is also finding it hard to eradicate indiscriminate fishing practices that threaten the sustainability of the lake’s fish stocks, such as the use of mosquito nets and other small-meshed nets that catch immature fish before they can breed.
The group doesn’t have boats for patrols, and it struggles to raise money to hire police to help enforce regulations. Association members work voluntarily, their only motivation being that the lake is the source of their livelihood.
“But we can only go so far. It’s tough and we need everything, including automation of fish monitoring and fishing regulation if that helps us to save the situation on the lake,” Thembwa says.
Diamant says his team will next provide SOUND robots to some fisheries research centers and regulatory authorities in Malawi and elsewhere to gather feedback so they can refine the system before distributing it for use.
“Our goal is really to make an impact. We want it to be very low cost so that it is affordable,” Diamant says.
Banner image: Artisans fix nets at Chikombe Beach on Lake Malawi, the largest fishing ground in Malawi. Image by Charles Mpaka for Mongabay.
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Citation:
Wei, Y., Duan, Y., & An, D. (2022). Monitoring fish using imaging sonar: Capacity, challenges and future perspective. Fish and Fisheries, 23(6), 1347-1370. doi:10.1111/faf.12693
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