- Between 2015 and 2023, researchers working with fishers recorded more than 7,000 sharks and rays caught at sea and landed along Cameroon’s coast.
- The recorded animals represent 45 species, of which 13 are critically endangered.
- Their research found that most sharks and rays landed in Cameroon’s fisheries are juveniles, raising serious concerns about population recovery.
- The data help scientists better understand species composition, catch trends and conservation priorities along Cameroon’s coast.
BUEA, Cameroon — To his fishing peers, Ojah Alfred, 45, is a fisher like they are. But to Cameroon’s scientific community, he is also a scientist — a citizen scientist.
For eight years, Alfred, alongside more than 80 other fishers across Cameroon’s three coastal regions, has been collecting data on marine species brought to landing sites and caught out at sea, using the Siren app, a citizen science platform.
“I never imagined that the pictures I take every day of fish with the Sirens app would lead to the publication of this ‘big book,’” Alfred told Mongabay, referring to a study published in December in the journal Environmental Biology of Fishes.
The “big book” is the first detailed snapshot of shark and ray diversity in the country, helping fill a major knowledge gap that has long hindered conservation and fisheries management.
Many of the species being caught in Cameroon’s fisheries are already at risk of extinction worldwide, and the country has no specific laws protecting sharks and rays, according to Ghofrane Labyedh, the study’s lead researcher.
The fishers’ data, along with fish market surveys, recorded 45 species of sharks and rays in Cameroon’s waters, of which 36 are considered threatened by the International Union for Conservation of Nature (IUCN), including 13 classified as critically endangered.
Alarmingly, most are caught before reaching maturity, raising serious concerns about the future of these populations.
“Almost 90% of the species are caught at the juvenile stage,” said Labyedh, who is also the regional vice chair (Africa) for the IUCN SSC Shark Specialist Group. Catching individuals before they can reproduce significantly reduces a population’s ability to recover and sustain itself over time, Labyedh said. If the trend continues, some species could disappear entirely, according to her.
The study’s data were collected between 2015 and 2023. During the study period, researchers recorded a total of 7,097 specimens: 5,353 rays and 1,744 sharks.
The study revealed that of the critically endangered shark and ray species recorded along Cameroon’s coast, the most frequently landed are the blackchin guitarfish (Glaucostegus cemiculus) and the scalloped hammerhead shark (Sphyrna lewini).
Alfred, who has been fishing for about 20 years, is familiar with the scalloped hammerhead shark, which he described as the largest shark species he has encountered while fishing. They swim in groups, he explained, adding that if one becomes entangled in a fishing net, the others often follow. “I do not go to sea to fish for sharks,” Alfred said, but “when fishing, sometimes they get entangled in the net.”
Globally, an estimated 50 million sharks are caught as bycatch each year, many of them caught by industrial tuna longlines and purse seiners.
While Alfred continues to encounter scalloped hammerhead sharks, he said blackchin guitarfish, once a common sight, are now rare.
Their dwindling numbers could have wider ecological consequences. Sharks and several species of rays are apex predators, meaning they help regulate fish populations and maintain the balance of marine ecosystems. Their disappearance could disrupt food webs and affect the health of coastal fisheries.
Tracking a decline in fisheries and capturing declining diversity is harder without a clear sense of what exists in the seas.
The idea for the research project was born more than six years ago. In 2019, Labyedh traveled from her native Tunisia to Cameroon for a two-month internship, during which time she intended to study whales. She spent several days at sea searching for whales but did not encounter a single one.
“But every day I went to the fish markets in Kribi [a port city], I was seeing different species of sharks and rays of all sizes,” she told Mongabay. “When I did my research, I didn’t find any articles or reports on sharks and rays in Cameroon.”
The Siren app was launched in 2015 by a Cameroonian marine biologist and conservationist, Aristide Takoukam Kamla, a co-author on the December study, to enable volunteers, particularly fishers, to document and share observations of marine wildlife using their mobile phones. The app allows users to record sightings offline. It automatically captures GPS coordinates and a timestamp. Once uploaded, the data are validated by scientists, who are part of the Siren team, and made public.
“We had to complement data from the Siren app with fish market surveys,” Labyedh said. These surveys, she explained, allowed researchers to collect additional scientific details, including the sex and maturity of specimens — information that fishers using the Siren app could not easily record.
For Cornelius John, a 31-year-old fisher from the coastal town of Kribi who also contributed to the study, rays are more common as bycatch than sharks. “Most of them are usually very young,” he said.
Juvenile fish are smaller in size than adults and fetch lower prices. The researchers contend that fishers can be persuaded to release the juveniles alive, since this would not make a significant dent in their incomes.
While it may be possible to persuade artisanal fishers to release sharks and rays caught unintentionally, Labyedh said industrial fishing vessels, many of which practice bottom trawling, pose an even greater threat.
A 2021 study warned that globally, overfishing poses the most significant risk to sharks and rays. Even if they are not targeted, increasing fishing pressure increases the threat to sharks and rays that are pulled in as bycatch.
Cameroon’s waters have long been vulnerable to illegal, unreported and unregulated fishing. Labyedh is advocating for limits on industrial fishing activities, improved management of existing marine protected areas, the designation of new protected zones and legal protection for critically endangered species such as the blackchin guitarfish and the scalloped hammerhead shark. Even within Cameroon, there is no specific law to protect sharks and rays, Labyedh said.
According to the Labyedh, the next phase of the work will involve acoustic monitoring, analysis of environmental DNA (eDNA, genetic material left by organisms in the environment) and the tagging of sharks and rays to determine whether hitherto unreported species are present, identify nursery grounds and track their movement patterns.
“Most, if not all, of these species are migratory and do not recognize national borders,” she said, adding that regional collaboration among countries is important to safeguard populations in these waters.
Effective conservation measures depend on reliable data, something Cameroon lacked, she said. “But with this study, it becomes easier to convince the government to legally protect them.”
Involving fishing communities in the research is also instilling a sense of confidence among participants. “I now believe that I am a scientist,” Alfred said, standing in Down Beach in Limbe, where fishers like him dock their fishing vessels. He reflected on the changes he has witnessed and said, “We used to stand here and watch dolphins playing some years back, but now they are nowhere to be found.”
“Where have they gone?” he asked. “I want the next generation to see dolphins and other marine species too, and I now believe that the work I am doing can help.”
Banner Image: Artisanal fishing vessels lined up at Down Beach, Limbe, Cameroon. Image by Shuimo Trust Dohyee for Mongabay.
Citations:
Labyedh, G., Laglbauer, B., Fogwan, C., Biankeu, C., Mengoue, G., Stevens, G. M., … Kamla, A. T. (2025). Shining a light on Cameroon’s elasmobranch fisheries: Insights from citizen science and market surveys highlight a conservation priority. Environmental Biology of Fishes, 109(1). doi:10.1007/s10641-025-01771-y
Dulvy, N. K., Pacoureau, N., Rigby, C. L., Pollom, R. A., Jabado, R. W., Ebert, D. A., … Simpfendorfer, C. A. (2021). Overfishing drives over one-third of all sharks and rays toward a global extinction crisis. Current Biology, 31(22), 5118-5119. doi:10.1016/j.cub.2021.11.008
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