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Endangered sharks: Study reveals hidden crisis of overfishing

A recent study has revealed that tens of thousands of endangered sharks and rays are caught annually by small-scale fisheries off the Republic of the Congo. 

Scientists conducting surveys at Songolo, home to over 60% of the country’s “artisanal” fishers, documented this alarming rate of catch over three years. This category of fishers operate small boats, equipped with small engines, and use hand-hauled lines and nets for their fishing activities.

Focus of the study

This extensive study, led by the University of Exeter in collaboration with the Wildlife Conservation Society (WCS) Congo Program and the Republic of the Congo’s fisheries department, recorded a total of more than 73,000 sharks and rays landed during the research period. 

Shocking discovery 

A significant finding of this study was that most of these caught aquatic creatures were juveniles, with a staggering 98% of the individuals belonging to species that are listed as vulnerable, endangered, or critically endangered on the IUCN Red List.

Encouraging findings

However, the researchers also have some encouraging news to report. The area in and around Songolo is abundant with sharks and rays, including the African wedgefish and the smoothback angelshark, two species previously believed to be locally extinct. 

This knowledge offers an opportunity for implementing measures that can protect these marine species while simultaneously supporting the livelihoods of the local fishers.

Central focus of the study 

Dr. Phil Doherty, the lead author of the study, emphasized that the goal isn’t to stop the artisanal fishers from fishing, as they rely on their catch for both food and income. 

“The devastating impact of industrial fishing fleets is well documented, but much less is known about the importance of small-scale fisheries,” said Dr. Doherty. “These fishers depend on their catch for food and income, so we’re not here to tell them to stop fishing.”

“Instead, by researching what they catch – including where and when – we can help to design measures that preserve shark and ray populations and ensure fishers’ livelihoods are sustainable.”

Triple threat

A concerning aspect noted by Dr. Doherty was the high proportion of juvenile sharks and rays in the catch, representing a “triple threat” to both fishers and biodiversity. 

“It’s bad for fishers because these smaller animals have less meat, and smaller fins for the valuable fin market,” he said. “Catching juveniles is also bad for the population, as these sharks would be the future breeding adults.”

“Thirdly, the high number of juveniles suggests this area may be a nursery ground for some species – and fishing in such an area could be disastrous for them.”

“Prolonged fishing by industrial fleets may have taken many of the larger individuals, meaning artisanal fishers have to settle for smaller ones. With many pressures faced by sharks and rays at different life stages, rapid population decline is highly likely.”

Effective management strategies 

The study played a supportive role in the establishment of the Republic of the Congo’s first marine protected areas last year. 

“Buy-in, trust, cooperation and inclusion of the fishers and in-country researchers is the only way these projects can succeed, and the only way to generate important data – which is necessary to create effective management strategies,” said Dr. Kristian Metcalfe, who has extensive experience working in the Republic of the Congo.

“For example, we found many juvenile scalloped hammerhead and blacktip sharks are caught at a certain time each year, so limiting fishing for these species at that time could allow populations to begin to recover.

“Changing equipment, such as adjusting the mesh size of gillnets to allow non-target species to escape, may be effective – as well as proposing the release of easily identifiable species such as the endangered African wedgefish.”

Study implications 

The researchers observed that the scalloped hammerhead and blacktip shark, listed as critically endangered and vulnerable respectively, were the most caught species, with over 50,000 individuals recorded. 

Given that surveys were conducted only 14 days per month on average and that more than 30% of artisanal fishers operate from locations other than Songolo, the actual numbers of sharks and rays caught are likely significantly higher than the 73,268 individuals recorded.

The study was funded by the Darwin Initiative, the Waterloo Foundation, the Waitt Foundation and the Save Our Seas Foundation.

The research is published in the journal Conservation Science and Practice.

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