MarAlliance has conducted a pioneering study to explore the relative diversity and abundance of shark species within the Cabo Verde archipelago. Our latest publication stands as the first baseline study of shark populations in Cabo Verde’s waters, providing critical insights into the biodiversity and ecological significance of these marine predators.

The Cabo Verde archipelago, consisting of ten islands of volcanic origin, is situated 500 kilometers west of the Senegalese coast and is recognized as a critical marine biodiversity hotspot, where each island contributes uniquely to the region’s ecological wealth. The western islands of Cabo Verde, characterized by rugged terrain and lush vegetation, contrast with the more arid eastern islands, which are dominated by sand dunes and eroded landscapes. Despite these differences, all islands share a common trait: they harbor an incredibly diverse marine ecosystem. The easternmost islands—Maio, Boavista, and Sal—are particularly notable for their abundant marine life. This region hosts a variety of species, from loggerheads and green turtles to humpback whales, numerous species of dolphins, and, of course, sharks and rays.

It is estimated that Cabo Verde’s waters are home to at least 50 different species of sharks and rays, collectively known as elasmobranchs. These include the iconic tiger shark, whale shark, oceanic manta ray, the critically endangered scalloped hammerhead, and endemic species found only in this region, such as the Atlantic weasel shark. While there are many accounts of shark encounters in Cabo Verde, comprehensive and official data on their distribution and population status has been sparse.

Research Methodology: Deploying BRUVS

Between 2015 and 2017, MarAlliance conducted extensive surveys to address the knowledge gap on shark and ray species in Cabo Verde. The goal was to establish a baseline of their diversity and abundance, which could be used to assess the present conservation status of elasmobranchs and to detect future changes in their populations and distribution in relation to environmental changes, fishing, and conservation measures.

Led by the late national coordinator Zeddy Seymour and supported by a trio of artisanal fishermen brothers the late Ze Luis Monteiro, and Angelito, and Carlos Monteiro, the team deployed Baited Remote Underwater Video Systems (BRUVS) guided by a strategic design formulated by Dr. Rachel Graham, MarAlliance’s founder. These devices, consisting of metal frames with underwater cameras and baited cages to attract fish and sharks, were deployed in a spoke-and-wheel pattern surrounding the islands of Sal, Boavista, and Maio to detect and count shark and ray species.

This methodology ensured comprehensive coverage of nearshore waters, resulting in the deployment of 204 BRUVs and the collection of over 200 hours of footage.  The footage included 215 sightings of sharks and rays from 14 different species, highlighting a diversity of elasmobranchs that left our team pleasantly surprised. The data also indicated significant variation in species abundance and distribution across the islands.

• Sal: The east coast is home to a high number of tiger sharks and stingrays.
• Boavista: A mix of top and meso-predatory sharks, particularly near Sal Rei.
• Maio: Dominated by non-carcharhinid species like smoothhounds and nurse sharks, with fewer top predators.

Mapping the sightings allowed our team to identify critical areas for conservation. For instance, the east coast of Sal, the northwest of Boavista, and the eastern coast of Maio were found to have high concentrations of sharks and rays.

Results and Future Directions

One of the key results identified was the low presence of large bodied sharks in Maio compared to Boavista and Sal. The proximity of Maio to Santiago, Cabo Verde’s most populated island, suggests that overfishing may have significantly impacted larger shark species. Now that fish stocks in Maio are anecdotally becoming scarce, local fishermen have started moving north to Boavista and Sal in search of more abundant fishing grounds. Simultaneously, the booming tourism industry is attracting more people to Sal and Boavista, driving a rising demand for locally sourced seafood.

As fishing pressure increases, the future of Cabo Verde’s shark populations remains uncertain. Our findings underscore the urgent need for targeted conservation efforts to protect these late maturing and long-lived species and ensure ecosystem functioning, greater sustainability of local fisheries, and improved effectiveness of protected areas in the country to protect elasmobranchs during part or most of their life-cycle. Although Cabo Verde consists of a small group of islands, its importance to the eastern tropical Atlantic Ocean is emphasized by the remarkable biodiversity hosted within its waters. Working with local communities who highly depend on the continued health of the surrounding waters, our collaborative research in this understudied region showcases that overfishing of coastal resources remains a common problem worldwide and, once again, shows the importance of collecting baseline information from which to measure changes in abundance, distribution and diversity of species. Our work in Cabo Verde from 2015 onwards has identified and filled in several crucial knowledge gaps that have shifted attitudes towards sharks, shaped conservation action and policy-making, as we identified critical habitats and revealed the spatial ecology of several species of sharks, rays, and even turtles that inhabit these waters while characterizing threats to their persistence.