Manuel Dureuil has been tagging and tracking the movements of elasmobranch (sharks, skates, and rays) in the waters of Cabo Verde off the coast of West Africa since 2015. The OTN researcher and Dalhousie PhD student works in a truly unique ecosystem – potentially one of the last remaining hotspots for sharks in the entire North Atlantic Ocean. The island nation of Cabo Verde contains more than 60 elasmobranch species, yet is also one of the least researched sites. Manuel hopes his work can change this.
Manuel is the president of Sharks of the Atlantic Research and Conservation Centre (ShARCC), a non-governmental organization that works to recover and maintain healthy populations of Atlantic elasmobranch species through research, education, and conservation projects. In December 2016, Manuel’s team tagged 14 Atlantic weasel sharks and nine nurse sharks with electronic tracking tags (full story here). Researchers hope this work will raise awareness for sharks in the West African region where detailed scientific information is scarce, preventing science-based management efforts. Recently, OTN spoke with Manuel to gather updates about his work in the Cabo Verdean islands of São Vicente and Maio.
São Vicente
Manuel’s team arrived in São Vicente on May 26, 2017. They outfitted three large weasel sharks with pop-up satellite archival tags. These tags use the Argos satellite system to track the movements of marine species, broadcasting location data and other monitoring information when the tag releases at a preprogrammed date. Tags were provided by the Thuenen-Institut of Sea Fisheries (Hamburg, Germany).
Manuel’s team also tagged six weasel sharks with Vemco V13 acoustic tags, bringing the total number of V13 tagged animals for this project to 20. OTN deploys and maintains the network of receivers that will track these acoustically tagged sharks in addition to providing personnel and ship time for this research.
Additionally, OTN field personnel successfully fitted several specimens with T-bar tags—small ID tags (like a driver’s license master number), which are used for mark recapture data, a method commonly used in ecology to estimate a species’ population size. T-bar tags also allow scientists to determine the mortality and growth of weasel sharks in this region. This happens when fishers capture a tagged shark taking body length and other measurements before releasing the animal and submitting the data to authorities.
A tagged Atlantic weasel shark is released in São Vicente.
An exciting development in the project was the first scientific documentation of blackchin guitarfish in the Cabo Verde region. Having gone locally extinct in some of its known geographical regions, the blackchin guitarfish is now listed as an endangered species under the IUCN Red List.
Manuel’s team was able to attach T-bar tags to three blackchin guitarfish during their time in São Vicente. All three animals were mature females, the largest of which measured 149 centimeters (over 6ft).
Education and outreach
A focus for the ShARCC team in Cabo Verde is getting local students and fishers involved in the work. Manuel spent time with Bachelor of Science students from the University of Cabo Verde, providing an informative presentation on conservation ecology of North Atlantic shark populations.
Local fishers became part of the research team helping locate, catch and release sharks and guitarfish while providing valuable local and historical knowledge.
Maio
After completing their work in São Vicente in early June, the team traveled to the island of Maio. The focus of this expedition was to teach locals and NGO researchers tagging and handling techniques. Manuel hopes that these collaborative efforts will help introduce a research project in Maio’s fishing communities.
The team established Maio’s first mark-recapture study by tagging an Atlantic weasel shark with a T-bar tag. The team also took biological samples from milk sharks found at several beaches. Researchers also caught a newborn female scalloped hammerhead shark at a multi-hammerhead species nursery. Previously, smooth hammerheads were the main species reported on this site. Measurements were taken on the neonatal hammerhead, but she was not tagged.
“The juvenile shark was really powerful when swimming away,” Manuel explained.
“Scalloped hammerheads are a highly threatened species, and deserve our attention and protection, especially in areas like Maio where we’ve seen illegal net-fishing occurring first-hand in areas where we know hammerhead nurseries are located. These illegal net-fishing practices indiscriminately kill any fish that swims into it, including these threatened animals.”
Manuel’s team was also shown a dead shark collected from NGO partners at a beach. Researchers believe the shark was a whitefin hammerhead, which could potentially be the second new species discovered during the trip along with the guitarfish found in São Vicente.
Throughout the trip, Manuel’s team spent time with representatives from the Maio Biodiversity Foundation to teach external passive tagging methods. Moving forward, these researchers will have the skills needed to continue tagging operations.
OTN researcher/Dalhousie PhD student, Manuel Dureuil, teaches an employee from Maio Biodiversity Foundation how to properly insert passive t-bar tags into a small milk shark carcass found by the team.
For more information including project stories, highlights, and photographs visit ShARCC’s Facebook page.