The journey to acoustically tag endangered and critically endangered hammerheads

7th March 2023

Maria wants to help identify good areas to establish no-take zones for marine protected areas (MPAs) to protect hammerhead species. Her project focuses on scoophead and scalloped bonnethead sharks, and scalloped hammerhead sharks, which co-occur on Colombia’s Pacific coast. By looking at the variability in the type of habitats that these sharks are selecting, Maria hopes to be able to identify the best places to locate effective no-take (no fishing) zones. Her project is working towards this goal together with local fishers and communities, to reduce bycatch of these sharks in artisanal fisheries.
Read more about Maria’s project here.


Our journey started in Cali, Colombia, the third largest Colombian city which lies only 3 hours by car from the largest port on the Colombia pacific coast, Buenaventura. The one-way road goes through a large mountain chain where we crossed many different ecosystems until reaching the tropical rain forests of the biogeographic Chocó, an area of around 75,000 square kilometers on the Pacific Coast, spreading from Panamá to Ecuador. Due to a combination of evolutionary, ecological, climatic, and geologic factors, this region presents the highest biodiversity concentration per area in the world. After spending the night in Buenaventura, we took the earliest boat to Uramba Bahía Málaga, a Colombian National Natural Park established in 2010. The boat ride only took us 45 minutes, and we were welcomed by familiar faces from previous expeditions to this site. However, it took us almost two hours to offload all the heavy anchors, bricks, sacks of cement, acoustic receivers, tagging gear, and supplies. This part of Colombia is very remote, and you must bring everything you need to conduct your research from inland.

The first days were spent preparing the mooring for our acoustic receivers and meeting with the communities’ leaders to explain the project to them in more detail to keep strengthening our relationship with them and confirm their support, a critical step for every successful project in this region.

Fisher in the remote National Natural Park Uramba Bahía Málaga, Colombia. Photo by Maria Alejandra Herrera

Once we had everything in place, we were ready to start our research and meet the sharks that we so urgently need to protect. For now, our main study site covers an area of around 10 km from tip to tip. Here, four species of hammerhead sharks are found in good numbers. This is not a minor detail, given that some of these species disappeared from most places throughout their distribution range decades ago. In this area, we have found the Critically Endangered scalloped bonnethead (Sphyrna corona), scoophead (S. media), juvenile scalloped hammerhead sharks (S. lewini), and the Endangered bonnethead shark (S. tiburo). Three of these species are what you can call dwarf hammerheads, with one species maturing at around 50 cm in total length!

Adult male scalloped bonnethead captured, tagged, measured and released. It hasn't been easy to find males and this was the only one we caught during the whole expedition! Photo Emilio Posada

Once our moorings were in the water and our acoustic receivers were ready to start detecting tagged sharks in the murky waters of the Colombian Pacific, we started our tagging activities. The first caught shark was a scalloped bonnethead measuring 97 cm in total length, a whopping size for this species that was previously reported at 92 cm. We are very proud of holding this world record! After five days of fishing, we caught, measured, sampled, tagged, and released a total of 15 small hammerhead sharks, only missing the scoophead shark.

Our tagging efforts and the deployed acoustic array will allow us to study these four co-occurring hammerhead species’ temporal movement and occurrence patterns to identify priority areas where local no-take zones can be established. We have a lot of work ahead of us but we are excited to collect these data and work towards the conservation of some of the most threatened, understudied, and charismatic shark species in the world. We will return to this slice of paradise soon to download the first data and keep tagging more sharks.