Tanzania · Since 2024
Tanzania Blacktip Reef Shark Project
Testing whether a no-take reserve off Mafia Island, Tanzania, is a nursery for young blacktip reef sharks.
Blacktip reef sharks are seen regularly in the shallows around Thanda Island, inside a no-take marine reserve off Mafia Island. We are testing whether the reserve is a nursery for the species, and how many young sharks use it.
Blacktip reef sharks (Carcharhinus melanopterus) are listed as Vulnerable on the IUCN Red List, and their global population is decreasing. In December 2024, MMF and Thanda Island began monitoring the young sharks that use the Shungimbili Island Marine Reserve, off the northwest coast of Mafia Island in Tanzania. MMF Principal Scientist Dr. Chris Rohner leads the project, as he does our long-running Mafia Island whale shark research, which began in 2012; the two projects share a field team and logistics. Thanda Island is a scientific collaborator and a funder, and the Tanzania Fisheries Research Institute (TAFIRI) supports the work. The Sharkbook.ai team is helping develop automated identification of individual sharks.
Objectives
- Determine whether the Shungimbili Island Marine Reserve functions as a nursery area for blacktip reef sharks.
- Build a photo-identification catalog and monitor the population over time through Sharkbook.ai.
- Assess the population’s size, structure, site fidelity, and habitat use.
- Develop a camera-based monitoring method that other blacktip reef shark projects can use.
- Investigate what drives the sharks’ abundance, including tides and seasons, and the potential threats they face.
What's next
- Match fin images from every survey trip to build the identification catalog.
- Train an automated identification tool for blacktip reef sharks on Sharkbook.ai.
- Add stereo cameras for more precise size measurements, and test deployments at night.
- Use genetics and acoustic tracking to learn whether the same females return to give birth, and how the sharks move and use their habitat as they grow.
- Talk with local fishers to understand the risks the sharks face outside the reserve.
The stereo cameras, acoustic tracking, and genetic work will each need dedicated funding.
Support our shark research at Mafia Island
This project shares its field team and logistics with our Mafia Island whale shark research. Your gift supports the camera surveys and the photo-identification work behind them.
Our work on blacktip reef sharks in Tanzania
Counting sharks on camera
We use baited remote underwater video systems (BRUVs): a camera pointed at a bait box, left on the seabed for about 30 minutes. From the footage, the team counts the most sharks visible in a single frame, estimates each shark’s fork length (from the snout to the fork of the tail) against a measuring stick attached to the frame, and extracts still images of its left dorsal fin.
Telling individual sharks apart
Each shark’s fin carries a unique pigment pattern, so the images let us recognize individuals; they are matched on Sharkbook.ai, the same platform that holds our Mafia Island whale shark identifications.
A nursery in a protected area?
An area counts as a shark nursery when young sharks are more common there than elsewhere, stay there for long periods, and use it year after year. The study is designed to test all three, and the last needs several years of monitoring. We will share the results once they are published.
MMF Project Team
Dr. Chris Rohner
Jens Paulsen
Dr. Clare Prebble
Dr. Simon PierceCollaborators and Partners
Tanzania Whale Shark Project