Projects in Tanzania

Tanzania Blacktip Reef Shark Project

What’s this project about?

Blacktip reef sharks are seen regularly in the shallows around Thanda Island, inside a no-take marine reserve off Mafia Island. We are finding out whether the reserve is a nursery for the species, and how many young sharks depend on 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.

Project Overview.

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, measures each shark against a scale bar, and captures images of its dorsal fin. Each shark’s fin is different, so the images let us recognize individuals, and they are matched on Sharkbook.ai.

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.

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 where the sharks go as they grow.
  • Talk with local fishers to understand the risks the sharks face outside the reserve.

Project leader

Dr. Chris Rohner

Principal Scientist

Chris leads MMF’s research at Mafia Island, where he has studied whale sharks since 2012.

Collaborators

The project is a partnership with Thanda Island, with support from the Tanzania Fisheries Research Institute (TAFIRI) and WWF Tanzania. The Sharkbook.ai team is helping develop automated identification. Thanda Island supports the project and hosts the team.

The project shares its field team and logistics with our long-running Mafia Island whale shark research.