Mozambique
Mozambique Bull Shark Research Project
Acoustic and satellite tracking show that Mozambique's bull sharks include year-round residents of the Bazaruto Archipelago and migrants that travel thousands of kilometers across national borders.
Bull sharks (Carcharhinus leucas) are among the top predators along the Mozambican coastline and play a vital role in marine ecosystems. However, fisheries assessments have revealed a drastic increase in shark catches in recent years, indicating the need for swift and effective management action.
This project combines several techniques to investigate the fine- and broad-scale movements and connectivity of bull sharks (also known as Zambezi sharks), addressing key knowledge gaps for this important coastal predator in southern Africa. Our researchers and collaborating partners coordinate research at several locations in Mozambique, using a range of methods to investigate the species’ movement ecology, habitat use, genetic connectivity (the extent to which separate groups interbreed), and trophic position (its level in the food web). Lukas Müller set up and led this project for MMF, carrying out much of its tracking work in the Bazaruto Seascape.
Objectives
- Investigate the regional and transboundary movements of bull sharks.
- Understand their fine-scale movement patterns and habitat use.
- Determine the connectivity of bull shark population(s) in southern Africa.
- Characterize, and help resolve, the conservation conflict between local communities and these predators.
What we've done
- Identified numerous aggregation sites for bull sharks throughout southern Mozambique, positioning our team to conduct focused research on the species.
- Collected observational sightings data from some of these sites for almost a decade before we began more formal work on the species in the province.
- Tracked 38 bull sharks through the Bazaruto Seascape on a passive acoustic array (a network of underwater receivers), with detection records from 2012 to 2024. Some were tagged at Bazaruto and others farther south in Mozambique and South Africa; individual sharks were also fitted with satellite tags.
- Joined a regional network: our receivers now form part of a network spanning roughly 400 kilometers (250 miles) of the Mozambican coast, shared with collaborators in South Africa and across the western Indian Ocean. A 2023 study using a wider network of 350 receivers between South Africa and Mozambique, co-authored by MMF’s Dr. Stephanie Venables, found that 63% of the tagged bull sharks crossed the border between the two countries.
- Documented year-round residency by individual bull sharks in the Bazaruto Seascape, alongside visiting sharks from farther south, including two males from South Africa’s Breede River that returned every year after they were tagged.
- Collected fin clips and muscle tissue samples from tagged sharks for genetic and stable isotope analyses (chemical markers in tissue that reveal diet and position in the food web).
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Our work on bull sharks in Mozambique
From rivers to reefs
Bull sharks can live in marine, brackish, and freshwater environments. As large-bodied, mobile predators, they likely play a vital role in the functioning of the different aquatic ecosystems they move through along the eastern African coastline.
Estuaries, mangroves, and rivers are critical nursery habitats for bull sharks, and females have shown strong philopatry, returning to the areas where they were born to give birth. Recent studies in southern Mozambique have shown that bull sharks remain resident in marine reef systems, yet are also capable of long-distance return migrations of hundreds of kilometers. One acoustically tagged individual traveled more than 2,200 kilometers (1,370 miles) between the Breede River in South Africa and the Bazaruto Archipelago in Mozambique in 119 days, the longest coastal migration recorded in the 2023 transboundary study.
Our collaborative tracking work went further still. A female bull shark moved from Mozambique around the southern tip of South Africa to the Nigerian coast, a journey of more than 7,000 kilometers (4,350 miles) and the first documented movement of the species between ocean basins. The journey was published in the journal Ecology in 2025 by a team led by Dr. Ryan Daly of the Oceanographic Research Institute, with MMF’s Dr. Stephanie Venables as a co-author.
Fishing pressure
Fisheries assessments have revealed that shark catches in Mozambique have increased by up to 220% in recent years. Bull sharks are listed as Vulnerable on the IUCN Red List, and they are among the most commonly landed species in some areas of Mozambique, making up as much as 17.3% of total shark catches. Their long-distance migrations and movements between marine and freshwater environments make them especially vulnerable to capture in seine net and gillnet fisheries.
Bull sharks are also particularly susceptible to habitat degradation and pollution, because they rely on sensitive habitats such as estuaries, mangroves, and shallow bays. Declining catches, such as those recorded in shark nets in South Africa, suggest localized depletions of bull shark populations in some areas and highlight the species’ vulnerability to exploitation.
Bull sharks and people
Frequent interactions between people and bull sharks in coastal habitats have resulted in numerous fatalities in Mozambique. Resentment toward the species, and active persecution in some communities, pose an additional challenge for the conservation and management of bull sharks.
Until recently, a lack of data on the species’ distribution, habitat use, and population structure made it difficult for scientists and managers to adequately assess and address other potential threats to bull sharks in the country. Filling those gaps is the purpose of this project.
Residency and seasonal migration
More than a decade of acoustic tracking has revealed two contrasting patterns of habitat use. Some bull sharks, mostly mature females, are residents of the Bazaruto Seascape, detected on almost half of all monitored days and punctuating that residency with brief excursions; one female, for instance, was detected on just three receivers across more than five years of tracking. Others are visitors tagged farther south, in southern Mozambique and South Africa, that pass through the seascape on short stopovers during coastal migrations, most lasting less than five days.
The team fits sharks with acoustic tags, and some with satellite tags, and samples their tissue for genetic and stable isotope analyses. (Photo: Uli Kunz.)
A network of habitats
The sharks also use the seascape’s reefs in complementary ways. At a rocky ridge 40–45 meters (130–150 feet) deep off northern Bazaruto Island, about 72% of detections occurred during the day, whereas the neighboring reef about 3 kilometers (2 miles) away recorded more detections at night, largely from one highly resident female. Inshore sites off the San Sebastian Peninsula recorded the most activity before dawn. Taken together with the long-distance movements now documented between Mozambique, South Africa, and beyond, these patterns indicate that protecting bull sharks means protecting a network of habitats across national borders, not a single site.
The full analysis of bull shark habitat use across the Bazaruto Seascape, led by MMF’s Dr. Stephanie Venables with colleagues Dr. Chris Rohner and Nilza de Catarina, was published in 2026. It found that adult bull sharks are present year-round, with core habitat concentrated on the seaward reefs and inshore off the San Sebastian Peninsula. Existing marine protected areas cover 82% of that core habitat, although important habitat extends beyond their boundaries, and transient sharks use the seascape as a seasonal waypoint on a regional movement corridor, mainly between May and November. (Photo: Uli Kunz.)
MMF Project Team
Dr. Stephanie Venables
Dr. Chris RohnerRecent research
- 2026Habitat use, residency, and connectivity of bull sharks (Carcharhinus leucas) in the Bazaruto Seascape, Mozambique
- 2025Breaking barriers: Transoceanic movement by a bull shark
- 2023Persistent transboundary movements of threatened sharks highlight the importance of cooperative management for effective conservation
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