A Remarkable Dolphin Day in the Greater Bazaruto Seascape

On 11 September 2026, BCSS researchers and participants in our Scientific Training Program (STP) travelled south for one of our weekly oceanic expeditions, conducting spatial mapping of marine megafauna across the Greater Bazaruto Seascape.

The survey took the team into the sheltered coastal waters around the São Sebastião Sanctuary, where they recorded an exceptional seven separate encounters with Indo-Pacific bottlenose dolphins (Tursiops aduncus).

Group sizes ranged from approximately four to 20 animals, producing a cumulative estimate of almost 90 dolphins across the day’s encounters, including at least four calves.

Seven Encounters in a Single Survey

Throughout the day, researchers documented dolphins resting, socialising and foraging within the survey area.

The shallow, protected waters around São Sebastião provide valuable habitat for this coastal dolphin species. Observing several different behavioural states within the same area offers insight into the diverse ways dolphins may use this habitat, including feeding, recovery, social interaction and the care of young.

One particularly memorable encounter involved a calf that began bow-riding alongside the BCSS research vessel.

After several minutes, an adult, possibly its mother, joined the calf. The pair rode the bow together before eventually changing direction and moving away.

Distinctive dorsal-fin markings photographed during the 11 September survey. Nicks, notches and scars can help researchers recognise individual Indo-Pacific bottlenose dolphins during future encounters. Images: Ekaterina Kalashnikova / BCSS

Identifying Dolphins by Their Dorsal Fins

Indo-Pacific bottlenose dolphins are naturally inquisitive and may approach boats or divers, providing researchers with opportunities to photograph individuals.

Much like the flukes used to identify individual humpback whales, dolphin dorsal fins can provide a distinctive visual record.

Nicks, notches, scars and other features along the dorsal fin can allow researchers to distinguish one dolphin from another and compile photo-identification catalogues.

By comparing photographs collected during different surveys, researchers can investigate whether individuals are encountered repeatedly and begin examining patterns of site fidelity, movement, habitat use and social association.

Indo-Pacific bottlenose dolphin dorsal fin photo-ID. Images: Ekaterina Kalashnikova / BCSS.

One Dolphin Stood Out

One individual encountered during the survey had a markedly truncated dorsal fin.

The cause cannot be determined from observation alone. Possible explanations could include a previous unsuccessful predation attempt or an interaction with fishing line or other fishing gear.

Whatever its origin, such a distinctive feature may make this individual particularly recognisable during future surveys.

If photographed again, researchers may be able to connect those encounters and begin building a longer-term record of where the animal is seen and how it uses the Greater Bazaruto Seascape.

Encounters such as this can provide valuable records for collaborative research into dolphins across the region. Image: Ekaterina Kalashnikova / BCSS.

Why Long-Term Monitoring Matters

Indo-Pacific bottlenose dolphins have a strong association with shallow coastal environments, which can also place them in close proximity to human activities.

Potential pressures across their range include incidental capture and entanglement in fishing gear, habitat degradation, coastal development, pollution, vessel disturbance and changes in prey availability.

Long-term information remains limited for many local dolphin populations. This makes consistent monitoring and the accumulation of comparable records particularly valuable.

A single survey provides a snapshot. Repeated surveys allow those snapshots to become a dataset.

Indo-Pacific bottlenose dolphin (Tursiops aduncus). Images: Ekaterina Kalashnikova / BCSS.

Building a Picture of the Greater Bazaruto Seascape

BCSS conducts spatial-mapping expeditions weekly, bringing researchers and Scientific Training Program participants together to record marine megafauna, behaviour and environmental conditions throughout the Greater Bazaruto Seascape.

The seven dolphin encounters recorded on 11 September made for an exceptional day in the field, but their scientific value extends beyond the number of animals observed.

Each location recorded, behaviour documented and identifiable dorsal fin photographed contributes another piece to our understanding of how marine species use this diverse and dynamic region.

Over time, these observations help build the long-term evidence needed to understand and support the conservation of marine life across the Bazaruto seascape.

Learn more about our STP programme

More information:

For questions about this article, please contact: 

Ekaterina Kalashnikova, Bazaruto Archipelago – Ocean Observatory Bazaruto Center for Scientific Studies ekaterina.kalashnikova@bcssmz.org  

To get in touch and collaborate with our research Center , please visit https://bcssmz.org/logistical-support-consultancy/  

To learn more about our Scientific Training Program, please see https://bcssmz.org/scientific-training-program/  

Bazaruto Center for Scientific Studies
Host of the first permanent Ocean Observatory focused on multi-ecosystem time series research in Africa, the Bazaruto Center for Scientific Studies (BCSS) was established in 2017 as an independent, non-profit organisation with a mission to protect and support the fragile ecosystems of the Bazaruto Archipelago, Mozambique. The research station is located on Benguerra Island, off the coast of Mozambique.
Legs Brands

Recent news

Scroll to Top

Stay in the know

Receive monthly updates about our research, projects, new papers and spectacular wildlife encounters, straight into your inbox.Â