Blacktip sharks gather every year in Piraquara de Fora Bay in southeastern Brazil. Pregnant females are among them. A recent AP News report shows how these observations are driving a conservation project in Ilha Grande Bay while changing attitudes in a local fishing community.
The focus is on the blacktip shark Carcharhinus limbatus. The “Tubarões da Baía da Ilha Grande” project examines the animals using drones and baited underwater cameras. The recordings are intended to produce reliable data about the number, whereabouts and seasonal use of the bay.
Up to 113 sharks in a shallow bay
The Important Shark and Ray Areas assessment confirms that the aggregations occur regularly and predictably. Drone surveys conducted between 2020 and 2024 counted groups of five to 113 blacktip sharks from April to mid-September. The average was 17.2 animals.
Four females were fitted with satellite transmitters between August 2023 and June 2024. One tag that transmitted longer showed that a female remained in Ilha Grande Bay for three months before moving into the open Atlantic. These data turn spectacular aerial images into a spatial picture of actual habitat use.
The expert assessment also documents two pregnant blacktip sharks from 2020 and 2024. AP reports on dozens of animals and numerous pregnant females from ongoing project work. Together with the seasonal return, this suggests that the bay plays a special role in reproduction.
Nursery, but with scientific caveats
The term nursery therefore seems appropriate and is also used in current coverage. Scientifically, however, the function of the aggregation has not yet been conclusively determined. The ISRA assessment currently lists Piraquara de Fora as an area with a regularly occurring aggregation whose function remains undefined.
This is not a contradiction to the importance of the place. Regular groups, pregnant females and proximity to the known breeding period are strong clues. However, it is still unclear whether the sharks come to the bay primarily to mate, before giving birth, to look for food or for several reasons at the same time. Only further monitoring can distinguish these functions clearly.
Warm water is probably not the only explanation
Piraquara de Fora is located near the cooling water outlet of the Angra nuclear power plant. According to ISRA, the discharge may increase surface temperatures in part of the bay by approximately three degrees. Warmer water could have physiological advantages for the sharks and thus influence their choice of location on a small scale.
However, this cannot fully explain the aggregation. Fishermen reported seasonal shark groups even before the power plant. In addition, more than 50 animals outside the direct zone of influence of the warm water were counted during drone flights. The protected location, a rich food supply and the reproductive cycle can also play a role.
From food to natural heritage
For the project, research is only part of the work. In the surrounding communities, those involved talk to fishermen and families about the ecological importance of sharks. According to the AP report, the animals used to be caught and eaten on site. Today there is a growing awareness that their regular return is a natural phenomenon worth preserving.
The Brazilian term “cação” also matters. Under this collective name, shark meat is sold without consumers always knowing the species. Targeted shark fishing is prohibited in Brazil. Unprotected species may be landed as bycatch, while threatened and specially protected animals must be released. Reliable species identification is therefore crucial for enforcement and conservation.
The project also plans environmental education in schools. Its message is pragmatic: sharks are part of the region’s natural heritage, and no shark incidents involving people are known from the bay. In addition to blacktip sharks, the work focuses on critically endangered sand tiger sharks and hammerhead sharks.
Ecotourism as an opportunity – when protection comes first
In the long term, observations from shore, boats or underwater could provide additional income for remote communities. That local benefit can make conservation more durable: people who earn lasting income from living sharks have a different incentive than a one-time catch provides.
Such an initiative would have to be developed carefully. Pregnant animals and potential breeding areas are particularly sensitive to disturbance. Small groups, clear separation distances, controlled boat traffic and rules against baiting or pursuit would matter more than maximizing encounters. Monitoring should determine when and where tourism is acceptable.
Why the bay matters now
Sharks grow and reproduce comparatively slowly. When adult females regularly use the same small coastal bay, the loss or disruption of that location can affect a population for years. Conversely, protection can be organized there in a particularly concrete way: with spatial rules, fisheries dialogue, control and monitoring that detects changes early.
Piraquara de Fora is therefore a priority for protection even before the final scientific classification. The crucial discovery is not just that there are a lot of sharks there. It is the combination of recurring groups, pregnant females and a community that begins to see the value of animals in a new way.
