Off Brazil’s São Paulo coast, the critically endangered sand tiger shark appears to have found a reproductive refuge. A new study led by researchers and divers working in the Alcatrazes Archipelago—an offshore protected marine area—documents mating in the summer and pregnancy in the winter, revealing that the species can complete its entire breeding cycle within Brazilian waters.
The findings were published in the Journal of Fish Biology by teams from the Federal University of São Paulo (UNIFESP), São Paulo State University (UNESP) and the Fisheries Institute of the São Paulo Agency for Agribusiness Technology (IP/APTA). Funding support involved FAPESP and Petrobras, reflecting the project’s focus on both conservation and ecological monitoring.
Researchers combined baited remote underwater video systems (BRUVs) with additional evidence from citizen science. BRUV deployments were conducted at multiple sites and depths, producing visual records used to count sharks, estimate size, and identify individuals based on natural body markings when possible.
Citizen divers further strengthened the dataset. In summer 2024, a dive guide captured nine sand tiger sharks on film, helping confirm that adults use the archipelago beyond what earlier reports suggested.
To move from sightings to reproductive timing, the team inferred pregnancy from female body condition visible in video. They also used a recently developed approach—previously described in the U.S.—to estimate mating dates by comparing male bite-mark healing patterns in the wild with known gestation-linked observations.
The study highlights a reproductive strategy that makes the sand tiger shark particularly vulnerable to decline: intrauterine cannibalism, in which pups consume eggs or younger siblings before birth. With typically only two pups per pregnancy and long reproductive intervals, population recovery is slow under pressure from exploitation and environmental degradation.
Because sand tiger sharks are migratory, the researchers argue that multiple protected areas in the region can function together as a conservation corridor. Continued management of fishing restrictions and habitat protection may therefore be crucial for sustaining this endangered lineage.
The work also supports broader spatial planning. In 2025, Alcatrazes was designated an Important Shark and Ray Area (ISRA) by the IUCN, reinforcing that the archipelago is not only a shelter but also a key component of regional shark conservation.
Subject of Research: Critically endangered sand tiger shark (Carcharias taurus) reproduction and habitat use in the Southwestern Atlantic
Article Title: Subtropical marine reserve as key habitats for the critically endangered sand tiger shark (Carcharias taurus) in the Southwestern Atlantic
News Publication Date: 27-Apr-2026
Web References: https://onlinelibrary.wiley.com/doi/10.1111/jfb.70479 , http://dx.doi.org/10.1111/jfb.70479
References: 10.1111/jfb.70479
Image Credits: Octávio Campos Salles
Keywords: endangered species; marine fishes; ecology; shark conservation; BRUVs; citizen science; reproductive cycle; protected marine areas
