A recent scientific study has shown that the Alcatrazes Archipelago off the coast of the Brazilian state of São Paulo plays a crucial role in the entire reproductive cycle of the critically endangered sand tiger shark (Carcharias taurus). Contrary to earlier assumptions that these sharks migrate to the warmer waters of southeastern Brazil only for pregnancy and birth, new findings show that they also mate there.
Until now, sand tiger sharks were thought to mate in the colder waters of Argentina, Uruguay and southern Brazil. The research, published in the journal Journal of Fish Biology, was carried out by Unifesp, Unesp and the Instituto de Pesca and supported by FAPESP and Petrobras. It refutes that assumption. According to the study, the sharks are present in the Refúgio de Vida Silvestre do Arquipélago de Alcatrazes in both winter and summer and complete their entire reproductive cycle in Brazilian waters.
New insights from extensive observations
The researchers used baited remote underwater stereo-video systems (BRUVs) as well as direct observations by scientists and citizen scientists (divers) to record the sharks at depths between 2 and 50 meters. This method made it possible to document the animals’ behavior over longer periods. Ana Clara Athayde of Unifesp commented on the findings: “We have shown that they are not only here in winter, as previously assumed, but also in summer, and that they complete their entire reproductive cycle in Brazilian waters.”
Fabio Motta, also of Unifesp, emphasized the importance of the new records: “There are historical records of sand tiger shark bycatch off the coast of São Paulo, but there was no scientific documentation until ours in Alcatrazes in winter 2022.” These first scientific observations in the archipelago are crucial for understanding the species.
The Alcatrazes Archipelago, designated by the IUCN in 2025 as an Important Shark and Ray Area (ISRA), functions as an important ecological corridor for these slow-reproducing sharks. Sand tiger sharks are classified globally as vulnerable, but in this southwestern Atlantic region they are considered critically endangered, mainly because of historical overfishing. Their reproductive rate is very low: only two young per pregnancy, which lasts nine to twelve months and is characterized by intrauterine cannibalism.
