First record of tiger sharks (Galeocerdo cuvier) aggregation and pioneer satellite telemetry in southeastern Brazil (Ilha Grande Bay, Rio de Janeiro)

Resumo

First documented aggregation and first satellite tagging of tiger sharks (Galeocerdo cuvier) in southeastern Brazil are reported, representing a historic milestone for shark research in the Southwestern Atlantic. Despite the species circumglobally distribution, its spatial ecology in tropical coastal systems of Brazil remains a gap in current knowledge, with previous telemetry studies largely restricted to Recife-Fernando de Noronha axis. This study is based on integrated field surveys conducted in Ilha Grande Bay, Rio de Janeiro, combining systematic telemetry, visual monitoring and unmanned aerial vehicle (UAV) surveys. Recurrent shark sightings and spatial clustering in shallow nearshore waters guided targeted capture and tagging efforts. Two juvenile males (1.80 m and 2.10 m total length) were tagged with satellite SPOT tags in January of 2026, generating the first ever movement dataset for the species in southeastern of Brazil. Tracking results revealed localized aggregation patterns, repeated coastal habitat uses, and spatial overlap with urban center, navigation channels and intensively used tourist areas. The aggregation occurred adjacent to marine protected areas (MPA). The tagged sharks were named in tribute to Angra dos Reis, “Gaspar” and “Baltazar”, acknowledging the municipality’s historical and ecological connection to the study area. Findings indicate structured and recurrent habitat use rather than incidental presence, expanding regional ecological understanding. By integrating drones and satellite telemetry, this study strengthens applied marine science and provides a scientific baseline to inform marine spatial planning, adaptive management and preventive coastal governance, with potential contributions to evidence-based mitigation of shark–human interactions in Brazil and globally.