Citizen science as a tool for monitoring the lionfish invasion along the coast of Bahia, northeastern Brazil

Biological invasions are among the major drivers of global socio-environmental change, with detrimental effects on biodiversity, economic activities, and human health. Among them, the rapid expansion of lionfish (Pterois spp.) throughout the Western Atlantic stands out as one of the most ecologically impactful marine invasions documented to date. In this context, citizen science, defined as the involvement of the general public in the production of scientific knowledge, has emerged as a valuable complementary approach for the early detection, monitoring, and management of invasive species. This study aims to demonstrate the contribution of citizen science to lionfish monitoring along the coast of Bahia, northeastern Brazil, highlighting the role of community participation in generating occurrence records and tracking the ongoing spread of the invasion. The study was conducted between March and June 2026 and employed a combination of science communication and outreach strategies through Instagram, e-mail, WhatsApp, and informative posters distributed in fishing communities. Participants were encouraged to report lionfish occurrences by submitting photographs, videos, associated ecological information, and, whenever available, captured specimens. All records were verified before being incorporated into a monitoring database. Citizen science was indispensable for obtaining occurrence records and biological specimens, expanding knowledge of the species' distribution in Bahia, and highlighting the importance of integrating universities and society. A total of 11 occurrence localities were documented, comprising 19 photographic records, 20 video records, and five specimens deposited in the fish collection of the Museu de História Natural da Bahia. WhatsApp was the primary platform for receiving records, which also provided valuable information on depth, substrate type, and the behavior of the observed individuals. Despite the rapid spread of the species, no effective management or control measures have yet been implemented to address this biological invasion in the region, underscoring the need for continuous monitoring and public participation.