Tracing yellowbar angelfish invasion pathways in the SW Atlantic using otolith chemistry

A single male individual of the nonnative yellowbar angelfish Pomacanthus maculosus was sampled in a marine protected area in Brazil, southwestern Atlantic, in 2019. To investigate possible pathways of invasion, we analysed otolith chemistry and macrostructure under three hypotheses: (1) early-life natural dispersal, (2) dispersal during the adult stage, and (3) anthropic introduction. Species identity was confirmed by DNA barcoding, and gut content analysis was performed to explore ecological implications. An individual of the same species was recorded during a SCUBA diving survey at the same site 420 days prior to the capture, potentially corresponding to the same individual. By integrating the occurrence record, social context, and otolith chemistry, we concluded that the introduction most likely resulted from aquarium trade release. Genetic evidence suggested potential origins from the Indian Ocean or the Red Sea. Gut contents were dominated by sponges (86.9%) and algae (6.0%), indicating potential negative impacts through dietary overlap with native congeneric species. Although several studies suggest aquarium release as a possible introduction route, none have explicitly assessed this pathway using empirical tools. Our findings highlight the value of otolith chemistry as a forensic tool for elucidating introduction pathways and advancing the understanding of fish biological invasions.