A rare Mediterranean vagrant: Makaira cf. nigricans (Carangiformes: Istiophoridae) recorded off the Ebro Delta

The Atlantic Blue Marlin Makaira nigricans is a large,migratory billfish generally absent from the Mediterranean. On 18th May 2024, video footage of an individual hooked during recreational trollingapproximately 5 nautical miles off Sant Carles de la Ràpita (Ebro Delta,Spain) was provided to the authors by a recreational angler througha citizen-science contribution. The fish was visually estimated at ~2.5 m TL and ~100 kg and was cautiously identified as M. cf. nigricansbased on photographs and video footage. Because the individual was released and not examined directly, several diagnostic characters couldnot be assessed in detail. Nevertheless, the identification was supportedby the presence of key diagnostic traits visible in the images, includinga robust, round-section rostrum, pectoral fins capable of being folded back against the body, and a first dorsal fin lower than body depth with a long base. This observation potentially represents the third scientifically documented Mediterranean record, the first from the western basin, and the first in several decades. Given location and oceanographic setting, awest-to-east entry via the Strait of Gibraltar is more plausible than Suezingress and accords with the species’ preference for offshore waters andthermal/productivity gradients. There is no evidence of local residency or reproduction, but such vagrant occurrences warrant attention amid climate- and circulation-driven shifts.