The French connection: Multiple records of Strait of Gibraltar killer whales (Orcinus orca) (2003–2023) in the Bay of Biscay, France

Documenting species occurrence and distribution patterns is fundamental for effective conservation strategies, particularly for endangered species facing various threats. Killer whales (Orcinus orca) are distributed worldwide, yet some populations, such as the critically endangered Strait of Gibraltar subpopulation, lack comprehensive distribution data. This study focuses on documenting the occurrence of Strait of Gibraltar killer whales along the French coast of the Bay of Biscay using twenty years (2003–2023) of scientific and citizen science data. Analysis of 34 sightings revealed seasonal patterns, with most sightings occurring between June and November. Also, killer whales are observed more often in the area since 2015. Photo-identification methods allowed for the identification of 11 individuals, eight of which were recaptured in Spanish and Portuguese catalogs, confirming their affiliation with the Strait of Gibraltar subpopulation. Some individuals have been sighted over several years, regularly travelling together, suggesting potential site fidelity to the Bay of Biscay. Overall movement patterns showed associations with Atlantic bluefin tuna distribution. However, disruptive behaviors observed in some individuals highlight conservation challenges. This study provides novel insights into the distribution and movements of a critically endangered killer whale subpopulation, informing future conservation efforts in the region.