First Records of Wild Octopus (Octopus vulgaris) Preying on Adult Invasive Blue Crabs (Callinectes sapidus)

The Atlantic blue crab, Callinectes sapidus, has rapidly expanded its invasive range ubiquitously in the Mediterranean Sea, posing ecological threats to native ecosystems. In its native habitat, the crab plays a crucial role in the ecosystem, but in invaded areas, it lacks natural predators. This has led to rapid expansion, highlighting the need to monitor and understand biological interactions with the native community. This study reports, for the first time in the wild, the predation of the invasive blue crab by the common octopus, Octopus vulgaris, in the Mediterranean Sea. Three sequences (two videos and a photography series) recorded by two spearfisherman (observation 1 and 2) and a recreational SCUBA diver (observation 3) are described. This article highlights the importance of native predators in influencing the expansion or control of invasive species. Additionally, it showcases the capacity of a versatile predator (the octopus), to serve as an ally alongside the fishing strategy, suggesting a novel perspective for ecologically sustainable management, in a context of low native predators of the blue crab. The collaboration with citizen scientists proves crucial in expanding our understanding of predator-prey dynamics and ecological interactions, underlining the need for continued partnerships between researchers and society for effective invasive species management.