Abstract
The blue crab is an invasive species that has rapidly spread along Mediterranean coasts, threatening marine ecosystems. Exploring natural ways to control its population could help reduce these impacts. In this study, we investigated the functional size preference and feeding rates of two native predators-the common octopus and the loggerhead sea turtle-when feeding on blue crabs. In aquarium experiments, predators were offered crabs of different sizes under controlled conditions to assess whether they preferred certain sizes and how much they could consume in a day. Both species consumed substantial amounts of blue crabs: octopuses fed only on soft tissues, whereas turtles ingested whole crabs, including the exoskeleton. Octopuses exhibited shorter handling times for small crabs, although neither predator showed a marked size preference. Our findings suggest that, particularly octopuses, thanks to their abundance and feeding efficiency, could contribute to limiting invasive crab populations and support ecosystem balance.
The rapid spread of the invasive blue crab (Callinectes sapidus) in Mediterranean coastal ecosystems poses ecological and socio-economic challenges, highlighting the need to explore natural control mechanisms. We conducted controlled aquarium experiments to assess the functional size preference and feeding rates of two native Mediterranean predators: the common octopus (Octopus vulgaris) and the loggerhead sea turtle (Caretta caretta). Two sets of trials were performed: (1) size preference experiments, in which individual predators were simultaneously offered crabs of varying sizes; and (2) ad libitum feeding experiments to estimate daily consumption rates. Octopuses consumed only the soft tissues biomass (STB, similar to 54% of total crab biomass), reaching maximum intake rates of 454 +/- 71 gWW.d(-1) in adult individuals. Sea turtles ingested whole crabs, including the exoskeleton, with total consumption rates up to 815 +/- 592 gWW.d(-1) of total biomass (TB) in adults. Subadult octopuses exhibited shorter handling times for small crabs, although neither predator showed a statistically significant size preference. Our findings indicate that both predators can consume substantial amounts of blue crab biomass, but O. vulgaris-due to its higher feeding efficiency and ecological abundance-might play a more prominent role as a natural biocontrol agent. These results provide valuable insights for integrated management strategies aimed at mitigating the ecological impact of C. sapidus in the Mediterranean.
