The Atlantic Blue Crab was originally native to the western Atlantic Ocean and the Gulf of Mexico, however began to enter the Mediterranean Sea in the 1940s through ballast water, which is fresh or sea water kept on board vessels to provide stability when cargo is unloaded.

In fact, it is now listed as one of the worst invasive species introduced to the Mediterranean, and was recorded for the first time in Malta in 2016, then again later in 2021 through the recent ‘Spot the Alien’ citizen science campaign, coordinated by the Oceanography Malta Research Group  within the Department of Geosciences of the Faculty of Science.

The crab gets its name from its electric blue colour with distinctively shaped hind legs, that assist it while swimming. It is an omnivore species, feeding on both plants and animals, such as clams, mussels as well as thin-shelled crustaceans.

In 2021, marine biologist Professor Alan Deidun noted that it was too early to predict whether the Atlantic Blue Crab would proliferate in local waters like the blue swimmer crab, another invasive species that has raised concerns. This uncertainty highlights the importance of initiatives like the ‘Spot the Alien’ campaign to monitor and address the impact of invasive species in our marine ecosystems.

Have you ever seen an Atlantic Blue crab while snorkelling or diving?