Aggressive Blue Crabs Are Invading The Mediterranean Sea

An invasion of blue crabs is taking over the Mediterranea Sea and possibly wreaking havoc on local ecosystems and economies.

Blue crabs are particularly aggressive and are known to snap fishing nets and lines with their sharp claws. They’re not docile like some marine animals, making life difficult for fishermen who are used to native fish and crabs.

Blue crabs also eat a variety of species. Those species now have to face the invasive blue crabs as predators that weren’t previously around.

Photo: flickr/James St. John

The NOAA reports that blue crabs eat “almost anything, including clams, oysters, mussels, smaller crustaceans, freshly dead fish, plant and animal detritus—and smaller and soft-shelled blue crabs.”

Beyond that, they have fewer predators in the Mediterranean Sea than they have in their native Atlantic waters, allowing them to reproduce and survive at higher rates.

Because they eat such a range of foods but have few predators (large fish, some birds, and sea turtles), blue crab populations have boomed in areas where they were previously unheard of. It’s affected not only local ecology but also the fishing economy.

Photo: Pixabay/Dimitris Vetsikas

It’s thought blue crabs initially made their way to the Mediterranean Sea on shipping vessels and quickly flourished in the new environment.

According to the NOAA, the native range of blue crabs is from the Atlantic Coast of the Americas from Nova Scotia to Argentina, including the Gulf of Mexico. They’re not native to the Mediterranean, but they’re thriving in their new habitat.

It’s believed the first blue crabs arrived in the Mediterranean as early as the late 1800s or early 1900s, around one decade after the Suez Canal opened, according to the Ibero-American Agency for the Dissemination of Science and Technology. Since then, blue crabs have been found in the Levantine basin and up through Sicily, with notable population increases around 2012 and 2014.

Photo: Pexels/Mark Stebnicki

Speaking with the BBC, Jamila Ben Souissi, a researcher on biodiversity and climate change and member of the Mediterranean Science Commission, said: “As for many invasive species, the proliferation of the blue crab has intensified with the warming of surface waters due to climate change, and with the increase of maritime traffic.”

When fishermen first started pulling up blue crabs in their catches between 2012-2014, it was a shock. The BBC reports that one fisherman, Hakim Gribaa, explained that when blue crabs started dominating fishing catches, it was “panic station.”

Photo: Wikimedia Commons

He said, “The crab represented almost 70% of my fishing catches and I did not know what to do with it.” He wasn’t alone either, and many blue crabs were thrown back into the sea, nearly destroying the fishing economy. Eventually, blue crab became a popular cuisine staple in coastal areas that previously had none of it.

Some areas are still struggling to adapt to the blue crab’s presence and it’s unclear what the long-term implications of the species invasion will be. However, many fishermen now look forward to catching blue crabs as they’ve become an in-demand food item. They’re still a nuisance when it comes to the destruction of fishing nets and line, though.

Photo: Wikimedia Commons

A study from the Ibero-American Agency for the Dissemination of Science and Technology is currently in the works as researchers aim to identify the full impact the species is having on the various ecosystems it’s invaded throughout the Mediterranean, both on an environmental level and socio-economic level.

Authorities and researchers are also collaborating to determine appropriate steps regarding the regulation and management of the species.

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