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Invasive blue crabs are taking over the Mediterranean Sea

Coastal towns near the Mediterranean are grappling with an invasive sea species brought to their waters by international shipping boats. Dealing with this new inhabitant might mean serving them up on thousands of plates across Europe โ€“ if only a local appetite for them will grow.

International trade is causing hundreds of animal species to find homes in parts of the world they would have never reached otherwise.ย  This is particularly true for certain marine animals.

As shipping vessels depart from ports, their gigantic engines suck up gallons of seawater known as ballast water. Microorganisms, algae, and fish eggs are also brought along for the ride.

This water โ€“ and the life within it โ€“ is stored temporarily and offloaded when the boat arrives at its next destination.

Over the last few decades, hundreds of species have been popping up in the Mediterranean due to the release of ballast water. This may not seem like a bad thing until one of those species is deemed invasive to its newfound environment.

Around 2017, one of the 900 unusual species spotted in the Mediterranean Sea was the Chesapeake or Atlantic blue crab. Itโ€™s usually found exclusively on the East Coast of the US or in the Gulf of Mexico where it is considered a culinary delicacy.

Its continued presence wouldnโ€™t normally be a standout issue for Europeans, however, the blue crab has been documented destroying the majority of living species in its wake.

 

Not picky eaters, the blue crabs feed on mussels and oysters which they pry open with their sharp claws. Theyโ€™re also known to devour other smaller crabs, fish, and eels living along the coastline.

This crustaceanโ€™s varied and insatiable diet has destabilised the Mediterranean food chain over time. Even local birds have been seen hunting in other locations because โ€˜thereโ€™s no food leftโ€™ in the ocean for them.

Meanwhile, fishermen seeking their regular catches are facing difficulties โ€“ but are having no problem hauling in these new crabs. One fisherman reported catching 30 kilos in December, saying โ€˜we donโ€™t know what to do with them.โ€™

In America and Canada, blue crabs sell at around $90 per kilo. But in Europe, the appetite for this creature hasnโ€™t exactly caught on yet. France is selling them for as little as โ‚ฌ2 per kilo. A steal if you ask me.

Not to be the bearer of bad news, but the current situation may only be exacerbated as Mediterranean waters warm up over summer.

Native species are having trouble coping with this change, while the Atlantic blue crab is thriving. It reproduces faster in warmer waters, with females laying up to 2 million eggs in one go.

 

The blue crab can live for up to four years and can grow up to 23 centimetres wide. Its pincers are its best weapon and fishermen say that they aren’t afraid of humans. A quick snap of one often results in a trip to the nearest A&E.

Dealing with the disruption of local environments will be the focus of international trade regulations in years to come. So far, it looks like large boats will be required to have systems that prevent the transfer of new species via ballast water by 2024.

Thereโ€™s already a technique currently being explored. It will involve passing filtered ballast water through UV lighting to neutralise living species picked up as boats depart and enter ports.

Hopefully, this will prevent the disruption of marine ecosystems in the future. In the meantime, Europeans will have to broaden their palettes to include the Atlantic blue crab.

Bon appetit !

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