How the Mediterranean became the most invaded sea in the world
In October 2014, Lotfi Radaoui was roaming the shallow sandy waters near Ghannouch, a small coastal town on Tunisia’s Gulf of Gabes, with a group of local fishermen. Crossing the seagrass and seaweed, the fishermen made an unusual catch.
Entangled in their net was a species of crab, pelagic portunus or blue crab, which was not native to the area. More remarkably, the fishermen did not find a single blue crab – their nets had caught 24.
Radaoui, then a researcher at the Faculty of Sciences of Tunis at the University of Tunis El Manar, noted the discovery with interest. Little did he know, however, that a year later this non-native or alien species would become a national curse.
Soon after, the blue crab population exploded. Hakim Gribaa, a fisherman on the island of Djerba, remembers it like it was yesterday. “It was panic stations,” says Gribaa. “Crab was almost 70% of my catch and I didn’t know what to do with it.”
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Blue crabs were prolific, breeding up to four times a year with litters of 100,000 per female. This crustacean is “very aggressive”, says Gribaa – it destroys nets, and pinches fishermen and other fish. The terror caused by the crabs was such that they became known locally as “Daesh”, the Arabic acronym for the group calling itself Islamic State.
At first, the fishermen’s livelihoods were disrupted. “We had no idea,” says Fethi Naloufi, a fisheries engineer and head of the Groupement interprofessionnel des produits de la pêche in Zarzis, a public body responsible for promoting fishing and aquaculture in Tunisia. Even eliminating crab bycatch has become a challenge. “They remained piled up in the port, or they were thrown back into the sea”, says Naloufi.
The blue crab has shaken up the Tunisian fishing industry in more ways than one. But after the initial shock, it has become one of the region’s most sought-after seafoods.