Managing the growing number of non-indigenous species in the Mediterranean Sea

Hundreds of non-indigenous species have invaded the Mediterranean Sea over the past few decades. Today, they are altering local biodiversity, disrupting fisheries and aquaculture throughout the region. But some of these invasive species are generating commercial opportunities for the fishing and aquaculture sector. 

The Ebro Delta is Catalonia's largest wetland, home to hundreds of aquatic species and a place with a long fishing tradition. 

For centuries, the local association - 'Brotherhood of San Pere' - has been fishing in the largest lagoon, the Encanyissada. But a few years ago, their usual catch suddenly dropped. Instead, they found a surprising newcomer: the blue crab, a ferocious North American crustacean that has invaded the area, decimating local species.

"What happens is that it eats all the young species, it eats all the eggs, and destroys our nets! It eats everything! It ate all the endemic fish here," explains local fisherman Raul Paulino.

With other species largely gone, local fishermen switched to catching the blue crab.

"In the first few years, they were abundant but weren't highly-priced. Now it's the opposite - fewer but worth more. But hey, that's the fisherman's life," Raul says. 

Local researchers say allowing professional fishing of these new crabs is the best hope of stopping an explosion in the population.

Catalonia has put in place a special co-management committee with the aim of providing better scientific advice, improving the capture and streamlining blue crab trade through the fishing market. 

This part of Spain is being closely watched by other regions, increasingly affected by the blue crab invasion. 

The General Fisheries Commission for the Mediterranean has launched a regional research programme