French fishers unite against invasive American blue crab

A group of fishers in the south of France have banded together to limit the spread of the American blue crab across Occitanie's waters. 

The crab, officially classed as an invasive species in France, has become present in a number of lagoons and waterways across the country.

First spotted in the Mediterranean in the Adriatic around the 1940s, and likely making its way across the Atlantic in ship ballast water, the crustacean has slowly spread across the Mediterranean, and can be found everywhere from the Po Valley in Italy to the Ebro in Spain.

In France, they are found in various coastal shores and lagoons in Occitanie, particularly around Pyrénées-Orientales and Aude.

Numbers have exploded in the last five to 10 years, with the species becoming dominant in many waters.

It is noted for its voracious appetite, alongside its ability to travel up to 15 kilometres per day, making them hard to track or keep confined to a single area.

The crab’s arrival has not only affected the fishing industry by eating into daily catches (oftentimes using powerful claws to cut through nets to feast on eels and fish) and devastating oyster and mussel farms, but via a long-term impact on the ecosystem.

The crabs will eat anything from other crustaceans to algae, and its only natural predator in the Mediterranean is octopus, which are rarely found in inland lagoons.

Females lay up to eight million eggs

Fishermen across the Occitanie region are now taking matters into their own hands.

The ‘blue crab Sentinels’ (Sentinelles du Crabe bleu) project across the region looks to work with fishers to reduce numbers.

They are actively seeking out female blue crabs to kill them and so prevent them from breeding. Each female can lay up to two million eggs, doing this four times during the mating season.

Fishers will also report their catches of blue crab to authorities to track their numbers, to ensure the spread of the animal is limited.

The more crabs that are present the more dangerous they are, with smaller levels of the animal seen as more manageable. 

Scientists remain puzzled by the sudden explosion in blue crab numbers, but point towards climate change as a possible explanation.

Another explanation, which may also explain why the crabs stay away from certain lagoons even when they could otherwise easily reach them, is the salinity of water.

The animals seem to thrive in areas where water is less saline, with lagoons and river valleys seeing salt levels vary considerably over the year. 

While many regions where the crabs are present, including Occitanie, may suffer from droughts that reduce water levels and make them more saline, they are equally at risk of intense rain and freshwater intrusion from flooding.

Crab on the menu? 

Regions across the Mediterranean have tried several methods to deal with the invasion, including culling campaigns and the introduction of predators, so far to little avail.

The next strategy on the list is to directly catch the crabs and turn them into a profitable resource – increasingly important for the fishing industry as the crabs limit the supply of other foodstuffs. 

In Italy, blue crab fishing around the Po delta is set to turn into a €20 million turnover industry as fishers get the green light to engage in intensive fishing campaigns.

The plentiful nature of the blue crab, the fact it is safe to consume, and alleged good taste are all factors pointing towards success.

The difficulty however lies in finding a buyer. Unlike in the US where blue crabs are commonly found on the menu in restaurants, with varieties like the Chesapeake blue crab in particular demand, European palettes have yet to embrace the food.   

Fishers in Italy currently sell the crab for €1.30 per kilogram to bulk buyers in Sri Lanka, who use the meat in various goods exported to Asia, where there is more of a taste for the crustacean.

This price is around one tenth that of clams – one of the native species on the voracious crustaceans’ menu – and comes with significant ecological cost of its own. 

In France, the crab sells for around €2 per kilogram, with fishers feeling it is hardly worth going out to capture the animals – except they are everywhere in the water and hard to miss. 

Locals and restaurants in France and Italy are being encouraged to use the crab, but remain wary and prefer to stick to classic foods such as mussels or oysters, grown for centuries.

Even where crab is used, people prefer native European species, such as brown or spider crabs. 

A coordinated effort is required to tackle the proliferation, therefore.