The blue crab, can we eat the invader?

24-08-2018

The blue cracker is a newcomer species that is already present in two of the most important wetlands in Catalonia, the Ebro and Llobregat deltas.


The blue crab (Callinectes sapidus) is a relatively recent invasive species that has spread very quickly along the Catalan coast. It was first mentioned in the Delta de l'Ebre in 2012. In just 6 years it has spread over much of the coast and has risen up the river Ebro to the Xerta dam, which shows a great adaptability to salinities. very different. It can reach 1 kg in weight, although the normal is 300-400 g. It is also present in the Llobregat Delta and the Aiguamolls de l'Empordà. These crabs grow at temperatures between 15 and 30ºC, below 10ºC they cannot move and if they fall below 5ºC they cause hibernation. For this reason, they are abundant in spring and summer. Salinity does not condition its distribution after the larval period.
They have the last pair of fins in the form of fins and are active swimmers. They reach sexual maturity in the 2nd year. Females only spawn once in a lifetime, but can lay 2 to 8 million eggs. Larvae require a minimum salinity of 20 ‰, but juveniles and adults can live from freshwater to hypersaline.
It is known to eat mollusks, crustaceans and fish and is a large predator. It was filmed while eating mussels and has been the reason to stop raising clams in the Ebro Delta. The places of origin are conditioned by the abundance of mussels, clams and oysters. On the other hand, it has great gastronomic value, both in its natural distribution area and in the Ebro Delta, where some restaurants have already included it in their menu. For the first time, this year the Generalitat has granted fishing rights for this species.

From an ecological point of view its appearance is too recent to know what consequences it will have. Similar to what has happened to the European green crab (Carcinus maenas, very similar to the Mediterranean), which has become an invasive species in some areas of North America, but has been slowed by the blue crab in areas where this is abundant, it is intuited that it may be a potential competitor and predator of the native Mediterranean green crab (Carcinus aestuarii). It has also appeared at the mouth of the Guadalquivir. There, the invasive red crab (Procambarus clarkii) is exploited economically, and shellfish gatherers fear that it could quickly wipe out the industry. Closer to home, it appears to be a voracious consumer of another deltaic invader, the apple or apple snail (Pomacea maculata). In the United States, it has also been seen attacking another species much feared in the Ebro, the zebra mussel (Dreissena polymorpha), although it has not yet been found in our country. It does not appear to eat only invertebrates and fish, as remains of viper have been found devoured by the blue crab. Presumably it will also put pressure on amphibians and aquatic insects. The changes and decouples that it will be able to cause in the trophic networks of our wetlands are unknown.

More information:
VIDEO El cranc blau remunta el riu Ebre a tota velocitat
La llotja de la Ràpita comercialitza el cranc blau, el nou invasor de la mar de l’Ebre
El Departament d'Agricultura atorga les primeres autoritzacions per a la pesca de cranc blau a les Terres de l'Ebre
“El cranc blau ha arrasat el cultiu de cloïssa a la badia del Fangar”
El cranc blau americà s’introdueix als espais naturals del Prat
Indian River Lagoon Species Inventory: Callinectes sapidus Rathbun, 1896
Biotic resistance to invasion: native predator limits abundance and distribution of an introduced crab
Biotic resistance on the increase: native predators structure invasive zebra mussel populations
The trophic position of the Atlantic blue crab Callinectes sapidus Rathbun 1896 in the food web of Parila Lagoon (South Eastern Adriatic, Croatia): a first assessment using stable isotopes

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