"We want the law to go back to what it was three years ago," João Cortez, president of the association Important Oásis, promoter of the protest, told reporters.

According to the official, the crayfish caught in the dams of Baixo Alentejo is sold to Spanish companies, which have processing factories, and later exported to countries such as Sweden and the United States.

If there are no answers to the fishermen's demands, the president of the association Important Oásis revealed that a new protest is already scheduled for 15 August.

Louisiana's red crayfish first entered Portugal in 1979 and they have spread over at least 11 hydrographic basins in the country: Douro, Leça, Vouga, Mondego, Lis, Ribeiras do Oeste, Tejo, Sado, Mira, Ribeiras do Algarve and Guadiana.

It is a voracious predator of amphibians, insects and plants.