El arroz y el cangrejo rojo de Isla Mayor Food and drink · Isla Mayor, Comarca Metropolitana de Sevilla, Seville With more than 9,600 hectares of rice paddies, Isla Mayor produces a good part of the rice from the Guadalquivir marshes. The American red swamp crayfish, introduced in 1974, became an economic resource and a local dish, though today it makes up more than half the diet of some twenty bird species in the marshes. 1974 (introducción del cangrejo rojo) Photo: 19Tarrestnom65 (CC BY-SA 4.0) What to see and do in Isla Mayor