American freshwater crayfish infest all the rice fields here in Portugal. They cause a lot of damage to irrigation and drainage ditches but the number of things that eat them is enormous. It's probably the major reason White Storks here no longer migrate to Africa in the winter. At Vila Franca de Xira, near Lisboa, when the rice is harvested in October, you can see hundreds of thousands of ibis, herons, gulls, flamingos, egrets, spoonbills, storks, waders and everything else you can think of eating crayfish of all sizes.