Or rather red swamp crayfish (Procambarus clarkii – known in Catalan in cranc vermell americà, hence in title). It is an introduced species that has displaced the native white-clawed crayfish (Austropotamobius pallipes), outcompeting it and carrying a disease to which they are resistent, but the native crayfish are not, so you won’t find them in the same stretch of river.
As volunteers of CEN we’ve spent a few nights (crayfish usually come out at night) removing this invasive species, and we did that on Friday night too, with Jesús Ortiz, the president of CEN, and a few other volunteers. It was very cold and wet, but luckily we wore waders and long rubber loves to avoid getting wet (I did reach a bit too deep on one occasion, and got a glove filled with water!), but we had a very good time. Made even better with good company.