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.
Saturday morning me and Mika got our welly boots on and went to a small workshop to look at the biodiversity in Francolí river, just outside of Tarragona. Apparently it is the most polluted river in Europe, so in terms of biodiversity is one of the lowest as low biodiversity corresponds with high pollution in lakes, rivers and ponds. Only the most robust species are able to survive.
But there were still some things to be found, like the American crayfish (not the native Iberian crayfish), dragonfly larvae, damselfly larvae, mayfly nymphs, a frog and a tadpole, and an air breathing aquatic beetle that doesn’t look aquatic, plus various other little creatures. I don’t know how many times I’ve done surveys in water habitats like this, taking a net and tray and seeing what there is, but it’s always very interesting. The main difference was that it wasn’t in English but Catalan, which surprisingly I could catch some of.
The American crayfish is causing problems with the native Iberian Crayfish, since it is more competitive and more immune to a fungal disease that is killing of the Iberian crayfish. We’re lucky enough to have a small colony of Iberian crayfish in a stream on the land, and I hope it remains like that for a long time to come.