In reply to Phill Mitch:
The Rio Deva and other Picos rivers have a run of salmon and native brown trout. Check this link for details of fishing licences :
http://www.dgmontes.org/solicitudes_inf.htm#pesca
I last fished in the Picos in 1996, when obtaining a licence was troublesome. If it's similar to Aragon, you submit your application on-line and receive your licence by mail, then validate with payment in an authorised bank. The basic licence is very inexpensive.
If you fancy a beach, with rocks to play around on, try Pechon, very near to the estuary of the Deva.