When you look at the individual fisheries there are a lot of helpful links on which give you bespoke individual info about the particular waters. Spot on (grovel to Monk again)
Gerry,
Its a right pain. First you go to a bank and pay your "tasas de pescar"....tax for fishing. You will need your pasport and its a bit tricky filling in the application form if you cant understand it.
It only costs a few Euros but only covers you for that region.
Then you take your recipt to their EA type place where they will give you your licence. Its called the "Consejeria de Agricultura y medio ambiente".
Not all banks will have the required forms, I once had to try 4 before I dropped lucky.
Be aware that each region is slightly different in its approach with Andalucia (Seville) having a bit of a reputation for being tricky sometimes.
Dont be tempted to fish without one though the "Guarda Civil" dont mess about.