Fishing along the coast (saltwater) is for free ofcourse...and the possibility of catching fish is very good. When fishing in freshwater areas (especially in the mountains) you need to buy a daylicense. It might be obtained at the local gasstation,food store or help yourself box. Recommending using worms for bait and not any weird lures (bought in the EU area made in China..

The mountaintrout is very good to eat and very shy...so approach these lakes very tenderly...Put som led at the end of the fishing line...a hook 30 cm above and put on a lot of worms and throw it all out ...when the line is stretching or moving in any way.....then pull back and dinner is alomost served. It tastes well if you fry it in a pan together with "rømme" and ofcourse a cold one to drink leaning back on your GS surrounded by total silence and enormous mountains all around you...
Good luck...