Ice fishing is a great winter activity for the whole family. There are lots of nice mountain trout and char to catch. Just remember many of the lakes are regulated for water power, so make sure you know how to check if the ice is safe! You can also get some help from these websites: https://www.varsom.no/ or https://www.iskart.no/.
People who like ice fishing have a long winter to enjoy this activity. The fishing is particularly good in the spring all the way to early June. If you go high up in the mountains the lakes will be ice covered until around June 20th.
You can buy fishing licenses at https://www.inatur.no/.