There are two areas to farm for them in my mind. The first is the SE part of the zone with the sand, following the river. They spawn up and down the area and you can also find Limrafn here as well. Word is they come out at night so you can kill two deeds with one stone here.
The second place is the island west of Tinnudur. Loaded with Salamanders. 45 locations where you have 6-10 stacked in a relatively small area. You can make loops around the island all day.