As I was skilling up in fishing, in a zone where I'd get a lot of lost fish I'd slap on a nightcrawler or some other lure, and that would reduce the numbers of lost fish very significantly, also helping me skill-up faster in those areas. Undead mobs generally drop them fairly regularly (about 15% of the time, look up nightcrawler on this site to see which mobs specifically drop them and which would be best for you to hunt). In 4 or 5 levels I'd recommend the two ruins in Stranglethorn Vale. I got a good amount of them as I was finishing a couple of quests there.
Gorluk
49 Troll Warrior on Garona