Kill Cragjaw and take Cragjaw's Huge Tooth.
By order of people not wanting to get themselves devoured whole by a really huge fish, Cragpool Lake is OFF-LIMITS! Someone decided to up and put a huge, dwarf-eating fish in the lake.
It is strongly recommended that you stay out, however, if you are the heroic type and have a few friends around, do us all a favor and kill the damned thing! Maybe I can get some fishing done then, eh?
If you manage to actually do it, meet me back at Windshear Hold for a reward.