I just spent a while fishing for the following quest:
Not only did I not catch the carp, I used up 2 stag eyes. Almost 50 casts and I only caught 4-5 fish (one of those being old crafty...how the hell do I actually get him, after years of trying/failing on live, and not get the carp?). What I did catch was 2 "The 1 Ring"s, lots of armor, weapons, bags, recipes and enchantments.
Something needs to be changed in the loot tables so not only the carp can be caught but fish period.