You came to us a novice, and now look at you! A fishing master! None of us, least of all the fish, expected you to come this far. Most of us placed wagers that you'd be dead already.
Long story short, you only have one more step before becoming a true fishing legend, and helping me get out of debt. You will need the Argonian rod I gave you earlier, as well as the Alik'r rod from Viriya.
Here is a list of the rarest catches in all of Skyrim:
Angelfish
Angler
Lyretail Anthias
Scorpion Fish
Be sure to read the fifth, and final, volume of Fishing Mastery to learn the secrets of their whereabouts, and the rods one must use to catch them. Should you succeed, I have the perfect gift for someone sharp like you to represent your mastery of fishing. It will help you skin your catches as well as the occasional bandit. Best of luck.