To earn the Master Fisher Achievement you must catch 12 rare fish (4 Blue and 8 green) in Alik’r Desert, Bangkorai, Glenumbra, Rivenspire, Stormhaven, Deshaan, Eastmarch, The Rift, Shadowfen, Stonefalls, Auridon, Grahtwood, Greenshade, Malabal Tor, Reapers March, Cyrodiil and Coldharbour. You must also catch one rare blue fish in Stros M'kai, Kenarthi's Roost and Bleakrock. Craglorn and other DLC zones do not count toward the achievement. You can check your progress by looking at the in-game achievements under the Trophies section.
Each zone has three or four types of water and each type of water requires the correct type of bait to have the best odds of catching a rare fish. Bait can also be caught while fishing and is used in a different type of water than it is caught in. Bait, except for worms, can be farmed quickly and easily if you have access to all the zones. Here’s a breakdown:
FOUL – Fish Roe (Caught in Rivers) and Crawlers (Farmed from spiders at Hrogar’s Hold in Stonefalls)
LAKE – Minnows (Caught in Ocean) and Guts (Farmed from frogs at Sacred Leap Grotto in Grahtwood)
RIVER – Shad (Caught in Lake) and Insect Parts (Farmed around Fell’s Run in Rivenspire)
OCEAN – Chub (Caught in Foul) and Worms (Found with plants and zombies, but you’ll have to buy some of these unless you are really dedicated to farming).
For Crawlers, Guts and Insect Parts I could farm about two stacks in about 30 minutes once I got used to it. If I regularly searched Guild Traders, I could get stacks of worms for 3 to 5 thousand dollars. (And I really didn't use very many worms.)
Here is a link to The Elder Scrolls Online: Master Fisher – Fishing Guide http://teso-guides.com/the-elder-scrolls-online-master-fishe...
which I used for reference, maps of fishing spots and most of the above information. It can be assumed that any duplicate information came from that website and the credit belongs solely to the author.
The maps found at the ESO fishing guide are indispensable, but not perfect. As you understand the water types you will likely find other spots not on the map, so always keep an eye out. For example, running water is almost always river and if a dead body is nearby it is almost always foul water. Not surprisingly, however, there are always fishing spots that do not follow those rules.
Finally, ZOS kindly lets us know that if more people are fishing at a fishing hole, your odds of catching a rare fish increase (NOT including NPCs). This, sadly, is terribly misleading. I tracked all of the fishing I did and the results were mixed.
When fishing by myself I caught a Blue Fish every 153 casts over all of my solo fishing. Fishing with 1, 2 and 3 friends, I caught one every 80, 61 and 63 casts, respectively. This sounds much better, but there are two problems you face with fishing groups you do not face when fishing solo. One: Fishing holes dry out much faster so you spend more time looking for spots. Two: If you catch the blue fish you may be waiting a long time for everyone else to catch it. If I take out the duplicate blues I caught in groups, my rates drop to 110, 106 and 150 per blue, respectively. Considering how difficult it is to coordinate groups, it is suddenly clear that fishing solo is considerably better. On balance, however, fishing alone can be insanely maddening and the stats show that fishing with one partner is roughly as effective as fishing alone, so I recommend having a friend you can fish with occasionally, especially for the really tough fish.
The range of casts it took me to catch a blue fish in one type of water ranged from 9 to 972 (solo), but only a few went over 250 casts. In the cases of tough ones, trying another zone or even different day and coming back frequently helped. I always gave myself a cast, time or hole limit each solo fishing trip to keep from losing it. Anecdotally, if you have some good luck you are definitely headed for some bad luck.
Overall, it took me 94.4 hours of fishing and approximately 10 hours of farming bait to complete the achievement. A big thank you to Boozor and Harvey8irdman for putting up with me during our group sessions.
The Last note I have is about the Ocean fish in Stormhaven. It appears (currently) that the blue rare fish, Alcaire Pike, and the green fish, Dab, have their odds mixed up, so it may take hundreds of tries to get the Dab, but you may get the Pike very often. Keep at it and soon you'll have every rare fish and an even rarer title! Good luck and happy fishing!