Pokemon Red/Blue Fishing Guide

Because I didn't really know how to work this into the actual walkthrough.

Old Rod (Obtained in Vermillion City)
Magikarp: Pallet Town, Viridian City, Cerulean City, Vermillion City, Vermillion Harbour, Celadon City, Fuschia City, Safari Zone, Seafoam Islands, Cinnibar Island, Indigo Plateau
Routes; 6, 10, 11, 12, 13, 17, 18, 19, 20, 21, 22, 23, 24, 25

Good Rod (Obtained in Fuschia City)
Poliwag: Pallet Town, Viridian City, Cerulean City, Vermillion City, Vermillion Harbour, Celadon City, Fuschia City, Safari Zone, Seafoam Islands, Cinnibar Island, Indigo Plateau
Routes; 6, 10, 11, 12, 13, 17, 18, 19, 20, 21, 22, 23, 24, 25
Goldeen: Pallet Town, Viridian City, Cerulean City, Vermillion City, Vermillion Harbour, Celadon City, Fuschia City, Safari Zone, Seafoam Islands, Cinnibar Island, Indigo Plateau
Routes; 6, 10, 11, 12, 13, 17, 18, 19, 20, 21, 22, 23, 24, 25

Super Rod (Obtained on Silence Bridge, south of Lavender Town)
Psyduck: Route 24, Route 25, Cerulean City, Safari Zone
Poliwag: Pallet Town, Viridian City, Route 22
Poliwhirl: Route 10, Celadon City
Tentacool: Pallet Town, Viridian City, Routes; 12, 13, 17, 18 
Slowpoke: Route 10, Celadon City, Safari Zone
Slowbro: Route 23, Cerulean Cave
Shellder: Vermillion City, Vermillion Harbour, Seafoam Islands, Cinnibar Island, Routes; 6, 11, 19, 20, 21
Krabby: Cerulean City, Vermillion City, Vermillion Harbour, Fuschia City, Safari Zone
Routes; 6, 11, 12, 13, 17, 18, 24, 25
Kingler: Route 23, Cerulean Cave
Horsea: Seafoam Islands, Cinnibar Island, Routes; 19, 20, 21
Seadra: Route 23, Cerulean Cave
Goldeen: Cerulean City, Fuschia City, Safari Zone, Seafoam Islands, Cinnibar Island
Routes; 6, 12, 13, 17, 18, 19, 20, 21, 22, 24, 25
Seaking: Route 23, Fuschia City, Cerulean Cave
Staryu: Seafoam Islands, Cinnibar Island, Routes; 19, 20, 21
Magikarp: Fuschia City, Routes; 12, 13, 17, 18
Dratini: Safari Zone