I think jorb wants to keep what you're actually asking secret, but I have my own personal theory on how fishing works - there's actually three key numbers.
- Node Coefficient:
The most mysterious value. Not only changes over time, but also decreases the further away you get from the centre of the node, a point which itself shifts over time.
- Tackle Coefficient:
Generated randomly at world's start for each Line/Hook/Lure/Fish combo and remains constant.
Each possible combination is independent, so even if Shoreline/Bone/Rock Lobster and Bushcraft/Bone/Woodfish are both very good at catching Salmon, Bushcraft/Bone/Rock Lobster could be awful.
- Lure Coefficient:
Generated randomly at world's start for each Lure/Fish combo and remains constant.
Chance to Bite is the product of Node Coefficient and Tackle Coefficient. Failing this roll then starts a new roll to decide if you get a piece of garbage/a random part of your tackle breaks/nothing happens.
Chance to Land is simply Lure Coefficient. Failing this roll always destroys your lure.