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Found this right around day 2 or 3 of release. Its pretty comprehensive. I can confirm that if you have a suction cup pokemon in front, and the tile of water your BOBBER is in is surrounded by rocks, or non surfable terrain, you will ALWAYS get a bite when surrounded on 3 sides, with you fishing from the fourth side. I have also heard frequently that catching a pokemon breaks your chain, and that once you encounter a shiny itself, the chain breaks back to 0. I have successfully fished 2 Shiny Poliwhirls, a Relicanth and a Clawitzer. Your chance maxes out at a 40 chain at 1/200, or 0.5%, like the pokeradar.