Field notes
The ledger is a sourced subset. Update #3 adds localization for Rammfish, Stonegnawer and Sawfin; localization by itself cannot establish a catchable habitat.
Update #4 explicitly announces new Sawfin spots, while Update #2 introduces Bloodgill spots tied to a quest. Those statements support spot existence at the patch level.
Use the detail pages to distinguish a missing field from a tested restriction.