The Fisher and Crab Traps are part of Bruno’s awesome Archipelago Biome Mod! The issue might (or might not) be related to ACE but to make sure it’s nothing else (or another mod), try loading your save without ACE (it will break a lot of things, but should load) and see if your fisher remains stuck.
Alternatively, it could be some other things like placement, etc… But maybe you should give more details there 