[Stefan-A]

I think I read on another forum that it's not okay, but I haven't been able to confirm it through other sources.

edit: Cod is on the list of species reported not to contain thiaminase.

Nothing needs to be done, if it's okay. The "only" difference between freshwater and saltwater fish, is how they regulate the salt levels in their system, so unless the meat has been soaking in saltwater, there's really nothing that needs to be done.