What's wrong with salmon skin?
I bought a package of frozen salmon filet pieces in Israel; they'd been imported from Poland. The package reads, in part:
מטעמי הכשרות חובה לשטוף את העור או להסירו לפני השימוש.
In my own translation:
For reasons of kashruth, there's a requirement to rinse the skin or to remove it before use.
Why? What's wrong with the skin that isn't wrong with any other part of the pieces of salmon?