A piece of salmon was purchased at a non-kosher fish store and cut initially with a non-kosher knife. It was washed off afterwards in the home, but not scraped. It was then cooked (grilled, so likely no shishim). 1) is the scraping an issue b’dieved if it was washed? 2) is the chiyuv to scrape d’rabbonon or d’oraisa? 3) is it at all called a safek whether the knife was clean if it was in the fish store, or is it not a “safek maalya” but rather likely that it was used and not clean? I suppose the salmon could have been cut first thing in morning, could have been cut with knife only having been used with kosher min of fish etc.
Even if the salmon was cut with an unclean knife, since it was washed off before use only a residual amount of treif particles remained on the knife which are botel in shishim.
Y:D 91 Taz 2, 96 Shach 17,