Temperature at which to pickle herrings
Herrings should be pickled in refrigerator. Before the pickling solution fully infuses the fish, there's little to prevent its spoilage - and depending on strength of the solution and size (thickness) of pieces of fish, if the process is fast enough, that's non-issue, but if it's to take 2-3 days in room temperatures, you may end up with pickled fish that's spoiled inside.