Plug cut them -----left spin for upriver, right spin for downriver trolling. :p
Seriously, do cut, then do the rock salt, water, and powdered milk (1 C per qt) add some herring scent.
They will be firm, bright, and smell good.......
I have some in my 'beer' fridge, 9 months old, still look good ------probably some Norskys out there who would love to eat them for lunch.