I just finished pickling some Northern. They are better than pickled herring.
Freeze fish for 3 weeks to kill any parasites.
Chunk fish
Mix 4 cups water and 1 cup canning salt
Cover in refrigerator for 48 hours
Drain and wash
Cover with vinegar in refrigerator for 24 hours
Drain and pack in jars with onions
Boil and let cool:
2 cups vinegar
2 cups sugar
2t mustard seed
1t whole allspice
1t whole cloves
1t red pepper flakes
4 bay leaves
When cool add 1/2 cup white wine
Pour over fish and onions in jars and store in refrigerator for 3 weeks before eating
A 4lb northern and 2 medium onions will pack 4 pint jars with enough brine to cover them. If you do more you need to make more brine. There is no canning process so the pickled fish must always be kept in the refrigerator. The y bones will be dissolved in the brine.