The Hermit and I enjoy pickled fish on crackers as a winter appetizer. Pickled herring is readily available at the grocery store, but we much prefer pickled northern pike which can cost $4-$5 for a tiny jar containing maybe ten tiny chunks of fish. Luckily, northern pike are abundant here in Minnesota and the process of pickling them isn't exactly rocket science. And I think home-pickled northerns taste much better.
I suppose a catchy name for this recipe would be "pickled pickerel", but around here we don't call members of the Esocid family "pickerel". They are northern pike, or just simply "northern". Before the days of heavy fishing pressure and big motors and fish finders, there would be a 20 pound lunker or two lurking in every lake. Nowadays it is more common to find abundant numbers of northerns that are mostly 3 pounds or less. A lot of people don't like to mess with these "hammer handles", even though you can get good fillets off them, because they have "Y" bones that are like the little plastic filaments that hold the tags to your new shirt. These bones can be removed by cutting the fillets a certain way, but if you pickle the fish the bones dissolve completely.
I work with a guy who has recently rediscovered the tradition of fish spearing. He really doesn't like eating fish, however, so recently he gave me fillets from two northerns he had speared. I didn't want to bother with cutting out the "Y" bones, so instead I pickled them. I had recently "practiced" on some store-bought northern fillets, with excellent results.
With any wild-caught fish, there is the possibility of tapeworm cysts in the flesh, so it's a good idea to freeze the fillets for 48 hours, which will kill any cysts. Then, the first step is to cut the fish into bite size chunks. Put the fish into containers and cover with a brine of 2 cups white vinegar, 1/2 cup pickling salt, and about 1/2 cup pickling spice. Recipes will vary on how long to keep the fish in the brine, but usually it works out to be 5-6 days when I do it. Shake the fish every so often to make sure the brine gets everywhere.
After the brine is drained, soak the fish in fresh water for about half an hour or more. While the fish are soaking, prepare a mixture of 4 cups white vinegar, 2 cups sugar, 3 T. pickling spice and 2 tsp. mustard seed. Bring to a boil and let cool. Caution: if you let it boil for a few minutes in an area that is not well ventilated, you won't be able to breathe in the kitchen. Ask me how I know.
Then, layer the fish in jars with slices of white onion, and cover with the sauce. I pour a little white wine in each jar if I have any, and add some whole peppercorns. Refrigerate for a week or so, and enjoy. The home economist food police say pickled fish should be consumed within one month, but I see no reason why it would not keep longer in the refrigerator. Freshness dates on commercial pickled fish are up to a year.