Here you go Mac.
First, use only fully frozen fillets. Eliminates the risk of any parasites.
Brine:
Dissolve enough kosher or pickling salt in cold water to float a raw egg (in the shell)
Brine overnight or at least 8 hours.
Rinse fillets with clean water a couple of times and set aside.
Pickle:
2c white vinegar
1c cider vinegar
1c white wine (I prefer Pinot Grigio)
1c sugar
2tbsp pickling spices
Bring mixture to a boil to dissolve the sugar and infuse the spices.
Strain the spices and cool
Layer sliced white onions and fish in a jar
Cover with pickle
Remove air bubbles with a chopstick
Refrigerate for a week ( if you can stand it that long.)
I’ve done perch, gills, walleye, crappie and pike with this recipe. Don’t have a clue how it’ll work with salt water fish.