In a large nonreactive soup pot, add the salt to 1 gallon of water. Stir well and allow to sit until the salt dissolves, stirring occasionally.

Rinse the fish fillets in cold water. Add the fillets to the salt brine and set aside for 45 minutes.

In a nonreactive medium saucepan, combine vinegar, sugar, and pickling spices. Bring to a boil over high heat, stirring until the sugar dissolves. Remove from the heat and set aside to cool completely.

When the pickling mixture is cool, add the red and green peppers, white and red onions, and the dill. Drain the herring completely and add to the mixture. Cover and refrigerate for 3 to 4 days, gently stirring occasionally.

Pack the herrings and vegetables in sterilized jars and fill with the pickling liquid. Cover and refrigerate. (Marinated fish will keep up to 3 weeks.)