Fish for freezing should be as fresh as possible.
Preparation — Wash fish, and remove scales by scraping fish gently from tail to head with the dull edge of a knife or spoon.
Remove entrails after cutting entire length of belly from vent to head. Remove head by cutting above collarbone. Break backbone over edge of cutting board or table.
Remove dorsal or large back fin by cutting flesh along each side and pulling fin out. Do not trim fins with shears or a knife because bones will be left at the base of the fin.
Wash fish thoroughly in cold running water. Fish is now dressed or pan dressed, depending on size. Large fish should be cut into steaks or fillets for easier cooking. For steaks, cut fish crosswise into ¾-inch thick steaks. For fillets, cut down back of fish from tail to head. Then cut down to backbone just above collarbone. Turn knife flat and cut flesh along backbone to tail, allowing knife to run over rib bones. Lift off entire side of fish in one piece, freeing fillet at tail. Turn fish over and cut fillet from other side.
Pretreating — Fish are categorized as either fat or lean fish, by the amount of fat in their flesh. “Fat fish” includes varieties such as mullet, mackerel, trout, tuna and salmon. “Lean fish” includes flounder, cod, whiting, redfish, croaker, snapper, grouper, sheepshead and most freshwater fish.
Before freezing, fish can be pretreated to improve the quality of the stored fish. Fat fish should be dipped for 20 seconds in an ascorbic acid solution made from 2 tablespoons crystalline ascorbic acid to one quart of cold water to control rancidity and flavor change. Lean fish may be dipped for 20 seconds in a brine of ¼ cup salt to 1 quart of cold water to firm the fish and to decrease drip loss from thawing. (These pretreatments are not needed if a lemongelatin glaze is used.)
Packaging — Fish may be frozen using any of the following methods. If several fish are placed in the same package, place freezer paper or wrap between them for easier separation.
This document was extracted from "So Easy to Preserve", 5th ed. 2006. Bulletin 989, Cooperative Extension Service, The University of Georgia, Athens. Revised by Elizabeth L. Andress. Ph.D. and Judy A. Harrison, Ph.D., Extension Foods Specialists.