Fish caught on a fishing trip are good for freezing for later use if they are brought home in good condition. Proper preservation begins the moment the fish is hooked and pulled from the water. How you initially handle a fish can greatly affect its quality, taste and storage life.
First of all, the fish should not be allowed to flop around on the ground or in the bottom of a boat, where repeated bumping against raised ribbing and other objects can cause bruising and result in defects in the frozen product.
Once the fish has been restrained and the hook removed, it is best to keep it alive as long as possible. Most modern sport fishing boats are equipped with a live well designed specifically for this purpose. If a fish is too large for the live well or a live well is not available, the next best method is to use a stringer or a fish basket hung over the side of the boat, or put it in a container of clean water.
If a fish dies, it should be gutted and cleaned as soon as possible. In the meantime, remove the dead fish from the water so its flesh doesn't absorb water and swell. If a cooler of ice is not immediately available, wrap the fish loosely in damp cloth or paper and place it in a shaded area, out of direct sunlight (under a boat seat, for example). Leave space around the wrapped fish for air to circulate and evaporate the moisture from the wrapping material, which will help keep it cool.
Keep the wrapping material moist so the wrapped fish stays cool and its skin does not become dry.
Pack your catch in a cooler with plenty of ice before transporting it home. The cooler or ice chest should have a raised false bottom to collect the water from the melting ice. This will keep the fish from floating in and possibly soaking up water in the bottom of the chest. If the trip home is a long one, you should occasionally stop and drain the ice-melt from the chest. Once you are home, the fish should be processed and frozen as soon as possible.
Failure to promptly ice your catch may result in the flesh having a soft, open texture. Severe deterioration is indicated by a condition called "belly burn" in which the ribs have become separated from the flesh. Inadequate bleeding and delayed gutting will cause blood clots to form in the flesh. Such fish are not suitable for freezing.
Cleaning Your Catch
You need a sharp knife and plenty of clean water. Wash the fish to remove all surface dirt and excess slime. Start by opening the fish's body cavity by cutting along the belly from the vent (anus) to gill collar, taking care not to puncture any internal organs.
Next, cut the gills loose from the backbone at the base of the head, and cut them free from the belly next to the pectoral (lower front) fins. Complete removal of the gills will lengthen its frozen storage life. Detach the lower intestine by cutting around the vent or simply trimming it free.
Holding the fish by its gills, pull the internal organs and other viscera from the body cavity. Lastly, cut the kidney membrane along the backbone and remove the blood by scraping it with your thumbnail or a teaspoon.
Further cleaning of the fish will be determined by the form in which it is to be preserved. The fish may be frozen in this form, or you may wish to skin and/or fillet the fish beforehand.