Preserving fish safely

Handling your catch of the day begins with cleaning, and icing or freezing the fish as soon as possible. The four most popular methods of fish preservation are freezing, canning, smoking and pickling.

Top quality fresh fish are essential for fish preservation. Of all flesh foods, fish is the most susceptible to tissue decomposition, development of rancidity and microbial spoilage. Safe handling of fish is important to reduce your risk of foodborne illness and to produce a quality meal.

How to prevent spoilage in freshly caught fish

Keep freshly caught fish alive as long as possible

Monitored live wells or mesh baskets kept underwater keep fish alive longer than a stringer. Spoilage and slime-producing bacteria are present on every fish and multiply rapidly on a dead fish held in warm surface water. Fish begin to deteriorate as soon as they leave the water.

Clean the fish as soon as possible

Thorough cleaning of the body cavity and chilling of the fish will prevent spoilage. Fish spoilage occurs rapidly at summer temperatures; spoilage is slowed down as freezing temperatures are approached.

Put the fish on ice

Ice is the key to fresh tasting fish. Pack cleaned fish in a cooler of one pound of crushed ice for each two pounds of fish. Fish held at refrigeration temperatures of 40 degrees F or lower may have a shelf life up to three days depending on refrigerator temperature and original fish quality.

Preserve your catch

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This is the simplest, most convenient and most highly recommended method of fish preservation. A good quality frozen product requires the following:

• Careful handling of the fish after catching.
• Removal of the guts and thorough cleaning of the fish soon after catching.
• Wrapping material or method that is airtight and prevents freezer burn and the development of undesirable flavors.
• A freezer storage temperature of 0 degrees F or lower.

To freeze fish

Remove the guts and thoroughly clean the fish soon after catching.

Option 1

1. Prepare the fish as you would for table use. Cut large fish into steaks or fillets. Freeze small fish whole.
2. Wrap the fish in heavy-duty freezer bags. Separate layers of fish with two thicknesses of packaging material for easier thawing.
3. Label the package with the type of fish, number of fish or fillets and the date.
4. Store in the freezer at 0 F or lower.

Option 2

1. Small fish, such as sunfish and panfish, or small servings of fish can be frozen in ice.
2. Place the fish in a shallow pan or water-tight container.
3. Cover with ice water and place in the freezer until frozen (8-12 hours).
4. Remove block from container and wrap.
5. Label the package with the type of fish, number of fish or fillets and the date.
6. Store in the freezer at 0 F or lower.

To thaw fish

The safest way to thaw fish is in the refrigerator for 12 to 24 hours. Fish can be thawed in the microwave on defrost, allowing 5 to 7 minutes for 1 pound of frozen fillets, depending on microwave power and amount of fish. Plan to cook immediately after thawing. Do not thaw fish at room temperature.

Thawing vacuum packaged fish has specific considerations for safe thawing. While vacuum packaged fish shelf life can be extended from 6 months to a year or more and results in a tasty and superior fish. For food safety, it is critical to follow these thawing instructions for all home frozen or store-bought vacuum packaged fish:

• Prior to thawing in the refrigerator or immediately after thawing, remove the fish from the package. By opening the package when thawing, oxygen is present and prevents germination of C. bot toxins associated with botulism. 
• Follow safe thawing directions on commercially vacuum packaged fish.

Never refreeze fish.

Cut large fish into steaks or fillets.

Storage life of good quality frozen fish held at 0 F or lower

(Source: Minnesota Sea Grant, 2012)

• Northern pike, trout, whitefish, smelt, lake herring, carp: 4 to 6 months.
• Chinook salmon, coho salmon, white bass: 5 to 8 months.
• Walleye, bass, crappie, sunfish, yellow perch, blue gill: 8 to 12 months.

Fish is a low acid food and can be processed safely only at temperatures reached in a pressure canner. Failure to heat process fish at 240 degrees F or higher may allow spores of the dangerous heat-resistant bacteria, Clostridium botulinum, to survive, germinate, and grow. The poison produced by botulinum bacteria causes botulism, a deadly food poisoning. The addition of small amounts of vinegar, or packing fish in tomato juice or tomato paste, does not remove the requirement for heat processing fish in a pressure canner.

Use standard heat-tempered canning jars. All processing times listed are for 1-pint jars. Wide-mouth pint jars will be easier to fill than narrower ones.

General USDA method for canning fish without sauce

** This includes blue, mackerel, salmon, steelhead, trout and other fatty fish except tuna.

Clean and gut fish within two hours after catching. Keep cleaned fish on ice until ready to can.

Note: Glass-like crystals of magnesium ammonium phosphate sometimes form in canned salmon. There is no way for the home canner to prevent these crystals from forming, but they usually dissolve when heated and are safe to eat.

Procedure

1. Remove head, tail, fins and scales.
2. Wash and remove all blood.
3. Split fish lengthwise, if desired.
4. Cut cleaned fish into 3 ½ inch lengths.
5. Fill pint jars, skin side next to glass, leaving 1-inch headspace.
6. Do not add liquids.
7. Adjust lids and process.

Processing procedures for Minnesota altitudes

1. Dial-gauge pressure canner.
   Pints - 100 minutes 11 PSI.

2. Weighted-gauge pressure canner.
   Pints - 100 minutes 15 PSI.

Heat fish to boiling temperatures for 10 minutes before tasting or serving. For canning fish in quart jars see Canning Fish in Quart Jars from University of Alaska Cooperative Extension.

Pickling is an easy method of preserving fish. Pickled fish must be stored in the refrigerator at no higher than 40 degrees F (refrigerator temperature) and for best flavor must be used within 4 to 6 weeks. Only a few species of fish are preserved commercially by pickling but almost any type of fish may be pickled at home.

The first step in producing safe, home-pickled fish is to kill the larvae of the broad fish tapeworm, a parasite that can infect humans. It's most common in northern pike, but is found in several Minnesota fish. See the section below for methods to destroy the tapeworm larvae.

Refrigerate the fish during all stages of the pickling process.

Ingredients for Pickled Fish

• Fish - Use only fresh, high quality fish.
• Water - Avoid hard water, as it causes off color and flavors.
• Vinegar - Use distilled, white vinegar with an acetic acid content of at least 5 percent (50 grains means the same thing). This percentage of acetic acid is needed to stop bacterial growth.
• Salt - Use high grade, pure canning or pickling salt. It does not contain calcium or magnesium compounds which may cause off color and flavors in pickled fish.
• Spices - Fresh, whole spices.

General method for precooked pickled fish

1. Soak fish in a weak brine (1 cup salt to 1 gallon of water) for 1 hour.
2. Drain the fish.
3. Pack in heavy glass, crock, enamel or plastic container in strong brine (2 ½ cups salt to 1 gallon of water) for 12 hours in refrigerator.
4. Rinse the fish in cold water. Cut into serving-size pieces.
5. Combine the following ingredients in a large pan or kettle. This makes enough for 10 pounds of fish.
   • ¼ ounce bay leaves
   • 2 tablespoons allspice
   • 2 tablespoons mustard seed
   • 1 tablespoon whole cloves
   • 1 tablespoon pepper, ground
   • 1-2 tablespoons hot, ground dried pepper
   • ½ pound onions, sliced
   • 2 quarts distilled vinegar (5% acidity)
   • 5 cups water (avoid hard water of high mineral content)
6. Bring to a boil.
7. Add fish and simmer for 10 minutes until fish is easily pierced with a fork. Don't overcook.
8. Remove fish from liquid and place on a single layer on a flat pan.
9. Refrigerate and cool quickly to prevent spoilage.
10. Pack cold fish in clean glass jars adding a few whole spices; a bay leaf, freshly sliced onions and a slice of lemon.
11. Strain the vinegar solution, bring to a boil and pour into jars until fish is covered.
12. Seal the jar immediately with two-part sealing lid, following the manufacturer's instructions.
13. Pickled fish must be stored in the refrigerator as stated in general directions.

The broad fish tapeworm infection can be contracted by humans from eating raw or undercooked species of fish found in the Great Lakes area. 

There are two schools of thought on how to destroy the tapeworm. With the first, simmer fish in pickling brine to 140 degrees F. This does not affect the flavor or the texture of pickled fish. Or, if you are pickling raw fish, freeze it at 0 F for 48 hours prior to brining. Either method kills the parasite.

Those who wish to prepare raw pickled fish should first freeze the fish at 0 F for 48 hours.

The larvae of the broad fish tapeworm pass through smaller fish until they lodge as hatched small worms in the flesh of large carnivorous species of fish, like northern pike, walleye pike, sand pike, burbot, and yellow perch. This worm, if eaten by humans in its infective stage, can attach to the small intestine and grow to lengths of 10 to 30 feet.

The infective worms are destroyed readily either by cooking or freezing. Two recent outbreaks of this tapeworm in Minnesota were related to eating uncooked pickled pike.

Smoking has long been used as a means of temporarily preserving fish. The steps in the smoking process are necessary not only for safe preservation, but also to produce good flavor and aroma. Carp, suckers, buffalo catfish, salmon, trout and chubs may be successfully smoked. A safe, high quality product can be produced using the following brining and smoking procedures.

Certain steps in the brining and smoking process require careful attention.

Brining

• Use correct amount of salt in the brine.
• Use enough brine for a given amount of fish.
• The temperature during brining must be no higher than 40 degrees F.
• Use similar size and kinds of fish in the brine.

Smoking

• There should be uniform heat treatment of all fish in the smoking chamber.
• Use freshly caught, dressed fish, whole or filleted.
• Wash fish thoroughly.

Steps for safe smoked fish

• Use freshly caught, dressed fish, whole or filleted.
• Wash fish thoroughly.
• Fish for smoking must be brined.
• 1 ½ cups salt to 1 gallon water – 12 hours in refrigerator.
• 4 cups salt to 1 gallon cold water – 15 minutes.
• Remove from brine, rinse.
• Place short stem of meat thermometer in thickest portion of flesh of largest fish.
• Put fish in smoker when air temperature is 100 F. (You need a second thermometer to measure this.)
• During smoking, air temperature should rise to 225 F.
• Fish flesh should reach 180 F and be kept there for 30 minutes.
• Fish smoked must be stored in refrigerator. Use within one month.
• Canning smoked fish procedure from the National Center for Home Food Preservation.

Deb Botzek-Linn, William Schafer and Suzanne Driessen, Extension educator

Reviewed in 2021