At 0 degrees Fahrenheit or below, frozen fish stays safe indefinitely. However, after a period of time, the quality of the fish decreases. Look for telltale signs on the surface of the fish to determine if you can use it. Depending on your recipe, the fish may work fine with a few modifications, or it may need to be tossed in the trash.
Typical Storage Life
Different varieties of fish remain good in the freezer for different lengths of time. For example, salmon retains its quality for two to three months, while cod stays good for six to eight months. Either use the fish in your freezer before expiration or plan on using the fish in a way where soft or mushy texture doesn't matter, such as in a fish pate to serve with crackers or vegetables.
Signs of Spoilage
The signs of bad frozen fish depends on whether it's frozen or thawed. In frozen fish, look for:
- Whitish or grayish-brown dry, flakes or patches, called freezer burn, at the edges of the fish or over the surface, indications that they fish has dried out. Cut away the dry portions of the fish.
- Lighter weight than the fish had when you put it into the freezer, a sign that moisture in the fish has evaporated. You can still cook the fish, but it might be more tough than tender.
After you've thawed the fish, look for these signs, and throw the fish away if you see them:
- A slimy film over the surface of the fish, indicating the presence of bacteria.
- An off-odor of ammonia or fishiness.
Frozen fish can go bad if your freezer stops working during a power outage. If you suspect that the fish has thawed and refrozen, throw it away to be on the safe side -- bacteria grow rapidly within two hours at temperatures even a little above 40 degrees F, according to the U.S. Food Safety and Inspection Service.
Thawing Frozen Fish
If your fish filet is thin enough, you can cook it directly from the freezer. After it's thawed, cook the fish immediately or place it in the refrigerator. You have a few options to thaw fish safely:
- Defrost the fish overnight in the refrigerator. Place it in a bowl or on a plate to catch drips.
- Place the fish in an airtight bag and immerse it in cold water. If the fish takes more than 30 minutes to thaw, change the water to help ensure that it stays cold.
- Microwave the fish in 1-minute intervals until thaws; a few lingering ice crystals are fine.
When thawing frozen fish, never thaw it at room temperature on the kitchen counter. The amount of bacteria on foods at room temperature can double within 20 minutes, according to the Foodsafety.gov website.