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How to Tell if Fish Is Bad

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A lot of people worry about whether the fish they buy at grocery stores is fresh or not. Here in the United States, we eat a lot less fish than in many other countries, so we’re not as used to handling and storing the meat.

As a result, it’s sometimes tricky to know when fish turns from fresh to rotten and how to store fish to keep it good for much longer.

One of the main challenges is that bad fish smells like fish! However, when a fish starts to sour, the smell becomes much more potent and morphs into an off-putting odor.

In addition, bad fish will begin to decay. It loses water in the meat and becomes mushy.

Sometimes, you’ll notice a slimy film around the surface of the fish that indicates it’s no longer good.

Cooking bad fish won’t make the smell or taste better. If you come across bad fish, you should throw it away because it can make you sick. It probably won’t taste terrific, either.

Here are some tips on how to tell if fish is bad and things you can do to best store your fish in the fridge or freezer.

fresh raw Dorado fish with lemon and herbs on kitchen table

Ways to Tell That Your Fish Is Bad

It’s hard to buy fish in a grocery store when you don’t know what you’re doing. Most people know their way around things like chicken breasts and ground beef. Buying fresh fish, however, is trickier.

Here are some ways to spot signs of bad fish to help you avoid any issues.

Check the Expiration Date

Almost every fish you buy at the grocery store will have both a sell-by and an expiration date on the packaging. The sell-by date is the cutoff for when the grocery store needs to sell the fish. The expiration date is how long you have to eat it.

When in doubt, you can always ask someone working in the meat section about how long you have to cook or freeze the fish. Buying something closer to the sell-by date will often get you a better deal, but you’ll have less time to cook it.

Never eat or buy fish past the expiration date because it can be bad and make you sick. Instead, throw it out and buy some new fish.

raw Salmon fillet steak in a pan

Slimy Coating

One of the best ways to tell if your fish is bad is by touching the skin or the fillet. A good piece of fish will feel cool to the touch. It will be moist but not wet. The meat should be relatively firm.

If you feel a slimy coating on your fish or you see that the texture is breaking down, you shouldn’t cook or eat that particular piece. The slimy film is a sign the fish is bad.

Additionally, excess water in the fish packaging is a worrying sign unless the fish is frozen and thawing. When the flesh starts to go bad, it leaks fluid and breaks down.

A Foul Smell

Of course, the way your fish smells is something you should always check whether you’re buying or preparing to cook it at home. One problem is that many people will tell you that a bad fish smells like fish, only stronger.

While this is true, it is hard to mistake the smell of a bad fish. Good fish have a fishy smell that’s lighter and more pleasant. Bad fish on the other hand, will smell like something that has been sitting on the beach roasting in the sun all day. If you can’t bear to smell your fish for long, then you may not want to eat it.

Raw Tuna steak on a plate

Changes in Color

Another way to tell whether your fish is fresh and ready to eat is if it still has its original color. Fish tend to change into blander colors the longer they are left out. So, pay attention to the color of whatever fish you buy. When you cook it, it should resemble how it looked when you purchased it.

Freezer Burn

Freezing fish certainly keeps it in good shape for much longer, but one issue with fish is that it’s relatively easy to get freezer burn.

Sometimes the fish you buy in the store has thawed and been refrozen. This isn’t always a problem, but freezer burn can affect how the fish tastes.

Look at the edges of the fish cutlets and see if you can spot any crystalized ice around the corners. This could be a sign it’s freezer-burned, so you may want to buy a different package or type of fish.

These are some of the best ways to tell if a fish is bad. Generally, you should hesitate to buy it anytime you think there’s something wrong with the fish.

Of course, you can always ask someone in the store who works in the meat section what they think. They should guide you to a fresh fish that will last until you decide to cook it.

Sashimi (japanese food). Sliced raw seafood in a bowl

Cooked Fish vs. Raw Fish

Only certain grades of raw fish are suitable for eating. Don’t eat any fish unless it’s either marked as sashimi or you’re familiar enough with the meat to know what you’re doing.

Is slimy fish OK to eat? Again, anytime you feel slime on your fish, you certainly don’t want to eat it raw, and you should inspect it closely before you cook it.

How to Know if Cooked Fish Is Bad

We’ve spent a lot of time on raw fish, but how do you know if cooked fish is still good?

The same rules apply, only you’re focused on how your fish steak or fish fingers smell, feel, and taste compared to fish you’ve had in the past. Never eat any fish that tastes “off” or smells bad. Also, throw it in the trash if it’s mushy or if there’s obvious mold growing on the meat.

Freshly cooked Buttered Tuna fish

Storing Fish

Knowing how to store fish properly will help you keep it in good condition for longer. Let’s look at different ways to store fish and how long it should last.

How long does raw fish last in the fridge? Raw fish should typically be in the fridge for a few days. You should freeze it first if you’re not going to cook it soon.

Cooked fish, on the other hand, will last longer in the fridge. You can expect it to last up to a week.

What about the freezer? How long does raw fish last in the freezer? Fish can last in the freezer for years if you have a cold enough freezer and a steady power supply.

You can freeze cooked fish too, but it won’t taste the same once you thaw it. So, it’s probably best to only freeze raw fish.


Knowing when a fish is already bad can be the deciding factor between eating healthy and ending up in the hospital for food poisoning. This is why the tips given above are important to help you identify bad fish from some that is fresh and fit for consumption. Whatever you do, never eat fish that you feel is bad; it is not worth the risk.