How to Tell if Fish is Bad?

How to Tell if Fish is Bad? Fish is a staple food that almost everyone has eaten at one point in their life. If properly prepared, it can be made into an exquisite delicacy; a treat for your taste buds. However, that is only if you cook and eat fresh or properly frozen fish.

Consuming a bad fish can have disastrous consequences to your health as it might result in food poisoning which is an illness caused by harmful microorganisms present in spoiled food. Luckily, there are quick and easy ways to determine if fish has gone bad or if it is still edible.

How do you ensure that your packaged fish is safe to eat? There are many ways to determine if a fish is bad or rotten. The first one I would mention is the sell-by and use-by date.

What do a Sell-by and Use-by date mean?

Have you ever wondered what the sell-by date on the packaged fish you purchased mean? This date marks the recommended time a perishable product (in this case fish) is meant to be sold.

Stores are expected to remove this product from their stalls after this date has passed because it signals that the fish will start to lose its optimal product quality. If the fish has a use-by date instead, it means the fish will begin to spoil if not eaten before or on the date.

What does this mean to consumers? For one, it signifies that the fish purchased is of impeccable quality and that it is safe for consumption.

However, it is important to note that raw fish can only last one or two days in a refrigerator after its sell-by date. If a couple of days has passed, you should discard the fish because it is no longer safe for consumption.

A way to extend the quality of your purchased fish is to cook it immediately and keep it sealed in a container in the refrigerator. Nonetheless, it can only stay good for less than a week if you use this method.

How can you tell if fish is spoiled?

How can you tell if fish is spoiled?

It is difficult to accurately determine the expiration date of perishable products therefore you will have to use your sensory organs to inspect if your fish has gone bad.

The signs to look out for

The first and most obvious way to determine if a fish has gone bad is its smell. If you notice a foul smell coming from your fish, it is a very good sign that it is not safe for consumption. Raw fish, cooked fish, and refrigerated fish will start to give off a putrid stench when they go bad.

Second, you can check for a slippery coat on the outer surface of the fish. Raw fish will set about developing a thick and slimy coating on its surface when it starts to go bad. You can run your hand along its scales to check for this. This type of inspection only works on raw fish.

Another factor to pay attention to is the color of the fish. If there is a color change different from the original color of the raw fish, you should suspect that the fish might have gone bad and it will be injurious to your health if consumed.

Finally, this last tip is specific to salmon. If you notice the color of the wavy white lines present on your salmon has turned grey, it suggests that it has gone bad and it will be dangerous to consume.

Health concerns related to eating bad fish

Food poisoning from fish can cause painful and sometimes serious health concerns. The two types of poisoning one can get from eating bad fish are ciguatera poisoning and scombroid poisoning.

Both of these types of poisoning are hazardous to health therefore it is essential that you are knowledgeable about its symptoms and how to prevent them. Whenever you notice symptoms relating to food poisoning, it is important that you seek medical care immediately.

Scombroid Poisoning

This is caused by eating fish that has not been properly preserved or that has passed its use-by date. Basically, there is a high chance to get scombroid poisoning if you consume a bad fish. Symptoms related to this poisoning are headache, itching, nausea, abdominal pain, and diarrhea.

They usually happen after a few minutes of eating the contaminated fish. This poisoning is mild because it is possible to get better within one to two days without clinical treatment.

Ciguatera Poisoning

This is caused by ingesting fish adulterated by the toxins produced by algae around coral reefs. This is a more serious case of food poisoning as it can last for as long as a few days to months or even years. Its symptoms vary but may include nausea, vomiting, diarrhea, and stomach pain, which is quite similar to the symptoms of scombroid poisoning.

This poisoning can be fatal because a poisoned person may later develop life-threatening complications such as difficulties in breathing, bradycardia (abnormally slow heart rate), or coma.

There is no known cure for this toxin and doctors can only provide care that will alleviate the symptoms. However, it is important to note that ciguatera poisoning is a very rare occurrence.

Preservation Methods and fish shelf life

Certain fish go bad earlier than other fish. If you are passionate about seafood, it is necessary to know how long different fish lasts before they get spoiled.

Fish generally lasts in a refrigerator for 1 to 2 days while they can be stored for months in a freezer. The factor that determines how long a fish might last in a freezer is its fat content. Generally, according to fat content, there are two major categories of fish.

We have the lean fish and the fatty fish. When it comes to freezing, the respective time in which their quality is maintained is discussed below:

Lean fish like cod, tilapia, flounder, pike, bass and pollock, are low in fat. Generally, they tend to last more while frozen, unlike fatty fish. They can stay frozen without losing out on quality for as long as 6 months.

Fatty fish like salmon and tuna have a shorter freezing time than lean fish. Salmon is a good source of protein, potassium, vitamin B12, and vitamin D. Tuna is a great source of iron, potassium, and vitamin B6. They both make a good meal that is delicious as well as nutritious.

Salmon and tuna can be stored in a refrigerator for at most two days before it starts to go bad. If it is not consumed within those two days, you can keep it in a freezer. A freezer will maintain the fish’s freshness for three months. Any longer than that and you will have an edible but low-quality fish on your hands.

A handy tip to always remember when freezing fish is to always make sure to add a label on the fish container which will indicate the time the fish was put in the freezer.

Vacuum sealed freezing

This is a freezing method that guarantees the long-term preservation of your fish. Vacuum sealing is a method of packaging that removes air from the container holding your fish thereby preventing moisture from evaporating from your food.

It also preserves and keeps fish at the optimal quality over a significantly extended period of time. Both lean and fatty fish can last up to two years using this preservation method.

Vacuum sealed freezing also saves money as you can purchase your seafood in bulk which will come at a reduced price. If you plan to save money and quality by buying in bulk, vacuum-sealed freezing is the way to go.

Frequently Asked Questions on How to tell if fish is bad

How to tell if fish is bad

What happens if you eat fish that has gone bad?

Eating bad fish is dangerous to your health. If ingested, harmful bacteria in it might cause you to have food poisoning and the level of severity will depend on how much of the contaminated fish is eaten.

Is it OK to eat fish that smells fishy?

To answer this, we would need to determine if the question is referring to saltwater fish or freshwater fish. Saltwater fish tend to have a strong “fishy” smell. This smell starts immediately after fish is killed because bacteria break down the trimethylamine oxide present in saltwater fish to trimethylamine which gives the popular “fishy” smell.

This odor can be removed by simply washing the fish with tap water and treating it with lemon, vinegar, or any other acidic ingredient. Also, another tip that can help to remove this “fishy” odor is by soaking the fish in milk for some minutes.

On the other hand, freshwater fish do not generally have this strong fishy smell with the exception of the catfish and its “fishy” smell can be removed just like how you would remove that of a saltwater fish.

If a fresh fish smells fishy it is normal but if you have had it for a few days and the “fishy” smell gets pungent, it is a good idea to throw that fish away.

How long before fish goes bad?

A raw fish left unrefrigerated would retain its quality for just two hours. Therefore, it is important to quickly refrigerate or freeze fish if you intend to preserve its freshness.

How long does fish last in the fridge?

Fresh fish will last for 2 to 3 days in a refrigerator, that is, it will retain its optimal quality for this period of time.


Fish is a good source of protein as well as other essential vitamins but it doesn’t last for long with conventional preservation methods. If you keep it raw in a refrigerator for more than two days, it will start to go bad.

Also, harmful microorganisms will start to grow in it and these organisms can be injurious to human health. Hence, it is important to know how to preserve it if you don’t intend to eat it soon.

Leave a Comment