How to Tell if Fish Has Gone Bad

12 November, 2018
Eating bad fish can cause food poisoning, so it's important to take extreme precaution when assessing the freshness of your fish

Fish is one of our most important foods, thanks to its high nutritional value and for being easy to digest. There are many ways these days to conserve and transport it with the goal of keeping it fresher for longer. However, sometimes these methods don’t work out. For that reason, you need to know how to tell if fish has gone bad.

Most people want convenience when buying it, and they want it filleted and decapitated. It’s easier to eat these fish without knowing if they’re fresh or not, because you normally buy them already frozen.

How to tell if fish has gone bad

Identify Bad Fish

  • Smell: Your fish has gone bad if it has a rancid smell; it can occasionally smell like ammonia.
  • Skin: It will have very soft skin that easily detaches from its scales and meat.
  • Eyes: It’ll have sunken eyes, creamy corneas, and gray pupils, as if it has cataracts.
  • Gills: Their gills are behind their head, and are yellowed or gray.
  • Guts: This is the first area affected by aging; you will find the fish to be swollen or flaccid and sunken.

Want to learn more?6 Types of Risky Fish that You Should Never Eat

In good condition?

Fish with assorted vegetables

Smell: Fresh fish smells like seaweed, the sea, and conserves all of its nutrients.

Skin: If it’s fresh it’ll have a vibrant color, with hard and shining scales.

Eyes: It’ll have protruding eyes, with black pupils that glisten.

Gills: The gills will be pink or red, depending on the species, clean, bright, and without mucous.

Guts: The meat is firm and not slippery.

Tips to prevent unwanted surprises

Cut half of fish

So that you don’t have to throw it away, we recommend that you cook it within a few days of buying it from the supermarket. If this isn’t possible, you can freeze it. This guarantees its that it will stay fresh for longer. By freezing it, it conserves its properties and prevents the risk of food poisoning.

Something important to note is that eating fish that has been in the freezer if you haven’t been at home for a few weeks can be quite risky. This is because you don’t know if there were power failures, which would mean that it wasn’t properly frozen.

Generally speaking, frozen products shouldn’t be out of the freezer for longer than 2 days after they have been frozen. Freezing them again is never recommended. If you discover defrosted fish due to power failure, the safest option is to throw it away.

Refrigeration and freezing prevent the proliferation of more bacteria, but it doesn’t kill them. This allows the decomposing process to accelerate.

Check out this article: 5 Virtues of Fish Oil for Your Health

The moisture content

Assorted fish in ice

When you cook fish, you should look to see whether there is a lot of frozen liquid around it or if it’s dry. If there is liquid present in the bag or container, this means that there could have been some kind of power failure that caused it to defrost.

If everything seems to be OK, you still have to be careful. Defrost it, look at it and smell it. If it has a normal smell and appearance, it’s safe to eat. If not, it’s probably not a good idea. It shouldn’t be eaten the same day if it was caught in salt water. Dry it well and first put it in the refrigerator. Finally, you’ll know if it’s fresh or not once you take that first bite.

If it doesn’t taste sour or acidic then it’s OK. Your taste buds will know if something isn’t right. If all is in order, you can go ahead and eat it!

  • Evaluación de la calidad del pescado. (s.f.). En Organización de las Naciones Unidas para la Alimentación y la Agricultura (FAO). Recuperado el 16 de diciembre de 2017 de
  • Enfriamiento o congelación del pescado. (s.f.). En Organización de las Naciones Unidas para la Alimentación y la Agricultura (FAO). Recuperado el 16 de diciembre de 2017 de