Telling when fish is fresh and when it isn’t doesn’t have to feel like muddy waters. Here are the signs to look for.

Fish is one of the most delicious delicacies of world cuisine. It has a fantastic variety and can be used in a variety of recipes to create mouthwatering main courses and delectable side dishes.

Although fish is so popular, the logistics around it often scare budding chefs: Bough, cooked, and stored properly, fish is tasty and nutritious at any time of day. Bought, prepared, and stored poorly, fish can taste bad and, in extreme cases, make you sick.

Fear not; you are at Home Cook World. As always, we’ve got you covered. We have put together the best ways to tell if the fish in your fridge, raw or cooked, has gone bad. By the time you are done reading this article, you might as well consider a change of profession to fishmonger!

How to Tell If Your Fish Is Fresh

Fish, whether whole or filleted, is one of those foods that should be bought, cooked, and served as fresh as possible. If you enjoy preparing and eating fish, knowing how to tell if a fish is fresh or not is a must-have skill.

Happily, all it takes to develop that skill is a bit of knowledge and some good ol’ practice. We will go into the details of it in a moment. For now, here is all you need to know:

The best way to tell if a fish is fresh is to use your sight, smell, and touch. A fresh fish has clear and slightly bulging eyes, bright and shiny skin, and smell like the sea (or have no smell at all).

We recommend that you buy your fish at a local fish market, from the fishmonger, or the grocery store fish counter. Generally, at any retailer where you can look at the fish, touch or hold it, and give it a good whiff.

If you buy your fish at a market with multiple fresh seafood vendors, you can compare prices and quality more easily. If there is only one vendor at the market, or you are at a fishmonger or grocery store, your options are limited to their selection—and their selection only.

Online retailers are convenient, we know. But when you shop from them, you leave the selection to the staff, so the freshness of the fish can vary between individual purchases. Of course, that shouldn’t discourage you from buying from a retailer whom you trust.

How to Select Fish at the Fish Market

How to tell if your fish is fresh
How to tell if your fish is fresh

To select fish at the market, once again you will want to use your senses of sight, touch, and smell. You are basically looking for fish that looks as if it jumped right out of the water.

Touch the fish or hold it in your hands:

The fish itself should feel firm; its skin elastic. Despite lore to the contrary, some slime on the surface is fine as long as that slime is glossy, translucent, and does not smell foul.

Take a close look at the eyes, scales, and gills of the fish:

You’re looking for lively, bulging, dark black eyes (not dead, gray, sunken eyes). The scales should be shiny and attached to the body firmly.

Dry, detached scales are a sign that the fish is dated, and thus past its prime. The gills should be red, telling you that the fish was just gutted, and not brown, a sign of rotting.

As Amelia Simmons puts it in the 1796 book American Cookery, the first known cookbook written by an American: “In all great fish-markets, great fishmongers strictly examine the gills—if the bright redness is exchanged for a low brown, they are stale.”

Smell the fish:

Some fish, when still fresh, smell like the sea or the ocean; others smell a little like mud; then there’s fish that does not smell at all. Whatever the case, one thing is certain: a strong smell is a sign that the fish is old.

Salmon, mackerel, herring, and anchovies are naturally fatty. Bass, cod, flounder, and red snapper tend to be on the leaner and, for the same reasons, flakier side. No matter the type of fish you’re shopping for, the fat should never smell sour or rancid.

Choosing packaged fish at the grocery store:

If you do not live near the sea and there is no fish market nearby, you should adjust your expectations about the freshness of the fish you can get. If the fish comes from far away and is not frozen, travel and display have taken their toll.

Let’s say you are at the store and can not smell or touch the fish. The appearance of the fish and the best-before/sell-by date on the package are the two most obvious clues, especially if you are buying it at a reduced price. The fish should look glossy and moist; dullness and dryness are signs that it is dated.

How to Tell If Raw Fish Has Gone Bad

We have established how to select fresh fish. So let’s say that you did exactly that, but you left the fish on the counter or in the refrigerator a little too long than you should have.

How do you know if raw fish has gone bad?

Tell-tale signs that raw fish is spoiled are that it is sticky and slimy to the touch; the fish has sunken eyes, detached scales, and dark brown gills; and/or it smells appallingly of fish.

Fish, raw or cooked, shouldn’t be left to sit out at room temperature for longer than 2 hours, or bacteria may grow to dangerous levels inside it and give you food poisoning. On a sultry summer day, that time is shortened to 1 hour.

This has important implications for how you buy fish. If you live far from town and have to make shopping trips to buy food, always buy your fish last so it doesn’t sit in your car’s trunk (or your truck’s bed) for too long.

If you suspect your fish is bad, play it safe and throw it away (ideally, wrapped in paper or plastic so that wild animals would have a hard time grabbing it from the trash can and getting sick from eating it).

How to Tell If Cooked Fish Has Gone Bad

Leftover fish should be stored in the fridge within 1-2 hours after cooking, where it will keep for 3-4 days. Wrap the fish in plastic or aluminum foil or, even better, store it in a food storage container with the lid shut.

Cooked fish is spoiled when it is sticky and slimy on the surface, and its texture has changed from firm and fall-apart flaky to soft and weirdly mushy. This typically happens within a few days of refrigeration.

Throw away all fish leftovers if you suspect that they may have spoiled. Spoiled fish isn’t edible—it can irritate your stomach and give you a bad case of food poisoning—and reheating it (or cooking it twice) won’t make it any safer.

According to the U.S. Centers for Disease Control and Prevention, 48 million Americans per year get sick from food poisoning. Of them, 128,000 are hospitalized and an unfortunate 3,000 die. In other words, it is simply not worth it to gamble with your well-being by eating spoiled fish.