Is seafood supposed to smell fishy?

December 10, 2025 •

3 min read

A strong, pungent, 'fishy' smell is almost always a sign of spoilage, not freshness, and indicates that bacteria have started breaking down the fish. This guide will explain why is seafood supposed to smell fishy is a common but dangerous misconception.

Quick Summary

Fresh seafood has a mild, briny, or clean ocean-like aroma, not an overpowering fishy odor. The characteristic smell comes from a chemical compound called trimethylamine (TMA) that is produced by bacteria during decomposition. A strong smell signifies spoilage and means the seafood should be discarded, while a clean scent indicates it is safe and of high quality.

Key Points

Freshness Indicator: Fresh seafood should have a mild, clean, briny smell, not a strong or pungent fishy odor.
Cause of Smell: The fishy smell is caused by trimethylamine (TMA), a chemical produced by bacteria breaking down the fish's natural compounds after death.
Signs of Spoilage: Beyond smell, signs of spoiled fish include cloudy eyes, gray gills, slimy texture, and soft flesh.
Smell Removal: Mild fishy odors can be reduced by soaking the seafood in milk or marinating in an acidic liquid like lemon juice.
Prioritize Safety: If the fish smells strongly, sour, or like ammonia, it is spoiled and should be discarded, as cooking will not make it safe.
Proper Storage: To maximize freshness, store seafood on ice in the coldest part of the refrigerator and cook within one to two days.

The Science of the 'Fishy' Smell

Contrary to popular belief, fresh seafood does not have a strong odor. The unpleasant "fishy" smell associated with seafood is the result of natural decomposition. When a fish dies, enzymes and bacteria begin to convert a naturally occurring, odorless chemical called trimethylamine oxide (TMAO) into trimethylamine (TMA). It is this volatile compound, TMA, that gives spoiled seafood its signature odor.

What Fresh Seafood Actually Smells Like

So, what should you look for? Fresh fish, whether from the ocean or a lake, should have a mild, clean, or briny scent. Some varieties of fresh-caught fish may even have no discernable odor at all. This clean smell is the most reliable sign of freshness. If the fish has a strong, pungent, or ammonia-like smell, it is past its prime and should not be purchased or consumed.

How to Identify Spoiled Seafood

Beyond the aroma, several other sensory indicators can help you determine the freshness of seafood. Trusting your senses is the most important step in ensuring food safety. The following list details key signs of freshness and spoilage:

Eyes: For a whole fish, look for clear, bright, and slightly bulging eyes. Cloudy, sunken, or dull eyes are a major red flag.
Gills: Gills should be a bright red or pink, not brown or gray. They should also be clean and free of a slimy film.
Flesh: Press a finger gently into the flesh. On fresh fish, it should spring back immediately and feel firm. If the indentation remains, the fish is likely old. Fillets should look moist and have a clean appearance, not slimy or dried out.
Skin: The skin and scales should be shiny and moist, not dull or discolored.
Shellfish: Live shellfish such as clams, mussels, and oysters should have tightly closed shells. Discard any with shells that are open or that do not close when tapped.

Comparison: Fresh vs. Spoiled Seafood


Feature	Fresh Seafood	Spoiled Seafood
Smell	Mild, clean, ocean-like, sometimes faint cucumber scent	Strong, pungent, ammonia-like, or sour odor
Flesh	Firm, resilient, springs back when pressed	Soft, mushy, leaves an indentation when pressed
Eyes (Whole Fish)	Clear, plump, and shiny	Cloudy, dull, or sunken
Gills (Whole Fish)	Bright red or pink	Brown or gray
Skin	Shiny, moist, and vibrant	Dull, dry, or discolored
Shellfish (Live)	Tightly closed shells	Shells that are open or don't close when tapped

How to Mitigate Fishy Odors

For seafood that may have a slight but not overwhelming fishy odor (not spoiled), there are methods to help reduce the smell. These techniques work by either rinsing the TMA compounds or neutralizing them with acid.

The Milk Bath: Soaking fish fillets in milk for 20 minutes can effectively reduce the fishy smell. Milk contains casein, a protein that binds to the TMA compounds. When you drain the milk, the odor goes with it.
Acidic Marinades: Marinating fish in acidic liquids like lemon juice, lime juice, or vinegar can neutralize the basic TMA compounds. The acid turns the volatile amines into non-volatile salts, which reduces the smell. This is why lemon is a classic pairing for fish.
Rinsing: A quick rinse with cold tap water can help remove some of the surface-level TMA.

Proper Storage is Key to Preventing the Smell

Proper handling and storage are crucial for preventing seafood from developing a fishy odor in the first place. Always store fresh seafood in the coldest part of your refrigerator, ideally at or below 40°F (4°C). For best results, place it on a bed of ice in a shallow pan and use it within one to two days of purchase. Live shellfish should be kept in a breathable container with a damp cloth, as they need to breathe. If you don't plan to use it soon, freezing is the best option for long-term storage.

Conclusion

In short, no, seafood is not supposed to smell fishy. A mild, clean scent is the hallmark of freshness and quality. A strong or unpleasant fishy odor is a reliable sign of bacterial decay and indicates the product is no longer safe to eat. By using your senses—especially your nose—and following proper storage and handling techniques, you can ensure a safe and delicious seafood experience every time. The next time you visit your fishmonger, remember: a clean ocean aroma is what you're after. FoodSafety.gov offers further guidance on proper handling.

Frequently Asked Questions

Fresh seafood does not smell fishy because the compound that causes the odor, trimethylamine (TMA), is not yet present. It only forms as bacteria break down the fish after it dies. Fresh fish should smell mild, clean, and like the ocean.

A bad or spoiled fish will have a strong, pungent, sour, or ammonia-like smell. The odor often intensifies the longer the fish sits.

No, cooking will not eliminate the fishy smell from spoiled seafood. In fact, heat can intensify the odor. Never try to cook or eat spoiled seafood, as it poses a serious risk of foodborne illness.

If you want to reduce a mild, not spoiled, fishy scent, you can soak the seafood in milk for about 20 minutes before cooking. Alternatively, an acidic marinade with lemon juice or vinegar can neutralize the compounds causing the smell.

Fresh fish fillets should feel firm and resilient. If you press the flesh with your finger, the indentation should quickly disappear. Mushy or soft flesh is a sign of an older fish.

For optimal quality and safety, fresh seafood should be consumed within one to two days of purchase. Proper storage on ice in the coldest part of the fridge is crucial during this time.

Some freshwater fish, particularly bottom-feeders, can have a muddy aroma from compounds like geosmin produced by blue-green algae. This is not a sign of spoilage, but it can be neutralized with acidic ingredients like lemon juice.