How to Tell If Seafood Is Fresh: Visual and Smell Cues for Fish and Shellfish

Why Freshness Is a Safety Issue, Not Just a Quality Preference

Fresh seafood spoils quickly because fish and shellfish are highly perishable. Bacteria and enzymes start breaking down tissue soon after harvest, and the signs of that breakdown are visible and olfactory long before the food becomes dangerous. Learning to read those signs helps you avoid both waste and foodborne illness.

This guide focuses on raw fish and shellfish you buy from a market or seafood counter. It covers whole fish, fillets, shrimp, scallops, and bivalves like clams, mussels, and oysters. The cues are visual and olfactory; they do not require special equipment. When in doubt, remember that fresh seafood should smell like the sea, not like fish.

If you are cooking seafood that was frozen, the same cues apply after thawing, but note that freezing changes texture and color slightly. For thawing guidance and safe cooking temperatures, see the sibling articles on this site. This article is about what to look for before you cook.

• Smell: fresh = mild sea breeze; spoiled = sour, ammonia-like, or strongly fishy
• Touch: fresh flesh springs back; spoiled flesh stays indented
• Eyes: clear and bulging in whole fish; cloudy or sunken means old
• Gills: bright red or pink; dull brown or gray means aging

Whole Fish: Read the Eyes, Gills, and Skin

A whole fish gives you the most information. Start with the eyes. In a fresh fish, the eyes are clear, bright, and slightly bulging. As the fish ages, the eyes turn cloudy, gray, and eventually sink inward. This is one of the most reliable indicators because it changes quickly and is hard to disguise.

Next, lift the gill cover. Fresh gills are bright red or deep pink and moist, with a clean, mild scent. Dull brown, gray, or slimy gills indicate the fish is past its prime. The skin should be shiny and metallic-looking, with tightly attached scales. Dull, dry skin or loose scales are warning signs.

Press the flesh with a finger. Fresh fish is firm and springs back when you press it; if the indentation remains, the flesh is softening. The belly should be intact and not bloated. A sunken or torn belly suggests the fish was not handled well and has begun to decompose.

Fillets and Steaks: Color, Texture, and Odor

Fillets and steaks are cut away from the bone, so you lose the clues of the eyes and gills. Instead, rely on color, texture, and smell. Fresh fillets look translucent and moist, with flesh that is firm to the touch. The color varies by species—salmon is orange-pink, tuna is deep red, white fish is pearly white—but it should be even and vibrant, not dull or brown at the edges.

Run a clean finger across the surface. It should feel slick but not slimy. A fillet that feels sticky or leaves a film on your finger is beginning to spoil. The flesh should be tightly packed, not separating into flakes. If you see gaping or the fillet is falling apart, it is old.

Smell is the most direct test. Fresh fillets have a mild, briny scent reminiscent of the ocean. Spoiled fish smells sour, like ammonia, or unpleasantly fishy. The ammonia smell is especially noticeable in shark and other cartilaginous fish, but it appears in all fish as they break down. If the smell makes you hesitate, do not buy it.

Shellfish: Shrimp, Scallops, and Bivalves

Shrimp should have a mild, slightly sweet smell and a firm, translucent body. The shells should be intact and not slimy. If the shrimp smell like ammonia, that is a clear sign of spoilage. Fresh shrimp have a clean, briny aroma; any off-odor means they are past their prime. The meat should be firm, not mushy.

Scallops are sold either wet or dry. Dry scallops are naturally moist and have a sweet, clean smell. Wet scallops are soaked in a phosphate solution to retain water, which makes them look plump but gives a soapy or chemical odor. For freshness, look for dry scallops with a sweet scent and firm texture. Avoid any scallop that smells sour or fishy.

Bivalves—clams, mussels, and oysters—are alive when sold. Their shells should be closed, or they should close when tapped. A shell that remains open is dead and should be discarded. Fresh bivalves smell like the ocean, not like low tide. They should feel heavy for their size, indicating they are full of seawater. If the shells are cracked or broken, they are not safe.

How to Test Freshness at the Counter

When you are at a seafood counter, you can do more than look. Ask to smell the fish. A reputable seller will not mind. If the display case smells strongly fishy, that is a red flag—it should smell clean and cold. The seafood should be displayed on ice or in a refrigerated case below 40°F (4°C).

Check the ice. If the fish is sitting in melted water rather than on ice, it has been thawing and may be old. The flesh should not be sitting in liquid. For whole fish, you can also gently press the belly; it should be firm, not soft. If you are buying fillets, ask when they arrived. Many markets label the arrival date.

Trust your senses. Fresh seafood is visually appealing, smells clean, and feels firm. If any cue is off, walk away. Spoilage bacteria can cause food poisoning, and cooking does not always eliminate the toxins they produce. When in doubt, choose something else or buy frozen, which can be a high-quality option if handled properly.