How to Tell When Fish Is Done

The safe internal temperature

The USDA and FDA recommend cooking fish to an internal temperature of 145°F (63°C). An instant-read thermometer inserted horizontally into the thickest part of the fillet is the most reliable way to check, because colour and texture can be misleading.

Many cooks prefer salmon slightly less cooked, pulling it at around 125°F (52°C) for a silky, just-translucent centre. That is below the official guidance, so if you are cooking for someone who is pregnant, a young child, an older adult or someone with a weakened immune system, cook fish to 145°F.

Visual signs that fish is done

If you do not have a thermometer, these cues help, especially with thinner fillets:

• The flesh changes from translucent to opaque all the way through. White fish turns milky white; salmon turns from deep orange to a paler, opaque pink.
• The flesh separates easily into flakes when you press it gently with a fork at the thickest part.
• A thin knife or skewer slides in with little resistance.

How to check different types of seafood

Salmon and other oily fish

Check the thickest part. The surface may look done well before the centre, so insert the thermometer or fork in the middle of the fillet. White beads of protein (albumin) appearing on the surface are a sign the fish is close to done or slightly overcooked.

White fish (cod, halibut, haddock, tilapia)

These lean fillets go from moist to dry quickly. Look for flesh that is opaque and just flaking. Thin fillets may need only a few minutes, so start checking early.

Shrimp, lobster and crab

Cook until the flesh is pearly and opaque. Shrimp also turn pink and curl into a loose C shape; a tight O usually means they are overcooked.

Scallops

Cooked scallops are milky white or opaque and firm, with a golden crust if seared.

Clams, mussels and oysters

Cook until the shells open. Discard any that stay closed after cooking. Before cooking, throw away any with cracked or broken shells, or that do not close when tapped.

A rough guide to timing

A common rule of thumb is about 10 minutes of cooking per inch (2.5 cm) of thickness at moderate-to-high heat, such as baking at 400°F (200°C). Treat it as a starting point only: the starting temperature of the fish, the cooking method and the shape of the fillet all make a difference, so always confirm with a thermometer or the visual signs above.

Avoiding overcooked fish

• Bring thick fillets out of the fridge 10 to 15 minutes before cooking so they cook more evenly.
• Fish keeps cooking for a minute or two after it leaves the heat, so take it off as soon as it reaches temperature.
• For uneven fillets, tuck the thin tail end under itself so it is as thick as the rest.

Frequently asked questions

The bottom line

Fish is done at 145°F (63°C), when the flesh is opaque and flakes easily with a fork. Use a thermometer for thick fillets, rely on the visual cues for thin ones and shellfish, and take it off the heat promptly. Try it with our Lemon Herb Salmon with Roasted Potatoes or a quick pan of Garlic Butter Shrimp.