Muscle fibers in fish are constructed of very short bundles (up to ten times shorter than the long muscle fibers in meat). And, compared to meat, fish muscle contains only a small fraction of connective tissue, which sits in very thin sheets perpendicular to the muscle bundles.
What does this all mean? To put it plainly, fish are more sensitive to heat! Here are some ThermoWorks recommended temperatures for a few of our favorite cuts:
Salmon – 125°F
Salmon – like all fish – has almost no collagen, which means it will start to lose moisture more quickly than beef. While the FDA recommends cooking fish to 145°F, for a flakier, more moist and tender salmon filet many chefs find that it’s best enjoyed when it’s cooked to medium – 125°F.
Halibut – 130°F
Halibut is a very firm fish and holds together well in cooking. This makes it particularly good for grilling. Too often it is overcooked and dry – the center should be just becoming opaque. It is done when it reaches an internal temperature between 130 and 135°F.
Lobster – 140°F
Cooking lobster is straightforward. But like most all seafood, due to its tightly-bound muscle structure and lack of the lubricating fat that makes cooking meat a more forgiving process, lobster cookery can go wrong easily. You want to cook lobster just through. Cooking it too much makes for a rubbery, dry and unfortunate situation, and too little will result in an odd texture and undeveloped flavors.
When grilling, many sources* recommend cooking lobster to a minimum internal temperature of 140°F and serving immediately. However, when boiling or steaming, Cook’s Illustrated suggests taking the internal temperature to 175°F, because the muscle fibers in lobster are longer and require more heat to shrink.
Scallops – 130°F
Because scallops are a lean protein source they should be cooked quickly under high heat and require some fat (such as oil or butter) during cooking. Cook to 130°F internal temperature until the flesh is milky white, or opaque and firm.
Shrimp – 120°F
Constriction is the tell-tale sign that you’ve overcooked your shrimp. The longer you cook them, the tighter and tougher they will get. Look for a change in color (light pink) and an internal temperature of 120°F to tell you when your shrimp are ready to come off the heat. A miniature needle probe is perfect for checking the internal temperature of shrimp.
Ahi Tuna – Rare – Below 115°F
Tuna is most often served rare or seared rare because the longer you cook it, the more flavor and moisture it loses. Tuna cooked rare is optimal in order to maintain flavor and moisture. Raw tuna frequently carries a parasite, but “Sashimi” grade fish has been flash frozen to kill any parasites. Restaurants that serve raw tuna are required to use Sashimi grade.
*McGee, Harold. “On Food and Cooking: The Science and Lore of the Kitchen.” (pg. 220)