Which Fish Are Considered Red Meat? The Surprising Science of Seafood Color

December 26, 2025 •

4 min read

Experts agree that the color of a fish's flesh is primarily determined by its muscle composition and diet. While many are considered white meat, a few popular species defy this common perception, prompting the question of which fish are considered red meat. The answer lies in their unique biology.

Quick Summary

Fish with high levels of myoglobin, the oxygen-storing protein, have red flesh due to their active, migratory lifestyles. Examples include tuna and mackerel. The classification differs from salmon, whose color comes from diet, not myoglobin.

Key Points

Tuna and Mackerel: These fish are considered true red meat fish due to high myoglobin, a protein for oxygen storage that darkens muscle.
Salmon's Exception: Salmon's pink color comes from consuming astaxanthin, a carotenoid pigment found in crustaceans like krill, not from myoglobin.
Activity Level Dictates Color: Active, migratory fish have red flesh (slow-twitch muscle), while sedentary fish have white flesh (fast-twitch muscle).
Not All Tuna is Equal: Different tuna species vary in color; albacore has whiter flesh than the deeper red of bluefin or yellowfin.
Nutrient-Dense Options: Red-fleshed fish are often richer in omega-3 fatty acids and iron than their white-fleshed counterparts.
Flavor Profiles: Red meat fish have a richer, meatier flavor, while white fish are milder and flakier.

The Science Behind Fish Color: Myoglobin and Muscle

Unlike land animals, whose muscles support their body weight, fish muscles are adapted primarily for propulsion. The color of a fish's flesh is a direct result of its activity level and the corresponding composition of its muscle fibers. The key protein involved is myoglobin, which stores oxygen within muscle cells. Fish that are constantly on the move, like migratory swimmers, have a higher concentration of myoglobin in their slow-twitch muscles, leading to a darker, redder flesh. In contrast, less active fish, which rely on bursts of energy for quick movements, have more fast-twitch muscle fibers with less myoglobin, resulting in white flesh.

Another source of coloration in fish, entirely distinct from myoglobin, is the fish's diet. Certain species consume crustaceans like krill and shrimp that are rich in carotenoid pigments, such as astaxanthin. These pigments are absorbed and deposited in the fish's muscle tissue, giving the flesh a reddish or pinkish hue, as famously seen in salmon.

The True Red Meat Fish: Myoglobin is Key

When asking which fish are considered red meat, the most scientifically accurate definition points to species with high myoglobin content. These fish are powerful, long-distance swimmers that require a constant supply of oxygen to their muscles, giving their flesh a deep red appearance, similar in principle to the red meat of land mammals.

Notable Examples of Myoglobin-Based Red Fish

Tuna: One of the most famous red meat fish, tuna species like bluefin, yellowfin, and bigeye are known for their deep red flesh. Their constant, fast swimming in the open ocean demands immense oxygen storage in their muscles.
Mackerel: Another migratory powerhouse, mackerel possesses a high myoglobin content that gives its flesh a darker color. Atlantic mackerel, for instance, has red outer meat and white inner meat, reflecting the different muscle types used for continuous swimming versus bursts of speed.
Bonito: Belonging to the same family as mackerel and tuna, bonito is another oily, red-fleshed fish known for its intense flavor.
Swordfish: Similar to tuna, swordfish are large, open-ocean predators with high myoglobin levels, classifying them as red meat fish.

The Colorful Exception: Diet-Dependent Salmon

Salmon is frequently mistaken for a red meat fish because of its vibrant pink or reddish-orange flesh. However, unlike tuna, this color is not due to myoglobin but is entirely derived from its diet.

Astaxanthin Pigment: Salmon consume krill and other crustaceans that contain astaxanthin, a carotenoid pigment. The salmon's body absorbs this pigment, and it is stored in the muscle tissue, producing its characteristic color.
Color Variation: The intensity of the color depends on the type of salmon and its diet. Wild sockeye salmon, which eat a lot of krill, are known for their bright red flesh, whereas farmed salmon's color is often controlled by adding astaxanthin to their feed.

Nutritional Differences: Red vs. White Fish

The biological differences between red and white fish translate into distinct nutritional profiles. The rich muscle composition of red fish means they generally contain higher levels of healthy fats and certain nutrients.

Comparing Myoglobin-Based Red Fish and White Fish


Feature	Myoglobin-Based Red Fish (e.g., Tuna, Mackerel)	White Fish (e.g., Cod, Haddock)
Color Source	High myoglobin concentration in slow-twitch muscles.	Low myoglobin, composed mostly of fast-twitch muscles.
Fat Content	Generally higher in healthy fats, particularly omega-3s.	Lower in fat, making them leaner protein sources.
Nutrient Profile	Rich in omega-3 fatty acids (EPA and DHA), B vitamins, and iron.	High in protein, low in fat, and a good source of minerals like selenium.
Muscle Activity	Continuous, long-distance swimming; highly active lifestyle.	Sedentary or rely on short, quick bursts of movement.

Red-fleshed fish, especially species like mackerel, provide significantly more omega-3 fatty acids per serving than many white fish. They also contain higher levels of minerals like iron due to their oxygen-storing myoglobin. While white fish offer a great source of lean, high-quality protein, the fatty acid profile of red fish is especially beneficial for heart and brain health. Ultimately, both red and white fish offer valuable nutritional benefits and should be included in a balanced diet.

Cooking and Culinary Considerations

The color and composition of fish meat also influence how it behaves in the kitchen. Red meat fish like tuna have a robust, meaty flavor and texture that can be seared like a steak, leaving the inside rare. Lighter, white-fleshed fish have a milder flavor and delicate flake, requiring less assertive cooking methods to preserve their texture and taste.

Conclusion: Defining Red Meat in the Ocean

The term "red meat fish" is not a single, consistent classification but depends on the biological reason for the flesh's color. True red meat fish, such as tuna, mackerel, and bonito, get their hue from high concentrations of myoglobin needed for their active, migratory lifestyles. Salmon, however, receives its pink coloration from pigments in its diet, not from myoglobin. Understanding this distinction is key to appreciating the diversity of seafood. Both myoglobin-rich and diet-colored fish offer distinct flavors and nutritional benefits. The best choice depends on your culinary goals and specific dietary needs.

For additional information on sustainable seafood choices, consider visiting the Marine Stewardship Council.

Frequently Asked Questions

Tuna is considered red meat because it is a highly active, migratory fish that requires a large amount of oxygen for its muscles. This leads to a high concentration of the oxygen-storing protein myoglobin, which gives the flesh its deep red color.

No, salmon is not a true red meat fish in the same biological sense as tuna. Its pinkish-red color comes from a carotenoid pigment called astaxanthin, which it gets from its diet of crustaceans like krill, not from myoglobin.

Myoglobin is an iron-containing protein that stores oxygen in muscles and is the cause of redness in animals like tuna and beef. Astaxanthin is a dietary pigment that is absorbed and stored in fat tissue, giving species like salmon and flamingos their pink color.

Yes, mackerel is classified as a red meat fish. As a migratory species, it has a high myoglobin content to support its endurance swimming, giving its outer meat a reddish hue.

Farmed salmon do not have access to the natural diet of krill and crustaceans that color wild salmon. As a result, astaxanthin is typically added to their feed to give them their desired pink flesh.

Neither is definitively healthier; they have different nutritional profiles. Red fish is generally higher in omega-3 fatty acids and iron, while white fish is typically leaner and lower in calories. The best choice depends on your specific nutritional needs.

Fish flesh turns white when cooked because the heat causes the muscle proteins to coagulate and become opaque. This happens regardless of the initial color, though red meat fish like tuna may appear less white and can retain some pinkness when cooked rare.

White fish are typically sedentary species with low myoglobin levels and include cod, haddock, tilapia, flounder, and sea bass.