What Do Salmon Eat?

Salmon are carnivores. They eat other animals, not plants. Their diet is built on small fish, squid, krill, and shrimp, plus insects and tiny drifting animals called zooplankton when they are young. What lands on the menu depends heavily on the species and on whether the fish is living in a river or the open ocean.

That single fact explains a lot about salmon. It explains why farmed salmon are fed fish-based pellets, why wild salmon flesh turns pink, and why a salmon’s feeding habits shift dramatically over its lifetime. Below is what the evidence shows about what these fish actually eat, and where the picture gets less certain.

What Do Salmon Eat in the Wild?

Adult salmon in the ocean are opportunistic predators. They eat whatever is abundant and the right size to swallow, which in practice means small schooling fish, squid, and crustaceans.

Across species, the ocean diet commonly includes:

• Herring, sardines, anchovies, and other small forage fish
• Sand lance, capelin, and smelt
• Squid
• Krill, shrimp, and other small crustaceans
• Occasionally juvenile fish of other species

The mix varies by region and season. A Chinook salmon in the North Pacific and an Atlantic salmon in the North Atlantic are eating similar categories of prey but not the same species. Salmon do not specialize. They take what is available.

One detail worth clearing up: the “salmon” most people picture is one of several species. Chinook, coho, sockeye, pink, and chum salmon are all distinct, and Atlantic salmon is a different genus entirely. Their diets overlap a great deal, but they are not identical.

What Do Young Salmon Eat?

Young salmon eat tiny prey. A newly hatched salmon, called an alevin, does not eat at all at first. It lives off a yolk sac attached to its body.

Once that yolk is absorbed, the fish becomes a fry and begins feeding on:

• Zooplankton, including water fleas and copepods
• Small aquatic insects and their larvae
• Terrestrial insects that fall onto the water surface

As the fish grows into a parr and then a smolt, its prey gets larger. It moves from drifting microscopic animals to insects to small fish. This progression matters because a young salmon’s ability to find enough food in freshwater partly determines whether it survives the transition to salt water.

How Does a Salmon’s Diet Change Between River and Ocean?

The change is dramatic. In freshwater, salmon eat insects and small aquatic invertebrates. In the ocean, they eat fish and squid. These are not small variations on the same theme — they are different food webs.

This shift is tied to a physiological change called smoltification, when the fish adapts to survive in salt water. Once in the ocean, salmon grow fast on a protein- and fat-rich diet of forage fish. That ocean diet is what builds the mass and energy stores the fish will later need to swim back upriver.

Here is a point that surprises many people. Most Pacific salmon stop eating once they re-enter freshwater to spawn. They live off stored fat and muscle for the rest of the journey, and they die after spawning. Atlantic salmon are different — many can survive spawning and return to the ocean, and they do resume feeding in freshwater to some degree. So the common idea that “all salmon stop eating in rivers” is only true for Pacific species.

Why Is Farmed Salmon Pink If It Eats Pellets?

Farmed salmon are fed formulated pellets, not wild prey. Those pellets are made largely from fish meal and fish oil, along with plant proteins, vitamins, and minerals. The pink-orange color of the flesh comes from carotenoid pigments — mainly astaxanthin — that are added to the feed.

Wild salmon get these same pigments by eating krill and shrimp. The color is not produced by the fish itself. It comes from the diet, whether wild or farmed. This is why the flesh of a salmon that eats no pigment-rich prey would be pale, closer to white or gray.

Farmed salmon diets have shifted over the decades. Early feeds relied heavily on wild-caught fish. Modern feeds use more plant-based ingredients, which has reduced the amount of wild fish needed per pound of farmed salmon. The exact ratios vary by producer and are not something to take a single number for.

Do Salmon Eat Anything Besides Fish and Crustaceans?

Yes, especially in freshwater. Salmon will eat aquatic insects, terrestrial insects that land on the water, and small invertebrates. Some populations take fish eggs and small juvenile fish.

What salmon do not do is graze on plants. They are not herbivores. They do not eat algae, seaweed, or aquatic vegetation as a food source. Any claim that salmon are plant eaters is wrong.

There is also no evidence that salmon eat mammals, birds, or anything large. Their prey is limited by what they can swallow whole. Salmon do not chew. They seize prey and swallow it.

How Do Salmon Find and Catch Their Food?

Salmon are visual hunters in many situations. They locate prey by sight, which is one reason water clarity and light matter. They also use their lateral line, a sensory system that detects movement and pressure changes in the water, to sense prey nearby.

Feeding behavior varies. Some salmon feed in loose groups where prey is concentrated. Others are more solitary. Young salmon in streams tend to hold a position in the current and grab drifting food as it passes, a behavior called drift feeding.

Salmon are not ambush predators in the way a pike is. They are more often described as active foragers that chase or intercept prey. The exact hunting methods differ by species and life stage, and researchers continue to study how much salmon rely on vision versus other senses in murky water.

Does What Salmon Eat Affect Their Nutrition for People?

It does, in a general way. Salmon are a source of protein, long-chain omega-3 fatty acids, vitamin D, and selenium. Those nutrients come from the salmon’s own diet, either wild prey or formulated feed.

Wild and farmed salmon can both be nutritious. The fat content and fatty acid profile differ depending on species, diet, and farming practices, so blanket statements that one is always better are not well supported. Some studies suggest farmed salmon tends to be higher in total fat, while wild salmon tends to be leaner, but values vary widely.

What is well established is that salmon are predatory fish that accumulate nutrients from the animals they eat. That is the direct link between what a salmon eats and what a person gets from eating the salmon.