Salmon are fish known for their journeys between freshwater and marine environments. Their ability to thrive across diverse habitats is linked to their varied diet. Food sources change throughout their lives and depending on their location, influencing their growth, health, and physical appearance. Understanding what salmon eat provides insight into their biology and the ecosystems they inhabit.
Primary Fish Prey
In their marine phase, adult salmon predominantly consume other fish, which constitute a significant portion of their diet by weight. Common prey species include capelin, Atlantic herring, sand lance, barracudina, and lanternfish. These fish are often found in large schools, making them efficient targets. Their high fat and protein content provides energy for salmon’s active lifestyle and demanding migrations.
Herring are a crucial food source, and their size and life stage influence their importance in salmon diets. Sand lance are another frequently consumed fish, recognized for their high nutritional value.
Other Essential Food Sources
Beyond fish, salmon incorporate other organisms into their diet. These non-fish items include crustaceans like krill and amphipods, as well as cephalopods such as squid and octopus. Marine worms can also be a part of their opportunistic feeding habits.
Crustaceans, especially shrimp, can make up a substantial number of individual prey items. Shrimp can represent up to 95% of the food by number, even if they account for less by total weight. These diverse food sources contribute important nutrients that complement the fish-heavy diet.
How Diet Influences Salmon
The diet of a salmon profoundly impacts its biological characteristics and life cycle. The type and quantity of food consumed directly affect their growth rate and overall health. Adequate nutrition is necessary to build energy reserves, which are necessary for their strenuous migrations and spawning activities.
The distinctive pink or red color of salmon flesh originates from carotenoids, particularly astaxanthin, found in their diet. This pigment is abundant in crustaceans like shrimp and krill. Astaxanthin is also an important antioxidant that supports the salmon’s metabolic, muscle, and immune functions, providing benefits beyond just energy.
Diet Variations by Life Stage and Habitat
A salmon’s diet changes as it progresses through its life stages and moves between different habitats. In freshwater, young salmon, known as fry, primarily feed on small insects such as mayflies, stoneflies, and caddisflies. They also consume zooplankton and other small invertebrates. As they grow, they may also eat small amphibians and other fish.
Upon migrating to estuaries, their diet transitions to small crustaceans, larval fish, and other small invertebrates. Once in the open ocean, adult salmon become opportunistic predators, consuming larger fish, squid, and other marine organisms. The specific prey available in different ocean regions influences their diet.