Salmon are known for their life cycle that involves both freshwater and marine environments. Their diet is fundamental to their survival, fueling their growth, development, and extensive migrations. It also drives physiological changes and provides energy reserves needed for reproduction.
What Young Salmon Eat in Rivers
Young salmon, in their fry and parr stages, begin life in freshwater rivers and streams. After absorbing their yolk sac, fry feed on microscopic invertebrates and small insects.
As they mature into parr, they become more active predators. Their diet expands to include aquatic insects like mayfly, stonefly, caddisfly, and blackfly nymphs and larvae. They also consume small crustaceans such as amphipods and zooplankton. Larger parr may even eat small amphibians, other fish, or fish eggs. This freshwater diet is critical for their early growth and development before adapting to saltwater.
The Ocean Diet of Adult Salmon
Once salmon migrate to the ocean, their diet diversifies due to abundant marine life, allowing rapid growth. Adult salmon become active predators, consuming a wide variety of prey. Their primary food sources include smaller forage fish such as herring, anchovies, sand lance, capelin, barracudina, and lanternfish. They also feed on crustaceans like krill and shrimp, along with squid and polychaete worms. This energy-rich marine diet allows salmon to accumulate the substantial fat reserves necessary for their return to freshwater.
Salmon’s Spawning Fast
Salmon stop feeding once they begin migrating back to freshwater spawning grounds. This journey, which can span hundreds of miles and last several months, relies entirely on energy stored from their time in the ocean. Salmon use fat reserves as fuel for migration, gonad development, and the demands of spawning. Their bodies draw down these fat stores to sustain themselves through the reproductive process.
Factors Affecting Salmon’s Diet
Several factors influence what salmon eat throughout their lives. Different salmon species exhibit distinct dietary preferences; for example, Sockeye salmon primarily consume zooplankton, contributing to their red flesh, while Chinook salmon favor other fish and squid.
The size and age of a salmon dictate the type and size of prey it can effectively pursue and consume. As salmon grow, they shift from smaller invertebrates to larger fish.
The availability of prey in their habitat plays a direct role, as geographic location determines accessible food sources. Water temperature also affects their diet by influencing the metabolism of both salmon and their prey, and the overall productivity of the ecosystem. Warmer temperatures can increase metabolic demands, requiring more food, but may reduce prey availability or nutritional content.