Pacific salmon begin hunting for food almost as soon as they hatch. Their bodies change to move from freshwater lakes and streams as juveniles to the salty oceans. What the salmon eat changes as well.
Researchers carefully study the diet of migrating salmon.This helps hatchery operators like the Cook Inlet Aquaculture Association (CIAA) understand how best to raise juvenile salmon in hatcheries. It also gives commercial fisheries managers insight into why salmon runs are stronger in some years than others.
What salmon eat in fresh water
Sockeye, coho, and king salmon hatch and spend the first part of their life cycles in freshwater lakes and streams until they smolt and prepare to migrate to the ocean. Pink and chum salmon do not hunt for food in freshwater in these early stages because they almost immediately begin migrating to the ocean after they hatch and absorb their yolk sacs.
Salmon raised by CIAA and released as fry find food in lakes and streams. They will eat about anything they can get their mouths around, including small insects and insect larvae, zooplankton, and small crustaceans called amphipods or scuds.
The hatchery salmon diet
Salmon raised in CIAA hatcheries are fed fish feed from Bio-Oregon, a commercial supplier of fish food. This feed comes in different sizes and combinations of nutrients to follow salmon through their growth.
Hatchery food is made with fish meal and fish oil as well as supplemented vitamins to ensure healthy fish. This fish meal and oil can come from different sources, including scraps from commercial processors used to produce these feeds. The rest of the feed production comes from small ocean fish that breed rapidly, such as herring, sardines, and mackerel.
The salt water salmon diet
In the sea, salmon become predators, feeding on a wide variety of creatures. Once in the ocean, a salmon’s main goal is to avoid getting eaten while eating lots to get ready for their migration back to the spawning grounds.
Salmon continue to eat similar foods as they ate in the freshwater, such as zooplankton and crustaceans, but they expand their palate to include small squid, eel, and lots of shrimp.
In many ways, salmon become what they eat in the ocean. Consider the differences between coho, king, and sockeye fillets, particularly their color.
The pink or red color in salmon flesh comes from carotenoids, a natural pigment present in many vegetables such as carrots, tomatoes and pumpkins. Crustaceans such as shrimp and crabs contain high levels of carotenoids.
It makes sense that crustaceans make up the majority of the sockeye’s preferred diet, resulting in that distinct red flesh color. On the other hand, coho and king may feed partially on crustaceans but they also enjoy other small fishes, resulting in flesh that is more orange.
The last fast before spawning
Once adult pacific salmon re-enter fresh water on their way to spawning grounds, they stop eating. This is why it is so important to gather nutrients while in the saltwater. If they are unable to store the energy required to make migration they will not survive long enough to reproduce. While adult salmon are in fresh water, they have one singular goal, reproduce.
