Salmon get energy through eating and respiration.
Eating
Salmon are carnivores. Their diet includes insects, smaller fish, shrimp, crustaceans, and sometimes plankton. After digestion, nutrients are absorbed into the bloodstream.
Respiration
They take in oxygen through their gills. Inside cells, oxygen combines with nutrients in cellular respiration to produce ATP, the energy used for swimming, growth, and reproduction.
Energy Storage
Salmon store excess energy as fat, which fuels demanding migrations, especially the upstream journey to spawn.