Salmon stop eating in freshwater primarily because they need to conserve their energy for the arduous journey of returning to their home stream, reproducing, and creating a suitable nest for their eggs. This behavior is seen in Pacific salmon, which includes species such as Chinook, coho, chum, pink, and sockeye salmon.
When salmon return to freshwater from the ocean, they undergo several physiological changes in preparation for spawning. One of these changes is the reabsorption of their digestive system, rendering them unable to digest food effectively. This means that even if they were to continue feeding, their bodies would not be able to extract the necessary nutrients from their food.
Instead, salmon rely on the energy reserves they have built up during their time in the ocean. They use these reserves to navigate upstream against strong currents, leap over obstacles such as waterfalls, and find suitable spawning grounds. It is a physically demanding process that requires all their energy and strength.
Furthermore, the process of spawning itself is incredibly taxing on the salmon’s body. Female salmon dig nests, known as redds, in gravel beds using their tails, while males compete for the opportunity to fertilize the eggs. This activity requires a significant amount of energy and stamina.
Once the spawning process is complete, many salmon die shortly after. The exhaustion from the journey, the physical strain of reproduction, and the lack of food all contribute to their declining health. Some salmon may survive to make the journey back to the ocean, but their energy reserves are typically depleted, making it difficult for them to find food and survive for long.
It is important to note that this behavior is specific to Pacific salmon and may not be the same for all species of salmon. For example, Atlantic salmon can undergo multiple spawning cycles and may continue to feed in freshwater after their initial spawning.
Salmon stop eating in freshwater because their bodies undergo physiological changes that prevent effective digestion. They need to conserve their energy for the demanding tasks of returning to their home stream, reproducing, and creating a suitable nest for their eggs. This behavior is specific to Pacific salmon and is a crucial part of their life cycle.