The Columbia River Basin provides vital habitat for chinook, coho, chum, sockeye, pink, and steelhead. Salmon hatch in freshwater rivers and tributaries, where they grow for a year or two. After that, they migrate to the ocean. The majority of their lives are spent in the saltwater; anywhere between two and eight years depending on the species and conditions. Finally, they return to the river to spawn and die.
Many factors affect salmon survival, and the fish face tough odds. Only a tiny percentage of all salmon hatched will live to become adults. That is why female salmon carry thousands of eggs. It’s nature’s way of dealing with a challenging life-cycle and naturally high mortality. In fact, the highest mortality occurs when the eggs hatch and the alevins emerge from the gravel.
For adults, ocean conditions are a major factor in the success or failure of salmon returns. Long term and short term changes in climate, atmospheric pressure, and water temperature create ocean conditions that are sometimes favorable to salmon survival and sometimes not. They are also an essential part of the oceanic food chain—consumed by other fish, sharks, whales, and birds. Other natural predators, such as cormorants, terns, and sea lions, have increased their consumption in recent years. Pollutants and toxins take their toll as well, from plastics to prescription medications.
Destruction and loss of habitat has also been an issue for salmon, particularly in fresh water. Poorly constructed culverts and dams lacking fish passage have blocked access to many spawning grounds. Commercial and sport fishing is heavily regulated to minimize its impacts, but over-fishing decades ago had a major hand in the decline of salmon populations.