Welcome to our new Fish Factors Mini-Series! Each quarter we will share important stories on factors impacting Upper Columbia salmon and trout!
Salmon and steelhead have complex life cycles and over the course of their lives, an individual will occupy many different habitats. Each habitat requires its own suite of adaptations for salmon to survive that life stage. This is the first of four short articles in which we will describe a different salmon life stage, including the adaptations that allow salmon to survive that stage and the factors that affect survival during that time.
Pacific salmon are known for their remarkable upstream migrations from the ocean to their natal, or home waters to reproduce. Salmon use olfactory cues (smells), learned during their seaward migration as juveniles, to guide their upstream migration, often returning to the same location where they were born. Once adult salmon begin this homeward migration, they cease feeding and all subsequent activity must be fueled by the amount of energy they stored while in the ocean. Pacific salmon returning to spawning grounds in the upper Columbia region swim upstream approximately 500 river miles and gain 2,000 feet of elevation. Spring Chinook often travel at a rate of 20-40 miles per day, a journey that requires 40-50% of their total energy, in the range of 11,000 calories (that’s about 20 big macs for you who were wondering).
During their upstream migration, salmon and steelhead must contend with numerous obstacles and potential threats including predation, commercial and recreational fisheries, and variable river conditions. Anadromous fish returning to the Wenatchee and Methow rivers use fish ladders to pass over multiple large dams in the mainstem river. Fish that take longer to pass over dams have a lower chance of completing their migration than fish that pass dams quickly. In recent years, the number of California and stellar sea lions that feed on adult Chinook salmon and steelhead in the lower Columbia River have increased dramatically, and early-migrating populations such as spring Chinook returning to the Methow River, are particularly vulnerable. Another challenge for migrating salmon includes elevated temperatures, which can cause physiological stress and increase susceptibility to diseases. Researchers are working to understand how changing conditions, such as increased sea lion abundance and higher stream temperatures, affect Pacific salmon survival during migration, and fisheries managers monitor numbers of returning fish and impose catch limits to ensure that Upper Columbia salmon continue to make this remarkable journey home.