What is the salmon run?
Because salmon (and steelhead) exhibit an “anadromous” life cycle, we call the return to freshwater from the ocean a run. A species may have multiple runs throughout the year, often tied to the season when they take place. For example, for chinook salmon, a river may have spring, summer, fall, or winter runs (or a combination). For people who rely on salmon, this means that food or cultural celebrations can be available or occur throughout the year. For the fish, this is not a random choice of when to run. Rather, this is an important way they have evolved to minimize competition for quality breeding locations if they all ran at once. Also, by spreading out reproduction, the salmon can maximize their reproductive success.
What types of salmon are we seeing?
During the fall months in the Columbia River (and in the tributaries that feed it), we are most likely to encounter fall chinook and coho runs..
What effects or initiates a salmon run?
There are a couple of environmental cues that trigger a salmon run. Seasonal rains (mostly in spring and fall) increase a river’s flow. As these occur nearly every year, the returning adults have evolved to respond to these increases in flow. Another important cue is water temperature. Temperature is important for development rate and hatching of babies, especially when it is matched with the emergence of their food (aquatic insects and zooplankton, for example). Light (intensity and day length) may also play a role, as these, too, occur similarly every year.
When is the salmon run? And what happens in between?
See answer #1. There isn’t a fine line or exact time when one run ends and the next begins. A run can last for weeks or months; we often look for a run’s “peak.” In some years, depending on flows, temperatures, and other influences, runs can start and end earlier or later, perhaps even overlapping a bit. Other than steelhead, most salmon run and breed only one time.
