Fall is upon us and wherever you live, you are likely to come across news or information about the return of the salmon! Pacific salmon have already begun their long and arduous journey inland and are slowly making their way past the many stream-based obstacles, natural and man-made, in pursuit of their ancestral spawning grounds. Salmon are anadromous, which means that they must migrate upstream from saltwater to spawn, or reproduce, in freshwater.
To begin their journey, salmon must prepare to transition from the salty water of the Pacific Ocean to the freshwater of California’s streams and tributaries, a complex biological process preceded by a change in water temperature and flow from the rivers used for this migration. Depending on the river, salmon may travel a few hundred yards or many miles to reach their spawning grounds.
Salmon spawning requires a very specific set of circumstances, including cool, rapidly flowing and oxygen-rich water, loose gravel of the right size, bankside cover and limited disturbance. Once the female salmon has identified the ideal location, she will use pulses of water from her powerful tail to “excavate” patches of gravel, known as redds, where she will deposit her eggs. The process is followed closely by fertilization of the eggs by the male salmon, after which the female will move upstream to begin the process once again. The loosened gravel provides a series of small crevasses in which the eggs can settle while still receiving oxygen from the cool, rapidly flowing stream, and cover for the young, known as alevin, when they emerge from the eggs in the spring. Salmon may lay between 2000 and 6000 eggs, of which only 5% or fewer will survive to adulthood. Once spawning has taken place, adult salmon from most species will die, providing a tremendous influx of nutrients to the streams where they spawn and feeding numerous other riparian species, from birds and mammals to bacteria and aquatic invertebrates.
The fall is a great time to view the epic salmon journey while visiting local waterways and to see first-hand the process of migration, spawning and the returning of resources to the nutrient cycle through decomposition. This is also prime-time to see other riparian species in their fall activities. Be sure to bring your camera and to “tread lightly” while enjoying the conclusion of the epic salmon migration, wherever you might be!
Salmon and Wildlife Viewing Recommendations
Give salmon and other wildlife plenty of space. Salmon are most vulnerable during spawning season and may feel threatened if viewed too closely. Bring binoculars and viewing equipment and be sure to stay back from spawning salmon to encourage natural behavior.
Stay out of the streams. Walking through streams can damage redds, compress gravel, crush eggs or reduce oxygen flow over the eggs.
Take only pictures. Removing material from activate nesting or feeding sites may disrupt animal behavior. Pictures will last much longer anyway!
Dress warmly. Be prepared for cold and wet weather and other environmental conditions that are typical of fall and winter months.
Keep dogs on leash. Dogs may try to eat salmon carcasses or interfere with spawning. Best to keep them away from salmon and other wildlife activities.
Have you seen a salmon?
Report your observation here. Researchers are looking for reports of live and dead fish - any information is helpful!