Since 2006, Sacramento city officials have received $1.78 million from the U.S. government to help salmon spawn in the summer, and they're about to get $650,000 more.
The City Council approved funding last week from the U.S. Fish and Wildlife Service to continue the Lower American River Salmonid Spawning Gravel Augmentation Project.
Tom Gohring, executive director for the City-County Office of Metropolitan Water Planning, the office in charge of the program, said the dams and reservoir on the American River stop the "natural movement of sediment and gravel." He said those items are necessary for successful salmon spawning.
Salmon, like humans, need oxygen to survive, said Lisa Thompson, director for the Center for Aquatic Biology and Aquaculture at UC Davis. That means their eggs need to have access to oxygen, as well, which they get from flowing water.
In the egg-laying process, a female salmon will turn on her side and move her tail up and down to lift out some of the finer materials in the gravel while leaving the larger pieces to fall back down. Eggs are then laid in a nest and covered up with the remaining gravel.
"In so much as a fish can 'hope' for something, fish hope to take out smaller materials in the egg nest so water can flow through more easily," Thompson said.
Depending on temperature, the eggs typically take months to hatch, Thompson said.
Sacramento's gravel augmentation project aims to help those egg-laying efforts, Gohring said.
"Gravel is selected based on size and then run through two sieves," Gohring said, as salmon can't use gravel that is too small or too large for their eggs.
After being washed, the gravel is injected into different areas of the river, where workers attempt to create a "very specifically sculpted habitat," Gohring said.
He said the gravel comes from different areas depending on the year. For the past three years, gravel was taken from Sailor Bar on the American River.
Gohring said there are too many variables in salmon spawning to determine whether or not the project can take full credit for increased salmon numbers during the annual fall run, but he added that, "for doing the job we want the gravel to do, it's been successful."
He said there is a long-term need to place gravel into the American River for salmon spawning, and the project continues on a year by year basis.