A study found sturgeon were spawning at four sites, and that they spawned during both wet and dry years in 2011 and 2012.
White sturgeon are thought to be found only in three major river systems on the West Coast.
"It’s important for a species to be able to spawn in multiple locations to be able to withstand changes in their environment," says Zachary Jackson, a fish biologist with the US Fish and Wildlife Service, who led the study.
"So documenting them in the San Joaquin River and the fact that that might be an important source of production for the greater Central Valley white sturgeon population was pretty important,” says Jackson.
He says California’s green and white sturgeon can be easily over exploited because they mature late and spawn infrequently.
Jackson says biologists will next study whether the sturgeon eggs are hatching and if juveniles are surviving.