Boaters and fishermen who visit the Stanislaus River above New Melones Reservoir might be surprised to see hundreds of dead fish littering the shores.
Officials say the carcasses near Camp 9 are part of a natural phenomenon that takes place in the fall - the kokanee salmon spawn.
"Those are kokanee that normally die after spawning," said Pete Lucero, spokesman for the Bureau of Reclamation, which manages the lake.
Kokanee are landlocked sockeye salmon, which are native to the Pacific Northwest. The California Department of Fish and Game stocks New Melones with the popular game fish, as well as Huntington, Pine Flat, Shaver, Bass, Don Pedro, and McClure reservoirs, as well as Lake Tahoe.
The landlocked kokanee are smaller than the ocean-going sockeye, about 16 inches, but the holdovers will still travel upstream to spawn after maturing in the lake's deep, cold water. The fish turn a reddish color and form a hooked jaw during the spawn.
Lucero said the bureau has beentracking the autumn spawn.
"That's a normal occurrence in that area," Lucero said. "If there is something other than kokanee out there, we have not heard of it."
According to Fishbio, a fisheries research company, kokanee were first introduced to California reservoirs from Idaho in the 1940s.
The salmon is popular with sportsmen, and there's even an annual Kokanee Salmon Festival at Lake Tahoe every fall.