SOUTH LAKE TAHOE, Calif. – On Nov. 3, 2023, the U.S. Forestry Service temporarily interrupted the water flow to Taylor Creek from the Fallen Leaf Lake dam for three days.

This raised concern from community members regarding the spawning kokanee salmon and the future of their eggs.

University of Nevada, Reno Professor Sudeep Chandra says the flow into the lake also attracts kokanee to the stream for spawning and that while this interruption could impact reproduction, another concern is ensuring warm water invasive fish species don’t move across the ecosystem, becoming fully established in Taylor Creek and Fallen Leaf Lake.

He says if invasive warm water fish species were to become fully established in the creek, they would eat the young kokanee, limiting the amount of young that would make it back to the lake and become spawning adults themselves.

The USFS interrupted the flow for three days by closing a culvert at Fallen Leaf Lake that they say the warm water species, including large mouth bass, small mouth bass, crappie, bluegill, catfish ,and even goldfish, could move through and go into Fallen Leaf Lake.

On Nov. 6, the USFS re-established the Taylor Creek flow from Fallen Leaf by causing water to go over the dam, preventing the movement of invasive species into Fallen Leaf through the culvert.

Kokanee salmon are not native species and were introduced into Lake Tahoe in the mid-forties, according to Chanda.  

Information Officer Peter Tira of the California Department of Fish and Wildlife explains they entered the lake on accident after a flood event at a nearby hatchery at the time washed Kokanee salmon into the lake.

In the past, the CDFW has stocked Lake Tahoe with kokanee salmon, but stopped several years ago. The agency would collect eggs from Taylor Creek and fertilize them. This was their primary source for the stocking hatchery for reservoirs around the state. One reason for restocking the lake was to make up for the eggs taken.

Chandra says the fish have been maintained through an artificial process over time anyway, so he doesn’t think anyone should be sweating yet.

“We’ve adopted kokanee as one of the fishes we love in Lake Tahoe even though it’s introduced, but we’ve adopted it and then enhanced and played with it’s population over time by either putting in more eggs or changing flows. So, in this artificial like system,” he says, “I’m not too worried about their longterm prospects of maintaining kokanee in the Lake Tahoe system.”

The CDFW does say that if a severe enough event were to occur to the salmon population, they’d consider stocking the lake again, but they couldn’t unilaterally make that decision and would have to consult their various state, federal, and tribal partners.

Chandra says even if this generation of fish were taken out, there’s plenty of adults still in lake Tahoe living out their lives until they’re ready to spawn themselves.

Tira adds, saying that while Taylor Creek supports the largest spawning run of kokanee from Lake Tahoe, there are other places they can spawn, including other streams and the lake itself.

“So nature has provided Kokanee salmon with different spawning strategies and adaptations” Tira says, “to ensure the species survival.”

Chandra says a larger concern is controlling warm water fish, which once established, can have a huge impact on native fish and be very hard to remove. Since 1960, he reports that Tahoe has seen a 10 fold decline in native fish species.

In addition to pestering and eating native species, blue gill and bass excrete waste that can increase algae growth, so they can impact Tahoe’s clarity, he says, “We don’t want these species there.”

Overall, Chandra isn’t too concerned with the water flow interruptions.

“I think that kokanee salmon are some of most beautiful fish in world and we’re lucky to have them in Lake Tahoe because it brings people together to view such beautiful biodiversity,” Chandra says, “but there is a balance in between trying to keep and maintain an overall healthy ecosystem, while also trying to manage introduced biodiversity, and that’s the top part for the forest service.” 

Tira says initially the CDFW had no knowledge of the USFS Taylor Creek flow interruptions, but have since communicated with the agency regarding the incident. Both agencies have agreed to keep the other apprised of future incidents.

He says the CDFW coincidentally collected 253,000 eggs this fall before the flow incidents since spawning numbers at other collection sites were low this fall.