Science Spotlight

One of twenty-four 270 gallon totes of 10% Hydrogen Peroxide staged for raceway application. Hydrogen peroxide is used to kill the L. garvieae bacteria.


Fish and Wildlife Technician at Mojave River Hatchery applying Hydrogen Peroxide to raceways. Over 224,000 square feet of raceway were treated between the three hatcheries.


Fish and Wildlife Technician at Mojave River Hatchery in his Personal Protective Equipment preparing to disinfect the raceways with Hydrogen peroxide.


Hatchery worker cleaning debris from the hatchery settling pond to prepare for disinfection. Hatchery staff removed several yards of debris by hand to prevent tearing the rubber liner used to protect local ground water.


Hatchery worker spraying hydrogen peroxide on the settling pond liner to kill L. garvieae bacteria.

Eight months after a bacterial outbreak in CDFW fish hatcheries led to the massive depletion of stocks, state fisheries biologists are still working hard on recovery efforts and a plan to stock California’s waters for anglers in 2021 and beyond.

Prior to the initial discovery at the Mojave River Hatchery in April 2020, the bacteria, Lactococcus garvieae, had not been found in California in aquaculture facilities or in the wild. Extensive testing of all CDFW hatcheries found the bacteria to be present in fish at the Fish Springs Hatchery and Black Rock Hatchery as well. Fish at all three hatcheries were immediately quarantined and ultimately 3.1 million trout were euthanized after treatment efforts were unsuccessful.

Over the following months, the three hatchery facilities have undergone intensive disinfection and a team of scientists has been working to test a vaccine developed to prevent infection from the bacteria. Meanwhile, fisheries managers at other state trout hatcheries are working on a joint effort to realign how the trout stocks statewide will be apportioned in order to continue to provide angling opportunities.

Most of the trout affected by the outbreak were destined for Eastern Sierra and Southern California waters. Seven state hatcheries not affected by the bacteria instituted a redistribution plan of healthy fish stocks making trout available to a subset of priority waters normally planted by the hatcheries that were quarantined.

Another priority has been to find or develop an effective vaccine, according to Jay Rowan, CDFW Statewide Hatchery Program Manager. Dr. Mark Adkison of CDFW’s Fish Health Laboratory is leading the state’s efforts in coordination with Dr. Esteban Soto of the UC Davis Aquatic Animal Health Lab in the UC Davis School of Veterinary Medicine. Although there are commercially produced vaccines available, scientists found that they most likely would not protect fish against the genetically distinct strain of L. garvieae bacteria affecting the fish in California’s hatcheries. Together, the scientists have been focused on making an “autogenous” vaccine, produced with the strain of L. garvieae bacteria that is unique to California. The vaccine is currently undergoing laboratory trials.

While the vaccine is being developed, hatchery managers have been hard at work disinfecting the affected facilities. After specialists from UC Davis ran experimental treatment scenarios to determine the most effective disinfectant options, CDFW was able to select and enact a comprehensive treatment plan. All surfaces and equipment were thoroughly cleaned and then disinfected with hydrogen peroxide at a concentration shown to remove biofilms and inactivate the bacteria. These measures were completed in December.

CDFW Fish Hatchery Manager Paco Cabral describes the effort as “lots of work.” Cabral was in charge of the massive and meticulous cleaning regimen to remove the bacteria from Mojave River Hatchery. Every surface that has come into contact with hatchery water requires disinfection -- including the hatchery building tanks, raceway holding ponds, settling ponds, pipes and all related fish rearing and planting equipment, and fixtures such as screens, nets and planting trucks. Even the staff’s waders and boots have to be disinfected.

To cleanse 6,000 feet of concrete raceways, staff utilized a 250-gallon high pressure spray washer to clean algae and dirt off each of the 10-foot by 1,000-foot structures. Once this is complete, backpack sprayers are used to apply a mixture of water and hydrogen peroxide to break down and kill the bacteria. Without these extensive measures, the bacterial will form a protective biofilm allowing it to survive even in the harsh dry conditions of the Mojave Desert in the summer and freezing cold conditions in Eastern Sierra in the winter.

Inside the hatchery buildings, all surfaces -- from incubation structures, tables and trays to faucets and hoses – must be disinfected. The cleaning process also includes all the hatchery plumbing, which is disinfected with the same hydrogen peroxide solution delivered via a gas-powered, high-pressure drain cleaner.

Over the summer, CDFW launched Phase 1 of the stocking plan by reallocating 40,000 catchable fish from central and northern California hatcheries to 16 waters in the Eastern Sierra and Southern California that would have normally been stocked by the infected hatcheries. Decisions about which waters would be stocked were not made lightly; fisheries managers carefully evaluated all options and selected locations based on angler accessibility and suitable water temperatures. Justin Kroeze, Fish Hatchery Manager at Moccasin Creek Hatchery, reports that during July, August and September, the staff from his hatchery were able to plant east side waters with 12,000 pounds of trout.

In Phase II of the stocking plan, which took place in October and November, CDFW reallocated and completed planting approximately 30,000 sub-catchable brown trout and 125,000 sub-catchable rainbow trout from American River Hatchery near Sacramento to Eastern Sierra waters. These fish are intended to be “put and grow,” available to anglers for the spring 2021 trout openers. They were reallocated from the June 2020 high elevation air plants that were cancelled due to staff safety concerns for COVID-19.

In December, Moccasin Creek Hatchery and San Joaquin Hatchery transferred approximately 125,000 rainbow trout to Fillmore Hatchery for stocking into Southern California waters during the December-through-March timeframe. These transferred fish join the approximately 500,000 rainbow trout already at Fillmore Hatchery that are getting close to reaching planting size. Moccasin Creek Hatchery plans to transfer an additional 40,000 rainbow trout to Fillmore in the coming weeks to assist in stocking efforts.

“It feels good to be able to help out the closed hatcheries and plant fish for the anglers in the Eastern Sierra and Southern California,” Kroeze said. “We’ve been in a similar situation here at Moccasin with no fish to plant, so we understand the situation they are in.”

Anthony Holland, Fish Hatchery Manager at Fillmore Hatchery, said that his staff are working to do everything possible to provide fishing opportunities for anglers in Southern California by planting out and holding incoming fish from the northern hatcheries. These plants are being posted on the CDFW trout planting schedule one to two weeks prior to the stocking date.

“We’re getting these fish out as fast as we can to provide angling opportunities to Southern California,” Holland said. “It’s been a while since these waters have been planted, so it’s great to see fish going in and people catching fish.”

In addition, Moccasin Creek Hatchery and San Joaquin Hatchery are holding approximately 400,000 sub-catchable trout for future transfer to the three depopulated hatcheries to help give them a jump start in their efforts to return to planting the waters in their areas in 2021. These trout were made available due to the decision last year to hold and grow extra trout at Moccasin Creek Hatchery once the hatchery came back online after major flood repairs were completed. Once the three affected hatcheries are back online, the number of waters planted will increase dramatically as an annual cycle of rearing is completed. It takes approximately 9 months to 18 months to rear a trout to one-half pound, which is the targeted size for catchable planting.

For additional information, please see CDFW’s frequently asked questions about the L. garvieae outbreak (PDF). Please email questions to hatcherybacteriainfo@wildlife.ca.gov.

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Media Contact:

• Harry Morse, CDFW Communications, (208) 220-1169
• Jay Rowan, CDFW Hatchery Program, (916) 212-3164

CDFW Photos

Luis Santana, fisheries biologist for the Yurok Tribe, holds up a Chinook salmon carcass found in one of the side channels being constructed along the Sacramento River near Anderson in Shasta County.


Doug Killam, senior environmental scientist with CDFW’s Northern Region, stands along the first of three side channels that was excavated and connected to the main stem of the Sacramento River in 2020.


Willow and cottonwood cuttings have been placed throughout the side channels construction site. They will ultimately provide a cooling canopy for salmon and steelhead and relief from the areas’ scorching summer heat.


Creating three meandering side channels off the Sacramento River near Anderson has involved heavy construction and earth-moving equipment over the past 12 months.


An oasis of slow-moving, meandering, cooling waters with deep pools and oxygenating riffles off the Sacramento River near Anderson will offer new spawning and rearing habitat for both salmon and steelhead.

An oasis of meandering waterways with deep pools, shallow gravel beds, protective log overhangs, oxygenating riffles and a cooling canopy of willows and cottonwood trees is being created for salmon and steelhead along the banks of the Sacramento River on CDFW-owned property near the city of Anderson in Shasta County.

Three new side channels off the Sacramento River have been carved from a dense, 40-acre riparian zone and floodplain that is being reconnected to the river adjacent to the Anderson River Park. The new habitat will serve as a protective nursery for juvenile salmon and steelhead off the main river while providing additional spawning habitat for adult fish.

“This was designed for rearing habitat,” explained Doug Killam, a senior environmental scientist with CDFW’s Northern Region, on a recent tour. “The moment we opened up the first channel and connected it to the river, adult salmon started showing up right away.”

The side channel project at Anderson is one of two currently under construction along the Sacramento River – the other taking place in downtown Redding. Both projects are being overseen by the U.S. Bureau of Reclamation as part of the Central Valley Project Improvement Act to mitigate impacts from lost habitat resulting from the construction of the Shasta Dam in 1945. Rocks and gravel being added to the side channels for fish habitat historically would have been delivered from upper reaches of the Sacramento River and all of the tributaries above Shasta Dam.

The Bureau of Reclamation contracted construction of the Anderson-area project out to the Yurok Tribe, whose reservation is situated along the lower 44 miles of the Klamath River. The tribe’s culture is rooted in salmon and fishing along the North Coast. Construction began a year ago and is nearly complete.

Few outside materials were brought in. Almost everything used to create ideal and idyllic fish habitat – stumps and snags, gravel and stones, willow and cottonwood cuttings – were acquired locally at the construction site, repurposed and recycled. The side channels themselves were dug out and designed based on historic waterways that used to exist.

“The Yurok Tribe has been fishing for time immemorial and being a fisherman myself, we know what salmon want,” said Luis Santana, fisheries biologist for the Yurok Tribe. “Everything we’re doing here is in the best interest of native fishes.”

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Media Contact:
Peter Tira, CDFW Communications, (916) 215-3858

CDFW Photos

Salton Sea, Riverside and Imperial Counties.


Surface roughening at Salton Sea.


Monitoring equipment.


Dust suppression at Salton Sea.


Fishery biologists Sharon Keeney of CDFW (r) and Shauna Bishop of Barrett's Biological Surveys look for desert pupfish.

Stretching between Southern California’s Imperial and Coachella valleys, the Salton Sea is what one might call a landmark of untraditional beauty. At 33 miles long and 5 miles wide, it’s the state’s largest inland lake, serving a crucial role as a stopover for migratory birds using the Pacific Flyway.

But the Salton Sea lacks the conventional, inviting atmosphere of other lakes on the West Coast. Its waters are rapidly evaporating, leaving another few thousand acres of dry and dusty lakebed (playa) each year. That loss of water increases the lake’s already-high levels of salinity, and it occasionally emits a pungent rotten egg odor that permeates the air. And – of particular concern to scientists – the evaporation decreases habitat for the wildlife that has historically thrived in and around this important ecosystem.

“Since its formation, the Salton Sea has been fed by irrigation runoff in the Imperial and Coachella valleys and inflow from rivers,” explained CDFW’s Salton Sea Program Manager Gail Sevrens. “But water transfers and related agreements and measures have contributed to a reduced volume of runoff, and as the water evaporates, the Sea has lowered in elevation. This has led to a shrinking, saltier Sea, and those increased areas of exposed dry lakebed can emit dust, which is of concern to local communities.”

Sevrens oversees CDFW’s participation in the Salton Sea Management Program (SSMP), which seeks to address those concerns, both for the benefit of fish and wildlife and the humans that live in the valley. The SSMP is an effort between CDFW and the California Department of Water Resources, under the direction of the California Natural Resources Agency. The partners seek to implement projects that will slow the damage and aid in recovery, primarily through the construction of approximately 30,000 acres of habitat and dust suppression projects around the Sea.

The program has several priorities:

• Making significant, visible progress in getting restoration and dust suppression projects accomplished as part of its 10-Year Plan;
• Creating a long-term plan;
• Building the team; and
• Strengthening local partnerships.

Many Californians are unfamiliar with how the current Salton Sea came to existence – it’s not an exaggeration to call this an “accidental lake.” Though large seas have formed and dried here throughout history due to natural flooding from the Colorado River, the Salton Sea in its current iteration was born in 1905 when the Colorado River breached an irrigation canal being constructed in the Imperial Valley. The escaping water slowly filled a dry lakebed nearly 300 feet below sea level. At first, developers imagined the Sea as a popular lakeside resort. But it was not to last, as without a continued, reliable source of water supply, the lake’s waters could only evaporate, reducing conditions for wildlife and nearby residents. In fact, due to agricultural runoff and evaporation, the water in the Salton Sea is approximately twice as salty as ocean water.

This fall, work began on the nearly 4,000-acre Species Conservation Habitat (SCH) project. That work will create a series of ponds at the southern end of the Sea that will include nesting and roosting islands and areas of varying water depths to serve as fish and bird habitat. At its healthiest, the Salton Sea was host to a half dozen species of fish, while 400 species of birds visited the lake while traversing the Pacific Flyway.

The SSMP projects provide dust suppression benefits. For example, temporary dust suppression measures have been taken on the south side of the Sea at the SCH site, where, through a process called surface roughening, approximately 700 acres of land were manipulated to create ridges and furrows that are perpendicular to the prevailing wind direction. Additional dust suppression and habitat restoration projects are in development for areas of exposed dry lakebed around the Salton Sea.

According to CDFW Environmental Scientist Samantha Przeklasa, the seemingly simple approach of rearranging the ground can make an enormous difference. “When the wind comes across the surface-roughening furrows, they slow the wind and catch particulate matter in the air. That matter gets caught in the little furrows, in the low spots.

(Watch this video tour of the Salton Sea with Environmental Scientist Samantha Przeklasa)

Though habitat work is just beginning, scientists are seeing the benefits for one species already. Przeklasa praises fellow CDFW Environmental Scientist Sharon Keeney for her work finding, relocating and ultimately saving desert pupfish. The only native fish species at the Salton Sea, the tiny pupfish are found in shoreline pools, agricultural drains and natural creeks. Though pupfish can survive low levels of dissolved oxygen, high salinity and high water temperatures, they won’t survive in ponds and ditches that go dry. That’s where Keeney’s work has truly made a difference.

“There are many irrigation drains across the entire Salton Sea, on the north and south. Sharon spends a lot of her time monitoring those drains to see where the pupfish are thriving, and then rescues them from small drains that may be about to completely dry up,” said Przeklasa. “From a small pond, we can get hundreds, if not thousands, of fish out of it.” The fish are relocated to nearby ponds that are fed by natural desert springs, or managed ponds. Desert pupfish have also been relocated to ponds at a local high school, UC Riverside’s Palm Desert campus, and the Living Desert Zoo and Gardens in Palm Desert. The latter has even named one of its newest desert pupfish refuge ponds after Keeney.

Ultimately it will be engineering and habitat construction that helps the pupfish and other species survive. The work being done brings joy to program manager Sevrens, who was first attracted to the unusual beauty of the Salton Sea through documentaries. Her affection for the lake grew even further while bird-watching and occasionally kayaking there.

“A lot needs to go on behind the scenes before you can actually do a project, and we are moving forward on multiple project tracks at a time,” she said. “It’s exciting to see the pieces coming together.”

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Media Contact:
Tim Daly, CDFW Communications, (916) 201-2958

CDFW Photos

The California Fish and Wildlife Journal concludes the 2020 Special Issue installments with the winter quarter’s Special Wildland Fire Issue. With this year’s unprecedented fire season, and California’s fire-adapted natural communities taking center stage in land management discussions throughout the State and beyond, this issue is especially poignant as we reflect on this past year and contemplate the incoming new year.

Unlike previous Special Issues, this issue is divided into three sections: Vegetation Treatment and Policy, Fire Impacts on Plants, and Fire Impacts on Wildlife and Water. Each section highlights a piece of the wildfire and landscape management ‘puzzle’ through an examination of fire and its impacts on California’s fire-adapted ecological landscape.

One of these unique communities, the Pine Hill Ecological Reserve in El Dorado County, is home to almost 750 plant species, some of which can only be found at Pine Hill due to its unique soil composition. Researchers from CDFW, the California Native Plant Society and Sacramento City College investigate the impacts of different fuel-reduction methods on Pine Hill Ceanothus in “Effects of a firebreak on plants and wildlife at Pine Hill, a biodiversity hotspot, El Dorado County, California” (PDF). The article examines the effects of hand clearing and pile burning on chaparral species within the Wildland Urban Interface and the secondary impacts on wildlife. The study also includes the exciting discovery of new seedlings of Pine Hill Flannelbush, the rarest and most endangered plant in El Dorado county, and a fire-obligate germinator!

Plants that depend on fire to propagate aren’t the only plant communities impacted by the long-term fire suppression practiced in the western United States. New and updated technology is helping landscape managers and scientists study and assess the pre- and post-fire impacts to landscapes using remote sensing and modeling techniques. This type of data collection and analysis helps inform scientists and policy makers on landscape and watershed-level scales and helps focus efforts to manage habitats and sensitive plant communities before and after wildfires. One such effort is presented by Sonoma County scientists in “Sonoma County Complex Fires of 2017: Remote sensing data and modeling to support ecosystem and community resiliency” (PDF). With the help of NASA and other experts the team evaluates the impacts of the 2017 fires to woody vegetation within areas that burned during wind-driven and non-wind driven events to evaluate canopy condition. Using lidar data, the team identifies important predictors for post-fire woody canopy condition, which highlights the importance of high-resolution airborne mapping technology for informing management decisions.

Management decisions include when and how to monitor pre- and post-fire events, and the CSU Monterey Bay’s study “Analysis of the impacts of the Soberanes Wildlife on stream ecosystems” (PDF) highlights the need for monitoring wildfire’s impacts on coastal streams and benthic macroinvertebrate responses to fire events. This monitoring is especially important because macroinvertebrates are the foundation for in-stream salmon and steelhead foodwebs, and the ability of these microscopic organisms to recover from wildfire also impacts the recovery of these keystone species in California’s rivers and streams.

This quarter’s Special Wildlife Fire Issue also includes examinations of impacts and responses of Roosevelt Elk forage in Humboldt County, an essay on the California Vegetation Treatment Program, amphibian responses to wildfire and other topics that span California’s rich ecological diversity.

The California Fish and Wildlife scientific journal has published high-quality, peer-reviewed science that contributes to the understanding and conservation of California’s wildlife for more than 100 years. We look forward to the continued contributions in the next decade to come.

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Media Contact:
Kirsten Macintyre, CDFW Communications, (916) 804-1714

CDFW biologists and hatchery staff overcame several obstacles for a successful 2020 kokanee salmon egg collection effort on the Little Truckee River.


Kokanee salmon eggs are collected and fertilized streamside, as shown in this 2019 photo, before being taken to a CDFW hatchery for incubation.


A temporary weir is set up along the Little Truckee River to block, catch and spawn kokanee salmon that have migrated up from Stampede Reservoir as shown in this 2019 photo. Among other challenges in 2020, CDFW staff had to conduct the annual kokanee spawn without the help of volunteers due to COVID-19-related precautions.

In spite of challenges presented by wildfires, forest closures, unhealthy air quality and the COVID-19 pandemic, CDFW staff from the American River Trout Hatchery and Fisheries Branch nonetheless conducted four successful kokanee salmon egg collections on the Little Truckee River this fall.

Slightly more than 1.3 million eggs were collected from kokanee salmon migrating from Stampede Reservoir in Nevada County into the Little Truckee River to spawn. Stampede Reservoir’s kokanee salmon serve as CDFW’s broodstock for the popular State fishery.

CDFW typically relies on volunteers from the public and angling groups to help with the annual egg collection effort – but that extra manpower was unavailable this year due to COVID-19 precautions.

“This year was unique to say the least, but this was a high priority for us,” said Jason Julienne, senior environmental scientist supervisor for CDFW’s North Central Region hatcheries. “Many of the waters that support the kokanee fishery are not self-sustaining, and depend on annual releases to provide ample opportunity for anglers.”

Due to COVID-19 concerns, this year’s egg collection involved less staff than normal, which slowed the process a bit. Typically, the team can collect all the eggs needed to support the program in two to three days. This year, it took four days, and required extensive coordination with the U.S. Forest Service in order to get special access to closed areas of the Tahoe National Forest.

“Luckily, everything came together on time and we were able to get it done,” Julienne said. “We had 12 to 15 staff participating in each of the four egg collections, as well as two staffers who remained onsite for five weeks to maintain the fish barrier weir and monitor salmon numbers coming up the river.”

The collected eggs are now being incubated at CDFW’s San Joaquin Hatchery and American River Trout Hatchery. Once the fry reach about three inches in size, they will be stocked to support recreational fishing at 15 lakes and reservoirs throughout the state. About 850,000 kokanee fry are released annually.

Kokanee salmon (Oncorhynchus nerka) are the landlocked version of Sockeye salmon native to Alaska and the Pacific Northwest. Instead of migrating to the ocean, adult kokanee inhabit large lakes and impoundments before returning to their natal streams or using gravel shorelines to spawn. Like all Pacific salmon, kokanee die after spawning, their whole life cycle spanning two to four years.

Although they only average about 12 inches in size as adults, kokanee salmon are an exceptionally popular sport fish noted for their excellent table fare. As the kokanee fishery has thrived, bag and possession limits have been increased at several lakes and reservoirs in recent years, including at Lake Pardee in Amador County, New Bullard’s Bar Reservoir in Yuba County and Trinity Lake in Trinity County.

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Media Contact:
Peter Tira, CDFW Communications, (916) 215-3858

CDFW Photos