Science Spotlight

An Op-Ed by Charlton H. Bonham, Director of the Department of Fish and Wildlife

Beavers are having a well-deserved moment in the discussion around climate solutions.

Healthy beaver populations improve their environment in so many ways – from reducing wildfire risks, to making water conditions more hospitable for our native salmon and trout.

In fact, humans have so admired the skilled work of beavers they have spent millions of dollars trying to replicate the benefits they create. As managers of the state’s natural resources, the California Department of Fish and Wildlife (CDFW) is embracing the opportunity to elevate beaver restoration as part of a larger effort to help mitigate the impacts of wildfires, climate change and drought. Thanks to Governor Gavin Newsom’s leadership and the State Legislature, funding for beaver restoration is now part of our playbook, with funds approved in this year’s budget.

The program funds dedicated scientists who, once hired by CDFW, will begin working on projects that help the environment by bringing beavers back to California rivers where they once thrived.

Beaver dams raise groundwater levels and slow water flow. Slowing down the flow allows water to pool and seep, creating riparian wetlands that support plant, wildlife and habitat growth. Another benefit of beaver dams is the rejuvenation of river habitat for salmon and aquatic insects. The dams also improve water quality because they capture sediment, resulting in clearer water downstream.

Additionally, beaver dams help keep groundwater tables high which can help mitigate drought impacts by keeping vegetation green. This effect can also help fires burn less intensely in riparian areas, which, in the long run, can aid streams and habitats in recovering from fires more quickly. These positive ecosystem benefits are especially true in areas where there are intermittent streams or where streams can disconnect. Once beavers build dams in those areas, the habitat tends to hold water more effectively and allows it to percolate into soils.

Unfortunately, beavers were eliminated from much of their range by the late 1800s due to unregulated trapping and habitat loss. Environmental scientists have tried to duplicate the effectiveness of beaver dams utilizing human-engineered structures called beaver dam analogues. Through this, we have learned that human-created beaver dams can achieve similar carbon sequestration and habitat benefits to that of real beaver dams, but at a much higher cost. Nothing’s better than the real thing, and that means bringing beavers back to their historic habitat and teaching Californians how to coexist with the scientifically named Castor canadensis.

California’s next step is to expand partnerships with California native tribes, non-governmental organizations, private landowners, state and federal agencies, and restoration practitioners to lay the groundwork for implementing beaver restoration projects. The new funding will help develop a framework for these beaver relocation efforts. CDFW and its partners are looking at the feasibility of taking beavers from areas where they are causing conflict and relocating them to areas where they would have ecosystem benefits.

CDFW’s new beaver restoration program allows California to advance on all these fronts -- we’re continuing collaboration with partners and stakeholders, continuing to work on restoration sites where we’ve funded beaver dam analogues and continuing to lay the groundwork for re-introduction of beavers in areas where it may have ecosystem benefits. Scientists are confident that beaver restoration has the potential to be a nature-based strategy that can aid in reducing wildfire risk, mitigating drought and combating climate change. It’s another piece in the puzzle as CDFW works to implement solutions to some of our greatest environmental concerns.

CDFW Scientific Aid Stew Sloan measures pool depth at Pacific Creek.


A Lahontan cutthroat trout swims within Milk Ranch Creek.


Environmental Scientist Allison Scott records data on the banks of Pacific Creek.


A handheld multiparameter instrument displays several creek measurements at once.


CDFW's Allison Scott and Aaron Sturtevant measure pool depth within Milk Ranch Creek.

As holiday visitors vacated the Stanislaus National Forest at the conclusion of the long Fourth of July weekend, the California Department of Fish and Wildlife’s (CDFW) Heritage and Wild Trout Program moved in.

Four team members from the statewide program – Environmental Scientist Allison Scott, scientific aids Aaron Sturtevant and Stew Sloan, along with new program leader Farhat Bajjaliya – set up camp within the border region of Alpine and Stanislaus counties in the northern reaches of the Eastern Sierra.

The team spent the better part of three days rock-hopping, climbing and carefully picking their way upstream along three small creeks within the high elevations of the Carson-Iceberg Wilderness searching for and counting wild Lahontan cutthroat trout (Oncorhynchus clarkii henshawi). The goal was to see how the fish and their habitat were faring in a third summer of California drought. Along the way, the team paused regularly to record water temperatures, creek flows and dissolved oxygen levels and take pool depth measurements. They took photos, referenced waypoints on their Garmin unit and thoroughly explored any smaller tributaries feeding into the main creeks, some just a couple inches deep at points.

“One of the things we really key in on is pool habitat,” explained Bajjaliya. “When drought conditions get really bad, that’s where the fish will go and seek refuge so we want to keep an eye on that.”

The three small creeks surveyed – Marshall Canyon Creek, Pacific Creek and Milk Ranch Creek – share similar characteristics.

Their lower reaches are occupied by introduced non-native brook trout (Salvelinus fontinalis). Various impenetrable natural barriers such as steep, cascading waterfalls or sheer granite rock cliffs prevent the brookies from accessing the higher-elevation stretches home to the Lahontan cutthroats. The Lahontan cutthroat trout themselves are not necessarily native either as these particular creeks are situated outside of their historic watersheds. The fish were put there decades ago by biologists to serve as refuge populations just in case the fish, a federally listed threatened species, disappeared elsewhere within their native range.

CDFW’s trout team hiked almost 10 miles each day carrying a mix of high-tech and low-tech equipment. On one end of the technology spectrum was the YSI handheld digital “multiparameter instrument,” which simultaneously measures pH levels, dissolved oxygen, temperature and the ability of the water to absorb and break down waste products such as contaminants and dead plants and animals. On the other end of the spectrum was the collapsible stadia rod. Resembling a folding yardstick, it’s used to measure pool depth and creek width. No electrofishing gear was packed in. Lahontan cutthroat trout were counted and sized only through visual observations – and often fleeting observations at that.

The scientific work is formally known as drought stressor monitoring and it makes up a significant portion of the Heritage and Wild Trout Program’s field season, which stretches from May to November and occurs across the state wherever sensitive native trout populations exist. The program’s environmental scientists and part-time scientific aids typically spend eight consecutive days in the field followed by six consecutive days off work.

The value of this type of hands-on, eyes-on field work was driven home during California’s last drought. Drought monitoring surveys similar to the ones within the Carson-Iceberg Wilderness led to the dramatic rescues of McCloud River redband trout (Oncorhynchus mykiss stonei) and California golden trout (Oncorhynchus mykiss aguabonita) – the official state freshwater fish.

Drought monitoring in the summer of 2014 revealed deteriorating habitat conditions near Mount Shasta and prompted the rescue of McCloud River redband trout (Video) from four creeks among the headwater tributaries of the McCloud River. With no suitable options available to relocate the fish on the landscape, CDFW took the unusual step of bringing the wild trout – a designated state species of special concern – into its Mount Shasta Trout Hatchery until they could be returned to their native habitat when environmental conditions improved.by the fall of 2016.

While at the hatchery, CDFW was able to successfully spawn the redbands. The Mount Shasta Trout Hatchery has maintained a broodstock population ever since and stocks their offspring into local waters for recreational fishing to expose more trout anglers to this colorful and rare native species.

Drought stressor monitoring led to the September 2016 rescue of California golden trout from Volcanic Creek, situated high in the southern Sierra Nevada range at 9,000 feet within the Inyo National Forest. Fifty-two fish – a representative sample that could repopulate Volcanic Creek and save the genetically pure strain of goldens if conditions worsened – were collected and taken to the American River Trout Hatchery near Sacramento to wait out the drought before being returned to their native habitat in 2017 (Video) when environmental conditions improved.

The Lahontan cutthroat trout is in a far more precarious situation than either the McCloud River redband trout or the California golden trout. Lahontan cutthroat trout were listed as an endangered species by the federal government in 1970 – three years before the modern, federal Endangered Species Act was signed into law in 1973 by President Richard Nixon. The fish have languished as a federally listed species ever since. Their status was downgraded to “threatened” in 1975 but only to allow for more aggressive management and recovery efforts and to allow recreational fishing.

Once occupying a vast range east of the Sierra Nevada, Lahontan cutthroat trout have disappeared from nearly 95 percent of their native habitat in California, which includes Lake Tahoe, the Carson, Truckee, and Walker river basins, as a result of habitat degradation and competition from non-native trout.

The 50th anniversary of the species’ federal listing in 2020 was something of an ignominious milestone. Several state and federal agencies – including the U.S. Fish and Wildlife Service, the USDA Forest Service, CDFW and the Nevada Department of Wildlife – have joined forces recently to redouble efforts and accelerate Lahontan cutthroat trout recovery.

All of which helps explain why keeping close tabs on the few remaining wild, self-sustaining, genetically pure populations of Lahontan cutthroat trout left in California is a priority for CDFW and the Heritage and Wild Trout Program specifically.

Back at the Carson-Iceberg Wilderness within the Stanislaus National Forest in July, the day’s drought monitoring work ends when 200 Lahontan cutthroat trout have been tallied or the habitat simply disappears back into the ground at the headwaters source or becomes otherwise impenetrable by either fish or human.

At all three creeks, the trout habitat ran out before 200 fish were counted. The team observed 153 Lahontan cutthroat trout at Milk Ranch Creek, 33 in Marshall Canyon Creek and 23 at Pacific Creek. The team seemed satisfied with what it saw.

The habitat was holding up well for early summer conditions and enough Lahontan cutthroat trout – mostly 6 inches and shorter in length – were observed in the wildflower-laden, meadow sections of each creek’s upper reaches. The numbers of fish were reasonably consistent with drought monitoring conducted in 2020 and 2021. The numbers of fish observed in Marshall Canyon Creek and Milk Ranch Creek exceeded the numbers counted the previous two years.

No fish were spotted in the steeper, faster, rockier, lower portions of the creeks. No emergency rescue missions were discussed.

“There really is no reason for them to leave the meadows,” explained CDFW’s Scott. “That’s where the best habitat is and there are not so many fish that some are forced to move out.”

Media Contacts:
Farhat Bajjaliya, CDFW Heritage and Wild Trout Program, (916) 215-5330
Peter Tira, CDFW Communications, (916) 215-3858

Austin Reeder, region 1 specialist


David Mollel, region 2 specialist


Megan O’Connor, region 2 specialist


Megan Senour, region 3 specialist


George Harse, region 4 specialist


Chris DeTar, region 4 specialist


Jessica West, region 5 specialist


Rebecca Barboza, region 5 specialist


Kevin Howells, region 6 specialist


Dan Taylor, region 6 specialist


Ryan Leahy, statewide specialist

It’s not all that unusual for wild animals to end up in places where they shouldn’t be — you’ve probably seen video on the nightly news, read about it in the newspaper or maybe heard a rumor spread on your neighborhood social media group. Sometimes it’s a bear in a backyard or a young mountain lion near a school. Other times, it’s an aggressive turkey chasing a delivery driver or a coyote that steals food out of your outdoor pet dish. These are examples of human-wildlife conflict incidents, for which the public often turns to CDFW for guidance and solutions.

CDFW is the lead state agency responsible for responding to human-wildlife conflict and depredation (wildlife damage to private property) incidents. The types of human-wildlife conflict that can occur in California are as diverse as the people and wildlife that live here. Public perception, understanding and tolerance of wildlife can vary widely — leading to unique challenges for CDFW as a public trust agency. To meet these challenges, CDFW has recruited a team of wildlife conflict specialists that are skilled and equipped to serve local communities, agency partners and the diverse publics that co-exist with wild animals statewide.

On April 29, 2022, CDFW’s Human-Wildlife Conflict Program — part of the department’s Wildlife Health Lab (WHL) — graduated its first ever training cohort from its new Wildlife Conflict Training Academy. This training academy, similar to CDFW’s Warden Academy, provides staff with the tools, knowledge and resources necessary for safe, effective wildlife incident response. Coursework covered state codes and regulations, CDFW policy, wildlife capture and handling, public outreach, media training and wildlife damage management techniques focused on effective nonlethal tools. Coursework included cross-training on Wildlife Watch, a “train-the-trainer” program model designed to empower and inspire local communities with respect and stewardship for wildlife, and how to safely coexist with wildlife.

“I am so proud of our statewide Regional Conflict Specialists Team,” said Vicky Monroe, CDFW Conflict Programs Coordinator. “We’ve created a robust framework and a clear vision to support them and this important work.”

Monroe added that in addition to developing the training academy, a human-wildlife conflict “toolkit” and a Wildlife Damage Management speaker series, CDFW has provided a platform for the new team to receive technical assistance and training, as well as share experiences across CDFW’s regions.

“Our statewide team have a difficult job, but we are committed to helping transform conflicts with wildlife statewide,” she said.

The 11 CDFW wildlife conflict specialists completed 20 hours of course training and will work closely with other CDFW biologists and wildlife officers statewide, as well as CDFW’s Natural Resource Volunteer Program (NRVP) volunteers. Wildlife incident tracking and response guidance are all part of this effort to increase capacity and improve operational efficiencies.

Under this new robust framework, a minimum of two wildlife conflict specialists in each CDFW region provide dedicated support responding to human-wildlife conflict incidents reported to CDFW. Reporting parties range from members of the public to agency partners, local community leaders and law enforcement. Reports might come via the statewide online Wildlife Incident Reporting (WIR) System, by phone, email or in person. The conflict specialists work to help resolve wildlife incidents specific to the circumstances, which can vary. For example, a report about a “nuisance” raccoon or fox sighting might best be addressed with technical assistance by email or phone. A report about a mountain lion depredation could require a field response and technical assistance. A report about an orphaned bear cub could require a field response and close coordination with the WHL and regional staff.

The factors that contribute to human-wildlife conflict may vary, but one thing will not: CDFW’s new statewide Regional Conflict Specialists Team is ready, and on the frontline helping local communities, property owners and the public learn to safely coexist with wildlife!

Windmill fed water trough on American Unit with view of the Carrizo Plain.


Former windmill site on American Unit, now provides water with electric pump. Popular elk hangout.


Fossil canyon guzzler/tank system installed for Eagle Scout Project.


Rain collection roof in Fossil canyon. Installed by Boy Scouts.

Wildlife at the 38,900-acre Carrizo Plains Ecological Reserve in San Luis Obispo County have a little better access to water than what the land naturally offers. There are about 30 water troughs spread throughout the reserve—all fed by water storage tanks and guzzlers via miles of underground piping.

The water infrastructure hails from the heyday of cattle grazing in the 1970s. CDFW inherited the aging system when it purchased the land in the early 1990s. The system has since been converted for wildlife use by CDFW and is maintained by staff and volunteers.

“It’s such a good combination of the past, present and future,” said CDFW Habitat Specialist Joe Lambirth. “Using windmills and troughs from the past, we tweaked the system and made it better through improvements like installing solar pumps and piping that lasts longer. I’m sure in 10 or 15 years someone will find a way to make our system better. I’m kind of counting on it.”

Around 2005, CDFW began converting the cattle troughs for wildlife use. Staff came across a design for a trough that was being used by a local rancher. The troughs were eight feet long, made of concrete, and low to the ground—a durable design that would allow a variety of wildlife to access water from them. CDFW staff worked with the trough manufacturer to increase the length to 12 feet and added a cover to protect the float assembly.

The troughs are used by a variety of wildlife at the reserve including deer, elk, antelope, kit foxes, mountain lions, bears, reptiles, bats and many bird species.

When choosing trough locations, staff consider the needs of the wide variety of species that will benefit from their use.

“We try to find the right mix of open area and cover. Some wildlife might need to shoot out from a bush and get back quickly. A golden eagle might look for a perch that it can use to swoop down from. We try to put troughs near wildlife corridors like streams or canyons so the animals’ natural migration will lead them through the area,” said Lambirth.

Most of the troughs are fed by 5,000-gallon water storage tanks. A 5,000-gallon tank will typically feed a wildlife trough for at least two months, even in the heat of summer.

Visit CDFW’s Carrizo Plains Ecological Reserve web page for more information.

CDFW staff with tanker truck used to transport smolts


The Salty Lady sportfishing boat hosted Richmond youth


Smolts being released into Richmond Harbor






Fall-run Chinook salmon smolt

Moments after the sun set on Richmond Harbor’s Brickyard Cove on June 19, CDFW and its partners released approximately 200,000 hatchery raised juvenile fall-run Chinook salmon (known as smolts) into the bay.

The release was part of a larger effort to truck approximately 19.7 million fall-run Chinook salmon to locations in the San Francisco Bay, San Pablo Bay and lower portions of the Sacramento-San Joaquin Delta. CDFW has two more smolt releases planned for the week of June 20. Since beginning the effort in mid-April, staff have completed three to six releases per week.

Sunday night’s release was a collaboration with the City of Richmond, Golden State Salmon Association and Richmond Police Athletic League. The team invited a group of young people from Richmond to watch the release from a 56-foot sportfishing boat called The Salty Lady, the use of which was donated for the event to offer youth a glimpse into fishery operations.

“These kids definitely got a unique opportunity and a front row seat to watch this release,” said Senior Environmental Scientist Jason Julienne, supervisor over CDFW’s North Central Region hatcheries. “I hope it gets them interested and excited for fish and fishing, with the hopes of catching one of these fish when they return as adults in a few years.”

The goal of the releases is to improve survival of the salmon smolts by helping them bypass 50 to100 miles of hazardous river conditions caused by three consecutive years of drought in the Central Valley. CDFW fisheries biologists tracked flows and water temperatures in the fish's usual migration corridors and recognized that survival would be a challenge without intervention.

“We want to help ensure some of these fish survive to contribute to commercial and recreations fisheries, as well as hatchery and natural area production in the coming years,” said Julienne.

The smolts, raised at CDFW’s Feather River Fish Hatchery in Oroville, were eight to 10 months old when released. At that age, the smolts are developmentally ready to handle the salinity of bay waters. The Brickyard Cove location in Richmond was chosen because of its favorable tides and proximity to deep waters.

“We try to use outgoing tidal movements and the cover of darkness to help get these fish oriented in the right direction toward the Pacific Ocean, and reduce predation,” said Julienne.

All fish from yesterday’s release were marked and implanted with coded wire tags so CDFW can track their returns and determine how they contribute to fisheries and production in coming years.

For more information read CDFW’s news release on the trucking operation.