Science Spotlight

Upper Independence Creek provides vital spawning habitat for the Lahontan cutthroat trout in Independence Lake.


State and federal agencies, joined by conservation groups such as Trout Unlimited, have worked for decades to safeguard the wild Lahontan cutthroat trout population at Independence Lake, the only self-sustaining lake population of the native species left in California. Trout Unlimited’s Brandon Reeder shows off a hefty Lahontan cutthroat captured at a temporary weir to count spawning fish.


Lahontan cutthroat trout spawn in upper Independence Creek, where biologists have worked for years to remove non-native brook trout.


Each spring, biologists and volunteers set up a weir at upper Independence Creek to trap spawning Lahontan cutthroat trout and assess the population.

The news out of UC Davis last spring knocked California native fish biologists for a loop.

Genetic testing of native Lahontan cutthroat trout from Independence Lake in the Tahoe National Forest near Truckee found evidence of hybridization with non-native rainbow trout.

To understand the magnitude of that news you have to understand that Independence Lake is the only lake in California – and just one of two lakes in the world – to support a self-sustaining lake population of Lahontan cutthroat trout, a trout native to the eastern Sierra range and the Lahontan basin of Nevada.

And you have to understand that for decades, California Department of Fish and Wildlife (CDFW) biologists – joined by colleagues at the U.S. Geological Survey, U.S. Forest Service, the U.S. Fish and Wildlife Service and conservation groups including The Nature Conservancy and Trout Unlimited – have worked to safeguard these fish, enhance their habitat, and reduce competition from non-native brook trout, brown trout and Kokanee salmon introduced over the years into Independence Lake.

Lahontan cutthroat trout are listed as a threatened species under the federal Endangered Species Act. Their original listing in 1970 predates the modern act itself, which was passed in 1973.

Each fall, as part of species recovery efforts, biologists from CDFW and partner organizations electrofish upper Independence Creek, which feeds into Independence Lake, to remove brook trout from the creek that the Lahontan cutthroat trout depend on to spawn. Also in the fall, biologists set up a weir on the creek to block any of the lake’s resident brown and brook trout from moving up the creek to spawn. Non-native trout staging for a fall spawning run at the mouth of Independence Creek are stunned to the surface through electrofishing and removed from the lake.

“For the past 20 years at Independence Lake, we’ve been trying to give the cutthroat a helping hand by removing the non-native trout. It’s not a done deal but we’ve been pretty successful at reducing brown and brook trout down to very low numbers,” explained Dave Lentz, CDFW’s native trout conservation coordinator. “Lahontan cutthroat trout did not evolve with brook trout or brown trout on the landscape and they have been out-competed and displaced by these and other non-native species throughout much of the cutthroat’s historic range.”

Each spring, when the Lahontan cutthroat trout move up to spawn in upper Independence Creek, biologists and volunteers return with their weir to capture and count the numbers of spawning fish to assess population trends.

This spring, however, the spawning surveys will take on a new sense of urgency. After last year’s disheartening news from genetics experts, CDFW staff and partners captured some 170 Lahontan cutthroat trout from Independence Lake, took genetic samples and outfitted each trout with an identifying Passive Integrated Transponder (PIT) tag before releasing the fish back to the lake.

The tissue samples were sent to two labs for genetic testing. The results indicate that some 20 percent of the cutthroats captured and tagged last year show evidence of hybridization with rainbow trout. Biologists are now discussing plans and options for the spring spawn. Cutthroat trout returning to upper Independence Creek will be trapped and scanned with a PIT reader. Unmarked fish will be given a PIT tag, genetic samples will be taken for later testing, and the fish will be returned to the lake.

“We want to prevent further spawning by hybridized trout. We’re using some emerging science and the latest genetics information to manage this fishery,” said Lentz. “The situation is dire for Independence Lake cutthroat trout but we hope to improve their status by taking these measures.”

There are no known populations of rainbow trout within Independence Lake that could account for the hybridization but they are present in lower portions of Independence Creek below the lake. The outlet of the lake, however, is controlled by a dam that does not allow for fish passage into the lake. CDFW and partners will continue to investigate how rainbow trout gained access to the lake. It is thought that the rainbow invasion and hybridization are recent events, likely in the last 10 years.

The effort to remove hybridized cutthroat trout from Independence Lake takes place as state and federal officials in California, Nevada and Oregon step up collaborative efforts to increase Lahontan cutthroat trout awareness and recovery across their native range. Among those efforts:

• A genetic assessment of Lahontan cutthroat trout across their historic range has been underway for the past several years. That process resulted in the UC Davis findings of hybridization within the Independence Lake cutthroat population.
• In May 2019, the U.S. Fish and Wildlife Service released a document that updates recovery goals and objectives from its 1995 Lahontan cutthroat trout recovery plan using current science and a new conservation framework for species recovery.
• In October 2019, the U.S. Fish and Wildlife Service released 5,000 Pilot Peak strain Lahontan cutthroat trout back into Lake Tahoe, returning the native, fast-growing strain to Lake Tahoe for the first time in nearly 90 years.
• This coming May, state and federal fisheries biologists are scheduled to begin planning Lahontan cutthroat trout recovery and outreach efforts within the Carson River drainage.
• CDFW’s Hot Creek Trout Hatchery in the eastern Sierra is preparing facilities to establish a new rearing program for the Walker River strain of Lahontan cutthroat trout native to the Walker River drainage and Nevada’s Walker Lake.

CDFW Photo. Top Photo: A windy day at Independence Lake in the Tahoe National Forest.

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

Some of the 160 people who assisted Fish and Wildlife with it's March 1 desert bighorn sheep survey. CDFW photo.


Charles and Nicole Lozano of Chino Hills using binoculars and a spotting scope to locate sheep. CDFW photo.


The San Gabriel Mountains, north of Ontario, where the sheep survey took place. CDFW photo.

The San Gabriel Mountains, north of Ontario, are a spectacular location for those who enjoy steep hikes and beautiful scenery. But one Sunday each year, those mountains are visited by people with a more specific agenda. They’re there to assist environmental scientists from the California Department of Fish and Wildlife in determining the number of desert bighorn sheep living there.

On March 1, 2020, about 160 volunteers gathered near the rugged terrain for the annual sheep count. Their goal was to use spotting scopes and binoculars to locate sheep, and determine and record their gender and approximate age. The volunteers attended a mandatory training session the night before in which CDFW staff briefed them on the purpose, counting techniques and best gear and supplies to bring for what can be a long day in tough elements. And as it turned out, March 1 was the one day in a stretch of about 20 that included a forecast of rain, and the forecasters nailed it. Between the fluctuating poor conditions – including a steady rain, low clouds, strong winds and even hail – nearly every volunteer struck out on being able to locate any sheep.

Fortunately, the annual count also includes an aerial survey the day before the boots-on-the-ground effort, and the weather was cooperative on Feb. 29. Eight CDFW employees took turns that Saturday flying in a Bell 407 helicopter over the locations where they’d likely find the sheep groups. Flights were limited to 2.5 hours before refueling was necessary. The crew of three on each flight was responsible for taking notes and guiding the pilot, using a handheld GPS to drop a waypoint at each observed sheep location, and capturing the animals with camera gear. The doors of the aircraft were removed to improve visibility for the spotters.

CDFW Senior Wildlife Biologist and survey coordinator Jeff Villepique said a key element of the effort is determining the health of the younger animals.

“One of the things we look at is how many lambs from last year have survived to this year,” said Villepique. “We did get some decent numbers that will help us determine the recruitment ratio and give an indication that the population is growing and doing well.”

When CDFW first started conducting these counts in 1979, the desert bighorn sheep in the San Gabriels numbered about 740. That dropped to fewer than 200 in the late ‘90s, and currently the population is back up to about 400.  Villepique said the numbers rise and fall based on food availability, habitat loss, weather patterns and the history of wildfires.

One group that enthusiastically supports the survey is the Society for the Conservation of Bighorn Sheep. Volunteer Debbie Miller Marschke has joined the effort multiple times, and despite the lousy weather conditions, was happy to be out in the mountains once again.

“When you get out in the environment and you’re with positive people, it’s not a wasted day, it’s a memorable day,” Miller Marschke said, smiling as she braved the downpour. “If I stayed home, I wouldn’t remember what I did a month later. I’m going to remember this day all year long.”

Environmental Scientist Laura Cockrell records the weight of a wild turkey at Little Dry Creek prior to banding.


Wild turkeys banded in 2019 and 2020 are given one traditional, butt-end band on one leg and one rivet band on the other.


Environmental Scientist Laura Cockrell shows off the supply of butt-end bands prior to banding.

Turkey hunters in parts of Butte and Glenn counties who are skilled and lucky enough to bag a tom this spring may be in for a pleasant surprise: Their bird may be sporting some jewelry – a band on each leg.

Since early February, CDFW biologists at the Upper Butte Basin Wildlife Area – supported by the National Wild Turkey Federation (NWTF) – have been busy trapping and double-banding wild turkeys at the wildlife area’s Howard Slough and Little Dry Creek units. So far this year, some 45 turkeys have been banded, which include toms, hens and young males known as “jakes.”

The staff and volunteers have just about a month and a half to trap and band all the wild turkeys they can between the close of the waterfowl hunting season and the start of the spring wild turkey season in mid-March. It’s part of an innovative research effort aimed at better understanding the characteristics, growth rates, habitat use, range and abundance of the growing population of wild turkeys using the wildlife area.

Bird bands long have been an important research tool for biologists and considered a prize among many hunters who are allowed to keep them after reporting the band information. The Upper Butte Basin turkey banding project is the only one of its kind in the state, making those turkey bands a rare commodity and a valuable potential data source.

In addition to the banding, the turkeys are weighed, sexed and measured at various points before being released.

The wild turkey study began at the wildlife area in 2015 along with the launch of limited spring wild turkey hunts there. NWTF helped secure grant funding to start the hunt program and initiate the research effort. The funds came from the sale of upland game bird hunting validations and stamps required of upland game bird hunters.

“We thought it would be great to start getting an abundance estimate for the turkeys that we do have out here to make sure that we weren’t harming the population through the hunt program and also to see how much hunter opportunity we could potentially utilize,” said Kevin Vella, NWTF’s district biologist for California, Nevada, Oregon and Washington.

The spring wild turkey hunt program has been so successful and popular over its short history funding for the program and its research component will continue under CDFW’s general budget moving forward.

“I think Howard Slough especially offers some of the best turkey hunting I’ve seen anywhere,” said Upper Butte Basin Wildlife Area Manager Tim Hermansen. “Certainly, youth hunters have an excellent opportunity out here.”

Spring turkey hunts at both the Howard Slough and Little Dry Creek units are limited to lottery drawings through CDFW’s website in order to ensure an uncrowded, high-quality hunting experience. The hunter quota and the turkey harvest both have grown over the years along with the local turkey population. Hunter success ranged from 30 to 60 percent during the 2019 spring season but reached 100 percent for the youth hunt at Howard Slough in 2018.

Back to those double-banded birds.

Although 101 turkeys were banded at the wildlife area between 2015 and 2019, only three banded turkeys have been reported by hunters. That leads biologists to believe most of the turkeys have been prying off the traditional, “butt-end” bird bands, which have two edges that butt evenly together when clamped on.

The NWTF has since supplied Upper Butte Basin with rivet bands that are made of a harder metal and riveted closed when attached. The turkeys banded in 2019 and 2020 now receive a butt-end bird band on one leg and a rivet band on the other. Any of those harvested birds wearing a single rivet band will confirm suspicions that the birds have been prying off the butt-end bands.

“That’s the downside of doing any kind of novel research,” explained Laura Cockrell, a CDFW environmental scientist based at the Upper Butte Basin. “You only have your own mistakes to learn from.”

CDFW Photos. Top Photo: Upper Butte Basin Wildlife Area Manager Tim Hermansen releases a wild turkey after banding as Fish and Wildlife Technician Derek Schiewek and Seasonal Aid John Davis look on.

Media Contact:
Peter Tira, CDFW Communications, (916) 322-8908

Logan Weyand, left, a veterinary student form Washington State University, and Drew Trausch, a scientific aid with CDFW’s Big Game Program, help capture and collar a cow Roosevelt elk in Humboldt County this past fall. CDFW photo by Shwn Fresz.


CDFW crews work quickly to tag and collar a tranquilized cow elk in Humboldt County. CDFW photo by George Harse.


Sporting ear tags and a GPS tracking collar, a cow Roosevelt elk returns to heavy timber after being sedated. CDFW photo by Andrew Trausch.


Ear tags provide biologists with visual identification of Roosevelt elk study animals while GPS tracking collars can provide years worth of detailed date on movement and habitat preferences. CDFW photo by George Harse.

State biologists are now learning a great deal about California’s largest land mammal.

Roosevelt elk are one of three subspecies of elk native to California, joining the tule elk (the smallest of the three) and the Rocky Mountain elk. While a bull Rocky Mountain elk will have larger and more impressive antlers, the Roosevelt elk bests it in body mass. A bull Rocky Mountain elk can reach 700 pounds while a bull Roosevelt can exceed 1,000 pounds.

Despite their massive size and majestic appearance, Roosevelt elk have proved an elusive research subject because of the dense forests they inhabit. Aerial surveying and trapping – standard tools for counting and collaring deer, elk and bighorn sheep in more open parts of the state – can be challenging for Roosevelt elk moving in and out of heavy coastal timber.

While deer often can be darted and tranquilized using a biologist’s truck as cover, Roosevelt elk are more wary and vehicle-shy, often requiring a lengthy stalk and serious hunting skills to get within the 50-yard effective range of a dart gun. In some cases, it can take more than 100 hours to capture and collar an individual Roosevelt elk.

In an attempt to close the knowledge gap, CDFW recently initiated one of the largest Roosevelt elk capture and collaring efforts in state history, targeting a population of Roosevelt elk living along the U.S. 101 corridor in Humboldt and Del Norte counties. The effort is part of an ongoing study that began in 2016, explained Carrington Hilson, CDFW’s lead elk research biologist on the north coast. The study will continue through 2025.

Since November, Hilson and her colleagues have affixed GPS tracking collars on 24 cow Roosevelt elk in Humboldt and Del Norte counties to monitor their movements and migrations. CDFW biologists plan to collar another 14 cows this winter.

Several ancillary projects – estimating populations using fecal DNA, looking at calf survival and understanding habitat use – are also underway at Humboldt State University in Arcata in coordination with CDFW that will add to the state’s body of knowledge.

A few factors are driving the research interest, explained Kristin Denryter, the Sacramento-based senior environmental scientist who oversees CDFW’s Elk and Pronghorn Antelope Program. The first is an increasing number of human-elk conflicts along the U.S. 101 corridor that include vehicle collisions, property damage and agricultural losses suffered by north coast farmers and ranchers.

The second driver is technology. Advances in GPS tracking collars make them an increasingly valuable research tool. The new elk collars will record data every six hours over the life of the study and deliver that information daily to CDFW biologists.

Lastly, there is the California Essential Habitat Connectivity Project and U.S. Department of the Interior Secretarial Order 3362 (SO 3362).

Signed in 2018, SO 3362 directs federal agencies to work with California and other western state wildlife agencies to improve the quality of big-game winter range habitat and migration corridors on federal land. The order provided funding for CDFW to acquire the 38 GPS tracking collars and accelerate its research efforts. The collar data will improve understanding of movement and habitat use to inform habitat enhancement on public lands as well as help guide development of potential crossing structures to not only improve habitat connectivity but to also improve public safety by reducing vehicle collisions. CDFW has partnered with CalTrans on improving connectivity as part of the California Essential Habitat Connectivity Project.

A Roosevelt elk stakeholder group made up of CDFW representatives, tribal interests, farmers, ranchers and local officials is also being developed.

Official estimates put the Roosevelt elk population along the U.S. 101 corridor in Humboldt and Del Norte counties at 1,600 animals. Biologists, however, suspect those estimates to be low. In an attempt to reduce growing human-elk conflicts, CDFW issued 20 additional Roosevelt elk tags during the 2019 hunting season through its SHARE program, which provides public hunting opportunities on private land through cooperating landowners. CDFW is currently petitioning the California Fish and Game Commission to increase the allotment of Roosevelt elk tags available along the north coast in the 2020 fall hunting season.

Translocations, limited hunting, high calf survival, and conservation management have all helped boost Roosevelt elk populations from lows in the early 1900s to a robust statewide estimate today of 5,700 animals. Roosevelt elk also occupy parts of Mendocino, Trinity, Shasta, Tehama and Siskiyou counites.

The U.S. 101 corridor population in Humboldt and Del Norte counties has proved particularly adaptable – as comfortable roaming the beaches of state parks as they are grazing in open alfalfa fields or wandering underneath the forest canopy. That’s made them especially popular with tourists and some locals but not so much with farmers and ranchers suffering property damage and crop losses from the expanding herds.

Locations of bird surveys throughout Northern California in a region representing more than 40 percent of all California’s coniferous forests. CDFW has been monitoring wildlife at these locations since 2002 to help inform conservation efforts. Photo courtesy of Dr. Brett Furnas.


An automated sound recorder used to survey songbirds. These devices were programmed to make three 5-minute recordings before, at, and after sunrise –repeated over three consecutive mornings. The timing of the recordings is significant because different species tend to sing at different times in the morning. Photo courtesy of Dr. Brett Furnas.

New research shows climate change may harm migratory songbirds. Saving their forest habitat may help.

Songbirds that travel to northern California each summer from winter ranges in Central and South America appear to be more sensitive to climate change than other types of songbirds, according to new research by CDFW Wildlife Ecologist Dr. Brett Furnas.

In a new paper published in the journal Biological Conservation, Dr. Furnas analyzes 14 years of data taken from the surveys of songbirds living in northern California conifer forests. The bird surveys were done in the Klamath Mountains, Southern Cascades and North Coast Ranges, a region representing 42 percent of all conifer forests in the state.

“The data is especially significant because it is representative of such a large region,” said Dr. Furnas.

Research was completed using automated sound recorders which captured the calls of songbirds at over 1,000 sites between 2002 and 2016. Birds were surveyed at their annual summer breeding grounds about a month after arriving from their winter homes.

Dr. Furnas studied three types of songbirds: year-round residents; short-distance, altitudinal migrants which winter at lower elevations and breed at higher-elevations; and long-distance, Neotropical migrants that winter in Mexico, Central America and South America and breed in California.

“The research alone is an amazing part of this story. Each of the 1,000-plus survey sites required someone to drive to the middle of the forest, hike for an hour or more and install survey equipment,” said Dr. Furnas.

The data shows that Neotropical migrant songbirds are shifting their summer ranges to higher elevations where the climate is cooler. But there’s a downside to the new migration pattern: The long journey reduces the Neotropicals’ flexibility when it comes to breeding behavior. Adjusting to changes in temperature and available food resources in California ultimately hurts their reproductive success.

“Neotropicals’ sensitivity to climate change makes them a conservation risk. It’s unclear if they can adapt as climate continues to warm,” said Dr. Furnas.

There was less evidence of elevational shifting for resident and altitudinal songbirds, indicating they might not be as vulnerable to increases in temperature. This is likely because species that migrate shorter distances – or don’t migrate at all – have more time to prepare for the breeding season. They also have more time to establish a territory, sing to attract a mate and gather food to help raise a brood.

The Neotropicals’ vulnerability is exacerbated by other factors as well. One consequence of the compressed breeding cycle is that the birds can’t afford to tone down singing on hot days when it becomes metabolically taxing. In contrast, resident birds tend to sing less on hot days.

Dr. Furnas sees conservation of mid-elevation conifer forests as part of the solution. Neotropicals are expanding their range to about 5,000 feet and above.

“Middle-elevation conifer forests appear to have features of natural climate refugia. Conserving these forests is crucial,” he said.

However, the natural climate refugia identified by Dr. Furnas have their own vulnerabilities. “If you think of mountains like a triangle, there’s less land area in the middle-elevation forests that Neotropicals are shifting to than in the lower elevation forests they’re abandoning. The availability of forest habitats at higher elevations could be limited in the future due to faster rates of warming at those elevations,” Dr. Furnas said.

For these reasons, the middle zone is a sweet spot for birds. “An increasing number of birds will be crowding into this sanctuary,” he said.

Dr. Furnas’ ultimate message is that research with an emphasis on biodiversity monitoring will be essential to future conservation efforts. Research based on biodiversity monitoring can help identify species and habitats that are most in need of conservation. It can also help conservationists and policy makers assess the effectiveness of conservation actions.

Read Dr. Furnas’ paper: Rapid and Varied Responses of Songbirds of Climate Change in California Coniferous Forests

CDFW Photos. Top Photo: Long-distance Neotropical migrants like the Hermit Thrush may be more vulnerable to climate change than other types of songbirds.

Media Contact:
Ken Paglia, CDFW Communications, (916) 322-8958