Science Spotlight

  • August 19, 2020

bear in a tree with a tracking collar with the sun rays shining through the trees
A collared bear near Blue Canyon in Placer County.

For years, California Department of Fish and Wildlife scientists were trying to locate dens for California’s Sierra Nevada red fox — a rare and threatened species whose population has decreased substantially. Scientists had a general idea that some of the foxes denned at high elevations in the Lassen Peak area, but aside from vague descriptions written in the 1920s, the den locations had never been documented.

In 2018, a team of scientists led by CDFW wildlife biologist Jennifer Carlson put GPS satellite collars on several Sierra Nevada Red Foxes. They were able to locate several dens in 2018 and 2019 and are in the process of verifying at least two more. Through collar technology and field work they have also verified that the population they were tracking has successfully raised litters.

“Knowing basic information about where the foxes live and breed will help us develop conservation actions to benefit the species,” said Pete Figura, a CDFW wildlife management supervisor who has experience collaring many types of wildlife including deer, elk, Pacific fishers and band-tailed pigeons.

The conservation benefits of collar technology have been well documented. Perhaps slightly less well known is that collars are designed and deployed with animal welfare in mind, allowing study animals to reproduce, get the food they need, maintain a healthy weight and live full lives.

Scientists strive to use collars that weigh five percent or less of an animal’s body weight, and in some cases can use collars that weigh as little as one-and-a-half percent of an animal’s body weight. When possible, scientists use collars that feature a drop-off mechanism which releases the collar before its battery life runs out. The drop-off mechanism also ensures that the animal does not have to live the remainder of its life with an inactive collar. Drop-off collar technology isn’t yet available on some of the smallest collars but may be in the future. Biologists also use expandable collars for young animals that haven’t reached full size, allowing them to grow without being impeded by the collar.

CDFW uses collars that provide two types of telemetry data. The data is derived from three basic approaches:

  1. Collars that send out a VHF radio signal which researchers can detect or listen to with an antenna to determine an animal’s general location and whether it is alive or dead. Researchers must be relatively close to detect the VHF signal.
  2. Collars that passively receive a radio signal from satellites and collect GPS location and other data such as movement and temperature. The data are usually stored onboard the unit which needs to be retrieved and downloaded onto a computer. Some of these collars also allow researchers to download data remotely using a hand-held device, but researchers must be relatively close to the animal. These collars also incorporate the VHF radio signal technology described above.
  3. Collars that also communicate actively to satellites allowing researchers to access location data on their computers and communicate with the collars to change settings remotely (e.g., to change the data collection schedule during migration).

While CDFW collars many types of animals, ungulates (hooved mammals) are the largest group. At any given time, CDFW is collecting data from 500 or more collared ungulates across the state including deer, elk, pronghorn and bighorn sheep. The department collects data on collared ungulates for conservation purposes and to inform hunting limits. Scientists track movement, habitat use and survival and can collect data on everything from ambient temperature to the direction and speed the animal is traveling. Collars can also tell scientists when and where an animal has died and whether it is moving, feeding, or resting.

“We take very seriously our ethical obligation not to harm animals or unnecessarily cause them discomfort. We take great strides to ensure collars have the right fit and weight for the animal wearing them,” said David Casady, a CDFW wildlife biologist with extensive collaring experience.

Collars are typically made from foam and leather with a circuit board housed in strong metal or plastic casing. For data purposes, collars are designed so that the animal doesn’t behave differently than the rest of the population.

“The data we collect from a collared animal needs to be representative of the population at large or it’s not very applicable to our management and conservation efforts,” said Casady.

Data from collars allow CDFW to make well-informed, science-based management decisions. Although scientists in the field often have a solid understanding of the wildlife they research, thoroughly vetted data is what counts in the eyes of decision makers.

Wildlife Biologist Justin Dellinger researches mountain lions (and wolves) for CDFW. He’s seen valuable data come from the 70 to 80 collared lions currently being monitored throughout the state.

“With collared males that move around and look for new territory, data can show us where there’s a lack of habitat connectivity. We can use those data in developing movement corridors and road crossings. It can ultimately help our state’s lion population live full lives,” he said.

Dellinger can also attest to the fact that collared lions are able to reproduce. “A 10-year-old female collared lion that we’re monitoring recently had her fifth litter of kittens,” he said.


CDFW Photos. Top Photo: A collared deer at Bonita Meadows in Tulare County in 2017. The deer was collared as part of a long-term monitoring project.

Media Contact:
Ken Paglia, CDFW Communications, (916) 825-7120

Categories: Science Spotlight
  • August 14, 2020

aerial view of a dirt road with a river running through a low area with blue skies in the background
Drone images helped document damages and clean-up during the 2019 oil spill at Cymric Oil Field near Bakersfield

five scientist in an open field with a target to take off and land the drone with snow capped mountains and blue sky in background
CDFW drone pilots use foldable landing pads that work on multiple surface types—here during a drone mission in Inyo County

In March 2019, there was late winter flooding at the Yolo Bypass Wildlife Area in Yolo County near Davis. Wildlife area supervisor Joe Hobbs wanted to check a series of old railroad trestle mounds to make sure there was no wildlife stranded there. In previous years when there had been flooding, staff went out on a boat to check the trestle mounds. But that approach had downsides: From a boat, it could be difficult to see exactly what was on the mounds, and the sound of the boat’s motor could potentially spook the animals.

Hobbs saw an opportunity to utilize the California Department of Fish and Wildlife’s (CDFW) drone program, a service offered by CDFW’s Geographic Information Systems (GIS) Unit within the Biogeographic Data Branch. He submitted a project request which was ultimately granted.

Drone footage showed two deer on one of the trestle mounds. A CDFW biologist did an assessment and concluded that the water was receding quickly, and the deer were not at risk of being stranded.

“The drone was a great tool for getting the information we needed without causing stress to wildlife,” said Hobbs. “It was quiet and safe and gave us a view of the trestle mounds that we couldn’t get from the ground or in a boat.”

CDFW’s drone program got its start in the early 2010s as GIS Program Manager Steve Goldman and others on the GIS team saw the technology becoming more affordable and useful. In 2014, Goldman put together a dedicated team within the GIS Unit to research policy and best practices. The program officially launched in 2016 when it received its Federal Aviation Administration authorization to fly.

“Drones are very useful for natural resource management because they provide high-resolution aerial imagery and documentation of conditions on the ground in a timely, safe and cost-effective manner that is repeatable,” said Goldman, who also serves as CDFW’s Unmanned Aircraft System (UAS) Coordinator.

Here are a few examples of CDFW drone missions:

  • In 2017, a drone was used to help scientists conduct a bighorn sheep population count outside of Bishop in Inyo County
  • Drone footage helped scientists survey portions of the America River in 2016 to find salmon redds, nests created by salmon in riverbeds where females lay their eggs.
  • As a permitting agency for legal cannabis grows in California, CDFW advises property owners on how to mitigate environmental damage. In 2019, the department used drone footage to assist the buyer of a cannabis property with assessing erosion damage caused by the previous property owner.
  • CDFW has historically partnered with other agencies to do pelican population counts using airplanes over the Tule Lake Wildlife Refuge, a national refuge near the Oregon border. In 2018, CDFW experimented with doing counts using drones to see if results could be achieved more safely and efficiently. Staff found that drones took higher quality images and could potentially yield more accurate counts. Staff also used the mission to assess the disturbance effect of drones and found no disturbance to wildlife.
  • CDFW’s Office of Spill Prevention and Response (OSPR) used drone footage in 2019 to document clean-up efforts in the nearly 800,000-gallon oil spill at Cymric Oil Field near Bakersfield. In March 2020, OSPR utilized drone footage to document clean-up efforts at a tanker truck spill in the Cuyama River in Santa Barbara County.

Because CDFW’s mission is managing the state’s natural resources, the drone program puts considerable focus on minimizing the risk of wildlife disturbance. Before each mission, program staff consult with a biologist to assess the risk of disturbance. If there is any appreciable risk, a biologist accompanies staff on the mission to serve as a wildlife observer. CDFW’s drone program also has a working group to research and catalog disturbance effects by wildlife species. The group’s goal is to minimize wildlife disturbances and develop best practices.

CDFW drone pilots have been fortunate enough to not have any major conflicts with wildlife. But there was one close call. In 2018, while on a training flight at the Yolo Bypass Wildlife Area, a raptor appeared to take interest in the drone. In these situations, pilots are trained to ascend above the bird to get away. Drones can ascend faster than birds of prey can and descend rather slowly.

“The pilot noticed the raptor’s interest early, and at one point the raptor started to come at the drone. The pilot did exactly what he was trained to do – he ascended and got out of the raptor’s way. It wasn’t a dramatic incident, but it did validate our procedures and protocol,” said Goldman.

CDFW has a fleet of 25 drones flown by 14 certified pilots. Additionally, 20 staff are working toward their drone certifications. The current growth is primarily within OSPR and within the Cannabis Lands Program. Certified staff flew 100 missions in 2019. Since the program’s launch, staff have amassed more than 1,800 flights and 300 plus hours of airtime.

“We think we’ve only started to skim the surface of what’s possible with drones. We are excited to continue working with staff to find those opportunities to support our mission,” said Goldman.

Only staff certified through the CDFW’s UAS program are authorized to operate a drone for department work. No personal drones may be used for department work.


CDFW Photos. Top Photo: Image from a drone mission at Sheepy Lake in Siskiyou County

Media Contact:
Ken Paglia, CDFW Communications, (916) 825-7120

Categories: Science Spotlight
  • July 20, 2020

Biologist, Paul Divine releasing a bass fish back in to the lake off the side of a boat
Paul Divine, Lassen County district fisheries biologist for CDFW, releases Largemouth Bass fry into Mountain Meadows Reservoir in 2018 as part of the effort to rebuild a trophy bass fishery that existed before the reservoir went dry in 2015.

scientist hold a bass fish while on a boat on a lake with tall trees in background and blue sky above
Former CDFW Scientific Aid Joshua Faughn holds up a chunky Largemouth Bass that turned up in one of CDFW’s electrofishing surveys of Mountain Meadows Reservoir. CDFW has electrofished the reservoir five times since water returned following the 2015 drought.

biologist holding a small green and yellow pumpkinseed perch fish in his hands on a boat on a lake
Pumpkinseed Sunfish have recolonized Mountain Meadows Reservoir on their own. Biologists believe they survived the drought and the reservoir going completely dry by holding out in one of the reservoir’s creek arms.

Monty Currier’s heart sank when an excited angler told him recently of catching trophy-sized crappie at Mountain Meadows Reservoir in Lassen County.

For the past five years, Currier, a California Department of Fish and Wildlife (CDFW) environmental scientist assigned to reservoir fisheries in the north state, has been working to rebuild the fishery at Mountain Meadows Reservoir after the Pacific Gas and Electric (PG&E) impoundment went dry in 2015 from the combined effects of maintenance work and the drought. Crappie were not part of the restoration plan.

Currier’s spirits lifted when the angler pulled out his phone. The photos he proudly showed off were not of crappie – but rather of good-sized Sacramento Perch, California’s only native sunfish and the result of CDFW transplants from Biscar Reservoir in Lassen County, Lake Almanor in Plumas County and Clear Lake Reservoir in Modoc County.

Anecdotal progress reports such as these have had to sustain Currier of late along with his CDFW colleagues Paul Divine, a district fisheries biologist for Lassen County, and Amber Mouser, who oversees fisheries issues in Plumas County and has worked closely on the Mountain Meadows Reservoir restoration. Plans to formally survey and electrofish Mountain Meadows Reservoir this past spring and next fall have been postponed as a result of COVID-19-related social distancing mandates preventing the work, which typically requires three people working in close proximity aboard an electrofishing boat.

The unfortunate 2015 fish kill at Mountain Meadows Reservoir presented Currier with something of a dream opportunity.

“It’s pretty special because you don’t often get the chance to start from scratch and build up a fishery,” he said. “It takes a lot of diligence, multiple agencies and groups working together to make things happen. There are a lot of moving parts.”

In addition to Sacramento Perch, stocking largemouth bass and seasonal rainbow trout have also been part of the restoration efforts. But before any fish were introduced, CDFW added 600 fish habitat structures in 2016 consisting of brush piles and recycled Christmas trees to jump-start the habitat.

Although Mountain Meadows Reservoir today brims with 5,800 acres surface feet of water, the lake is shallow – at no more than 15 or 16 feet at its deepest point – and heavily vegetated. It offers good habitat to support a self-sustaining largemouth bass fishery and a put-and-take recreational trout fishery in cold weather months. Prior to going dry in 2015, the reservoir offered a trophy largemouth bass fishery and hosted several tournaments and other fishing contests each year.

Rebuilding the popular largemouth bass fishery began in earnest in 2017 with captured bass transplanted from Antelope Lake in Plumas County. In 2018, 2,000 fingerling largemouth bass were purchased from a private hatchery and stocked through the combined efforts of PG&E, the Mountain Meadows Conservancy, local anglers and community sponsors. Last year, largemouth bass were transplanted from Biscar Reservoir. Currier works with CDFW fish pathologists to ensure that the fish are disease-free and safe to translocate.

A spring electrofishing survey would have provided insight on how many bass were now spawning in Mountain Meadows Reservoir. A fall survey would reveal how successful the spring spawning had been.

The last time CDFW had a chance to monitor the recovery was in August of 2019 when two electrofishing boats sampled the western portion of the reservoir. The results were encouraging: 718 fish were captured, the highest catch overall compared to the four previous electrofishing surveys since the reservoir was rewatered.

Fifty-six largemouth bass were captured last August, many being juveniles indicating natural spawning was occurring. Twenty-four Sacramento perch turned up – compared to just three of the fish captured in two previous surveys combined earlier in the year, though well below the 80 Sacramento perch captured in 2018.

The most plentiful species of sport fish in the August 2019 survey was the pumpkinseed sunfish at 417. The pumpkinseed sunfish fishery is very popular at the reservoir, said Currier, and appears to be recovering without the aid of stocking or transplants from CDFW. Currier said the fish likely repopulated the reservoir from one of the creeks that feeds into it.

Currier and CDFW biologists are particularly interested to see whether the pumpkinseed sunfish and Sacramento perch can co-exist over time. Native Sacramento perch, which evolved in the Sacramento-San Joaquin Delta prior to the introduction of non-native sunfish and other predatory species from the Midwest and East Coast, have trouble competing for food and habitat with more aggressive, non-native sunfish such as the pumpkinseed and crappie.

Sacramento perch are an otherwise hardy and adaptable sport fish appreciated by anglers for their fine table fare. CDFW fisheries biologists are constantly on the lookout for suitable waters to expand their range, expose them to more anglers and ensure the species genetic diversity and survival.

Overall, pumpkinseed sunfish accounted for 64 percent of the electrofishing catch in Mountain Meadows Reservoir from 2017 to 2019 compared to Sacramento perch that represented just 7.6 percent of the sampled fish. Three 2019 electrofishing surveys resulted in lower Sacramento perch numbers than in 2018, but CDFW scientists such as Currier note that Sacramento perch can be difficult to electrofish and net due to their dark coloration that makes them difficult to see and their tendency to hold in heavy cover. Other factors such as different water temperatures at the time of the surveys could explain some of the drop-off in Sacramento perch numbers from 2018.

One hundred forty-three Sacramento perch were translocated to Mountain Meadows Reservoir from Biscar Reservoir as recently as June 2019 in an attempt to boost the breeding stock. That anglers are now catching Sacramento perch worth bragging about – even if they are sometimes mistaken as black crappie – is something Currier and his colleagues can take pride in for now.


CDFW Photos. Top Photo: CDFW Environmental Scientist Monty Currier proudly shows off a Mountain Meadows Sacramento Perch, which CDFW introduced into the reservoir to provide an exciting sport fishery for local anglers.

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

Categories: Science Spotlight
  • July 9, 2020

Hallprint, spaghetti-style fish tags provide visual identification for Feather River Fish Hatchery staff that returning salmon are spring-run Chinooks that can be used for spawning and perpetuating the run of fish.

Spring run Chinook salmon receives a fish tag in the Feather River Fish Hatchery
An early arrival to the Feather River Fish Hatchery receives a Hallprint, spaghetti style fish tag identifying it as a spring-run Chinook salmon before it is returned to the Feather River.

Two Feather River Fish Hatchery employees sort and prepare spring run Chinook salmon for tagging
Feather River Fish Hatchery staff prepare spring-run Chinook salmon for tagging before these early arrivals are returned to the Feather River.

group of spring run Chinook salmon swim inside a holding tank within CDFW's Feather River Fish Hatchery in Butte County
Spring-run Chinook salmon inside the Feather River Fish Hatchery.

The California Department of Fish and Wildlife’s Feather River Fish Hatchery in Butte County recently completed the tagging of 2,746 spring-run Chinook salmon in May and June.

The fish were early arrivals to the hatchery. After being outfitted with two external Hallprint, spaghetti-style fish tags on either side of their dorsal fin – two tags in case one comes out and is lost – the fish were returned to the Feather River. Unlike Passive Integrated Transponder (PIT) tags injected into many Chinook salmon smolts in order to monitor their movements, returns and hatcheries of origin, the external Hallprint tags are intended to provide visual identification to hatchery staff of returning spring-run Chinook salmon.

In September and October, the hatchery will spawn spring-run Chinook salmon, selecting among only those returning, externally tagged fish as broodstock in order to preserve the integrity of the spring-run fish and not mix genes with returning fall-run Chinook salmon. The ladder to the Feather River Fish Hatchery was closed July 1 to ensure only the early arriving spring-run Chinook salmon were tagged.

This process helps the hatchery achieve its goal of selecting and spawning salmon that represent the entire timeline of returning fish while keeping spring-run and fall-run salmon separated.

Feather River spring-run Chinook salmon are classified as threatened under both the state and federal endangered species acts. Tagging and spawning efforts help mitigate their decline. The goal is to ensure these native California fish can be enjoyed by generations to come.

CDFW Photos

Categories: Science Spotlight
  • July 6, 2020

Isaac Chellman, high mountain lakes environmental scientist for CDFW’s North Central Region, nets non-native trout from a lake to restore native frog habitat.

Sierra Nevada yellow-legged frog sits among the reeds in its high mountain lake environments with trees and blue sky in the background
The Sierra Nevada yellow-legged frog is listed as a threatened species under both the California and federal endangered species acts.

close up look of a Sierra Nevada yellow legged frog, which blends in well into its native, high mountain lake habitat. The frog is on a dark rock partially in a lake
Non-native trout introduced into high mountain lakes prey upon native Sierra Nevada yellow-legged frog tadpoles and young frogs. Removing these trout from select lakes is an important step in recovering native frog populations.

In the Tahoe National Forest, California Department of Fish and Wildlife scientists are working to balance native species restoration with recreational fishing.

This summer, for the first time in the Tahoe National Forest, CDFW will begin work to restore Sierra Nevada yellow-legged frog (Rana sierrae) habitat by removing introduced trout from four alpine lakes and four small ponds within the Five Lakes Basin area. The Sierra Nevada yellow-legged frog is listed as threatened under California’s Endangered Species Act and endangered under the federal Endangered Species Act. 

The Five Lakes Basin is located in Nevada County, south of French Lake and Faucherie Lake within the Grouse Ridge non-motorized area of the Tahoe National Forest. The area is a popular destination for backcountry recreation. The small lakes and ponds targeted for fish removal include Glacier Lake and are typically accessed from the Grouse Ridge Campground and Faucherie Lake.

“These types of projects highlight CDFW’s dual mission to both provide recreational opportunities and recover native species,” said Sarah Mussulman, Sierra fisheries supervisor for CDFW’s North Central Region. “In this case, we want to ensure anglers have a chance to catch a fish at a beautiful lake while simultaneously ensuring this iconic native frog remains on the landscape for generations to come. Because the fish are a major driver of frog declines, we’ve chosen one area near Grouse Ridge to recover frogs and a nearby area to plant fish.”

To remove the fish, which consist of non-native brook, rainbow and hybridized golden-rainbow trout, CDFW will use mechanical methods including monofilament gill nets and backpack electrofishing units. This project is funded by the U.S. Fish and Wildlife Service through its endangered species recovery grant program and will be conducted in collaboration with the Tahoe National Forest. Work is scheduled to begin by mid-summer and will continue through the fall 2022.

The Sierra Nevada yellow-legged frog was once one of the most abundant species in the Sierra and a critical part of the natural food chain. Non-native trout, which were introduced into historically fishless lakes and ponds throughout the range for many decades, consume young frogs and tadpoles. This predation has been a major contributor to the decline of these native amphibians. The restoration project will provide additional fishless habitat, which is needed for the long-term survival and eventual recovery of this species.

At the same time, CDFW is committed to promoting and maintaining the unique recreational fishing opportunities nearby. CDFW will continue to stock trout into many lakes in the Grouse Ridge area, including Carr, Culbertson, Feeley, Long, Milk, Upper and Lower Lindsey, Big and Little Island, and Lower and Upper Rock lakes. These locations provide fishing opportunities at beautiful, high elevation lakes within a few miles of the Five Lakes Basin.


CDFW Photos

Categories: Science Spotlight
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