Recent accomplishments of CDFW's scientific community
Restoration project area. CDFW photo by Andrew Hughan.
Yellow and orange indicate restoration areas at the Ocean Ranch Unit of CDFW's Eel River Wildlife Area.
How does one best go about making an already bountiful and bucolic part of the Golden State even better? Sometimes, perhaps paradoxically, it pays to look to the past in order to be forward thinking in the present.
CDFW, Ducks Unlimited, and many partners have undertaken the Ocean Ranch Unit of the Eel River Wildlife Area Integrative Ecosystem Restoration Project Planning Process to enhance the estuarine and coastal dune ecosystem of the Ocean Ranch Unit in Humboldt County
The approximately 2,600-acre Eel River Wildlife Area was acquired to protect and enhance coastal wetland habitat, and was designated as a wildlife area by the California Fish and Game Commission in 1968. The initial decision to undertake an estuary restoration-planning project began more than a decade ago. After several years of monitoring to gather necessary data, Ducks Unlimited completed a feasibility study, funded by CDFW’s Fisheries Restoration Grant Program and the California State Coastal Conservancy, in December 2015.
The primary goal is to restore and expand natural estuarine and dune ecosystem functions, including the recovery and enhancement of native species (including fish, invertebrates, wildlife and plants) and their habitats. These changes should also help mitigate current and future impacts of climate change. Sea level rise will likely result in saltwater inundation further upstream, which is expected to modify habitats (for example, the loss of tidal marsh migration inland) and the size and shape of the estuary.
The project has been a revelation for Michelle Gilroy, a CDFW district fisheries biologist who works primarily in Humboldt and Del Norte counties.
“For the first time in my 30-year fisheries career, which began in the Eel River watershed, I am achieving a long-time goal of mine: To envision, develop and work through to completion, or near completion, a large restoration project,” said Gilroy. “This exciting project and the extraordinary team I am so very fortunate to work with is making that dream a reality – and in the Eel River estuary, one of California’s largest estuaries. It is definitely one of the highlights of my career.”
Improving the connectivity of tidal and freshwater habitats, and controlling or eradicating invasive plants, are key goals of the restoration project.
A feasibility study guiding the project analyzed the potential for expanding tidal functions within 475 of the 933 acres of the unit to aide in the recovery and enhancement of estuarine habitat and native species. Restoration of these essential habitats is vital to the recovery of anadromous salmonid populations in the Eel River, as estuaries provide critical nursery and rearing conditions for juveniles prior to ocean entry.
The unit is located within the Eel River estuary, a mile and a half north of the mouth of the Eel River and approximately four miles northwest of Loleta. The unit is comprised of a diverse set of habitats, including coastal dunes, riparian woodlands, tidal mudflats, tidal slough channels, salt marshes and managed freshwater marshes.
Prior to second-wave human settlements, this portion of the estuary, then inhabited by Native Americans, consisted primarily of salt-marsh habitat dotted with areas of spruce and hardwood forest, and native grasslands. An abundant fishery, which included the prized salmon, along with native plants, provided sustenance for the Wiyot people who lived around Humboldt Bay and the estuary. As Euro-Americans settled this region, however, they largely drove the Wiyot people off their traditional lands and began to repurpose portions of the environment.
By the end of the 1800s, most of the salt marsh and forestlands were drained and converted to farm and grazing land. This conversion of tidal marshes to pastures was done with purpose – but such perceived progress carried an ecological cost.
The construction of levees and tide gates to drain salt marsh increased sedimentation, flooding, and the amount and diversity of habitat and food supply for fish and wildlife declined throughout the estuary. This degraded the prior functioning, highly productive estuary ecosystem. In addition, invasive species now threaten the diversity or abundance of native species through competition for resources, predation, parasitism, interbreeding with native populations, transmitting diseases, or causing physical or chemical changes to the invaded habitat.
Despite these declines, the Eel River delta, which includes the Eel River Wildlife Area, today continues to provide vital habitat for many aquatic and terrestrial organisms, including state and federally threatened and endangered fish, wildlife and plant species, and many state species of special concern. More than 40 species of mammals and 200 species of birds use the delta area and researchers have documented at least 45 fish species in the Eel River estuary alone.
The area provides essential spawning, nursery and feeding grounds to several commercially and recreationally important species, including Dungeness crab. Estuaries are among the most productive and diverse ecosystems in the world and are one of the preferred habitats for young Dungeness crabs.
Dungeness crabs use estuaries as critical nursery habitat in their juvenile stages, as not only a refuge from predation – particularly in estuaries with structural habitat such as eelgrass – but also because of the abundance and diversity of prey provided by estuaries. Dungeness crabs are opportunistic feeders – clams, fish, isopods and amphipods are their preferred food sources, as well as other Dungeness crabs. Their predators include those larger crabs, octopuses, and fish, including salmon, lingcod and various rockfishes.
Wildlife, of course, is not the only form of life to reap the benefits of this region, as humans enjoy a range of outdoor activities, including fishing, bird-watching, boating, hiking and hunting.
The project is expected to begin in the summer of 2019.
CDFW photos and map
Top photo: CDFW Senior Environmental Scientist Kirsten Ramey and Eric Ojerholm of the Pacific States Marine Fisheries Commission.
Partners, Funding and Staff
Ducks Unlimited, in partnership with CDFW staff, has recently secured project planning funds from the California Wildlife Conservation Board, and initial project implementation funds from the NOAA Restoration Center. To complete the restoration design and environmental compliance process, this second phase of restoration planning will consist of a continued CDFW and Ducks Unlimited partnership, with additional assistance from several local consultants and a Technical Advisory Committee (TAC). The TAC includes representatives from the U.S. Army Corps of Engineers, the Bureau of Land Management, U.S. Fish and Wildlife Service, National Marine Fisheries Service, California Coastal Commission, California State Coastal Conservancy, North Coast Regional Water Quality Control Board, California Sea Grant, California Trout, Humboldt County Resource Conservation District, Humboldt State University, Redwood Region Audubon Society, private landowners, and the Wiyot Tribe. Additional project partners include AmeriCorps, Tom Origer and Associates, Pacific Coast Fish, Wildlife and Wetlands Restoration Association, GHD Inc., H.T. Harvey and Associates, Moffatt and Nichol, Northern Hydrology Engineering, Pacific Coast Joint Venture, and the Pacific States Marine Fisheries Commission.
CDFW staff who have served on the project management team include Michelle Gilroy, Allan Renger, Scott Monday, Kirsten Ramey, James Ray, Mark Smelser, Gordon Leppig, Michael van Hattem, Jennifer Olson, Linda Miller, Clare Golec, Charles Bartolotta, Robert Sullivan, Tony LaBanca, Mark Wheetley, Scott Downie, Adam Frimodig, Jeff Dayton, Mike Wallace, Vicki Frey, John Mello, and Karen Kovacs.
Surveying Ventura River in Ventura County
Snorkel survey in Hollow Tree Creek in Mendocino County
Hollow Tree Creek steelhead
Taking care of California’s fish and wildlife wouldn’t be possible without managing the resources upon which they depend. To that end, CDFW has an entire branch – and many scientific staff – dedicated to the scientific study, and planning and management of water resources.
Within the Water Branch, CDFW’s Instream Flow Program (IFP) is tasked with collecting and contributing data necessary to make all kinds of important management decisions about ecological function, fish rearing, spawning and migration and habitat suitability.
In the simplest terms, “instream flow” refers to the rate of the water running through a waterway in a natural environment. But when one considers all the interests competing for use of that water – fisherman, boaters, farmers, businesses, water districts, and fish and wildlife themselves – the complexity of the subject is evident.
Measured in cubic feet per second (cfs), instream flow can be measured at different times of the year in a specific location in a waterway. The fluctuations can tell scientists quite a bit about the ecosystem health of a watershed. While some watersheds have flowing water throughout the year and others are intermittent it is often the responsibility of water managers to distribute the water between uses. CDFW, a natural resource management agency, is faced with the complex task of identifying and recommending instream flows necessary for supporting natural resources. Determining instream flows are crucial so that aquatic, riparian, and terrestrial resources dependent on water will be considered and protected during water distribution activities.
Guided by the California Water Action Plan, the Public Resources Code and the Fish and Game Code, IFP staff conduct flow studies, collect field data, develop guidelines for quality assurance, conduct outreach and coordinate with other agencies and interested parties on program-related activities.
In the past year, some of IFP staff’s largest projects have included:
To learn more about these specific projects, please download the IFP’s 2017 Year in Review (PDF) document, available on CDFW’s website.
A Featured Scientist Q&A with the IFP manager Robert Holmes is also available on the CDFW Science Institute page.
CDFW photos. Top photo: IFP staff hold a planning meeting prior to a survey on the Ventura River in Ventura County
Porcupine1: NRVP participants Greg Moore, Mike Maulhardt, Charles Brown and Ben Smith volunteered to service and maintain porcupine stations at Red Lake Wildlife Area.
Not to put too fine a point on it, but studying California’s porcupines hasn’t traditionally been a high priority for CDFW.
Wildlife research funding is limited, especially for non-game species, and species listed as threatened or endangered are typically given top priority. That means that scientists sometimes need to be creative – and frugal – in their efforts to survey and manage non-listed, non-game species.
Stacy Anderson, a CDFW senior environmental scientist specialist based in Rancho Cordova, recently conducted a pilot project that does just that.
Anderson developed an interest in the North American porcupine (Erethizon dorsatum) in 2017, after acknowledging that anecdotal evidence seems to indicate their numbers are on the decline.
Porcupines have historically inhabited diverse habitats including Humboldt County, along the Sacramento River, in the Coast Ranges, the Klamath Mountains, the southern Cascades, the Modoc Plateau and the Sierra Nevada. But in her conversations with unit biologists and wildlife officers in some of these areas, Anderson took note that many were reporting a substantial decrease in the number of calls from residents whose property – typically wood structures such as decks and outhouses – had been damaged by porcupines in recent decades. Informal surveys of veterinarians across the state also indicated a decline in the number of pet owners seeking quill removal from their pets.
Perhaps most telling, CDFW’s Sierra Nevada monitoring project, which has studied portions of the Sierra for the past nine years, has documented only seven porcupine sightings out of 750 stations surveyed via trail camera.
“We are worried about them because we don’t have a lot of sightings,” Anderson said. They live in low densities and they have only have one baby per year, so they don’t repopulate quickly.”
Recognizing the need to gather more information, Anderson and Evan King, another CDFW environmental scientist, launched a pilot effort last year to improve surveillance of porcupine, with a long-term goal of determining distribution and population numbers.
Anderson and King were inspired by the work of Uldis Roze, a researcher who has long studied porcupines in the Catskills of New York by using wood soaked in salt brine as a porcupine attractant. His research indicates that porcupines show a strong seasonality of salt use, which peaks in April through May and August through September. Because porcupines’ diet of plant matter is generally low in sodium (salt), they seek out other dietary sources of sodium to maintain normal levels in their bodies.
Anderson and King theorized that brined wood could be effective in attracting California porcupines, too. A plan was made to soak stakes made from 2x2s in a sodium brine to monitor activity. In theory, tooth scrapings on the wood could also be identified to species.
“It’s not a full-blown study – it’s just a way to test a plan of action that can maybe be used in a study later,” Anderson explained. “We don’t want to waste valuable resources on untested methodology, so this is a way to find out first if the methodology is going to work. It’s a low-cost, high yield approach.”
Twenty-three stations were set up for the 2017 pilot project, which was conducted from April to October. Members of CDFW’s Natural Resources Volunteer Program, who support departmental operations, supplied much of the labor, and the study costs were kept low. Expenses added up to less than $100, including salt for brining and wood. Trail cameras borrowed from other researchers were utilized to help monitor the stations.
Researchers were pleased to learn that the porcupines took to their efforts with a grain of salt (so to speak). They determined that brined-wood monitoring is more effective than traditional bait or game-trail monitoring, at least in the study area in northern Sierra and along the Sacramento River. Preliminary results indicate that the brined wood appeared to lure porcupines into the area of a camera station -- although most did not approach the wood and fewer still left a distinctive chew mark on the brined wood. But the trail cameras provided clear, useful photographs.
“We still have unanswered questions about this technique that will need to be addressed before we can consider it a success,” Anderson said. “However, our pilot efforts are promising.”
CDFW is seeking additional funding through state wildlife grants and collaborative efforts with other researchers and agencies to gain a better understanding of the North American porcupine’s status. Anderson plans to continue refining the methodology of her study, along with other survey techniques including habitat surveys, feeding signs, tree girdling, scat searches and the use of detection dogs.
Anderson also encourages members of the public to help CDFW’s efforts by reporting detections of live or “roadkill” porcupines.
CDFW Photos. Top Photo: Porcupine photo by CDFW Warden Chad Alexander.
The tilapia skin is visible on the bottom of the bear's paw.
Veterinarians perform an ultrasound to check on the progress of the second bear's pregnancy.
Acupuncture needles assist with pain management.
After placing the second bear, the team moved the first bear to another location where another man-made den awaited.
CDFW staff work together to build a makeshift den for a soft release in Los Padres National Forest. A soft release involves putting the bear in a den to simulate hibernation, and leaving it to wake up on its own.
Two talented veterinarians, an environmental scientist and several dedicated staff members at the CDFW Wildlife Investigations Lab recently put their heads and their resources together to help heal a pair of adult bears that were badly burned in the Thomas Fire. The bears, which were treated at the same time as a young mountain lion with similar, less severe burn injuries, were released back to the wild last Thursday, after several weeks of intensive – and unusual – care.
CDFW Senior Wildlife Veterinarian Dr. Deana Clifford was acting manager of the Wildlife Investigations Lab in Rancho Cordova when the first bear – an adult female weighing about 200 pounds – was captured inside of a backyard aviary in the Ojai area on December 9. With CDFW Environmental Scientist Christine Thompson coordinating, CDFW Wildlife Officer Jacob Coombs darted the bear and local veterinarian Dr. Duane Tom evaluated its injured paws and overall condition. Thompson then conferred with Clifford, who determined the bear might have a chance at recovery if treated quickly. The bear was put into a trailer for the seven-hour transport to Rancho Cordova, where Clifford was waiting.
By the time the bear arrived, Clifford had already reached out to Dr. Jamie Peyton, Chief of Integrative Medicine at the UC Davis Veterinary Teaching Hospital, for help. Weeks earlier, Peyton, who works mostly on domestic animals, had mentioned to Clifford in passing that she had a particular interest in animal burns, and would be interested in helping wildlife if the chance ever arose.
Peyton created a homemade burn salve for the bears’ paws, and a process for sterilizing tilapia skin. Fish skin, which contains collagen, is often used by doctors in Brazil to bandage human burns. The technique is not yet approved by the Food and Drug Administration for use in the United States, and had not been tried on veterinary patients.
To help keep the tilapia skin in place, Peyton cut pieces to exactly match the size of the bear’s paws and then sutured them over the wounds while the bear was under anesthesia. Additional temporary wrappings, including rice paper and corn husks, were added, with the intention of stretching out the amount of time it would take for the animal to chew down to the fish skin bandage. “We expected the outer wrapping to eventually come off, but we hoped the tilapia would keep steady pressure on the wounds and serve as an artificial skin long enough to speed healing of the wounds underneath,” Peyton said. She also used acupuncture to aid the bear with pain management.
The original plan was for Peyton to come to the lab weekly to check on the bear’s progress. But within just a few weeks, two more burn patients arrived from the Thomas Fire. A second adult female bear, found relatively close to where the first one was found, was brought to the lab by Thompson on December 22. And on December 23, the young mountain lion arrived from Santa Paula. The experimental tilapia treatment was extended to the two newcomers as well.
Of the three animals, the mountain lion’s injuries were the least severe. Because of his young age, he was earmarked for placement in a wildlife rescue facility. The two bears were in much worse condition, with oozing wounds and, in some cases, paw pads that were completely burned off. But because the bears were older and stronger, the veterinarians hoped to return them to the wild if their injuries could be healed.
To complicate matters further, on December 28, during a routine burn treatment, Clifford’s team performed an ultrasound on each bear, and found that the second bear was pregnant. The quest to heal the mother-to-be was now a race against time.
“That was a game changer for us, because we knew it wouldn’t be ideal for her to give birth in confinement,” Clifford said. “We aren’t really set up to have a birth at the lab holding facilities, and we knew there was a high probability that she could reject the cub, due to all the stress she was under. We needed to get her back into the wild as quickly as possible.”
While Clifford and Peyton continued to focus on healing the animals’ injuries, Thompson started scouting out potential release locations. Since both bears needed to be transported back to Southern California, it was decided to try to return them at the same time – albeit not exactly in the same location – in order to make the best use of staff time and resources.
Both bears’ original habitat had been destroyed by fire, so Thompson scouted for two new locations that fit several parameters. The bears needed to be close to their home range, but not within the burn area, and near ample food and water sources. She also wanted to keep them as far away from each other as possible. “A lot of wildlife habitat was destroyed by the fire, and there are already a lot of displaced animals roaming around,” Thompson said. “So there’s a good chance that whatever location we choose is already occupied by other bears, but only they know exactly where that designated territory is. The best we can do is make an educated guess, and place them as deep into wild lands as possible.”
Taking the rapidly changing winter weather reports into careful consideration, the team chose Wednesday, January 17, as the target date to get on the road. That morning, Peyton came to the Wildlife Investigations Lab one last time and both bears were immobilized for a final treatment for their feet. Then the bears were placed into separate transport trailers for the long journey home. Simultaneously, in the Los Padres National Forest, Thompson and Tom spent the day digging dirt and moving logs to create a winter den for each bear.
“At this time of the year, most bears have established dens for the winter, but since these bears won’t have time to create a den, we hope to improve their chances of survival by creating a den for them so they have a home base and shelter right away,” Clifford explained.
The team arrived late Wednesday night, and both staff and bears were hosted overnight by the Ventura County Sheriff’s Department. Early on the morning of January 18, Clifford, Thompson, Coombs, Tom and their team drove the bears deep into the forest for the final leg of their journey. One at a time, each bear was sedated and carefully placed into her den, while the team finished constructing a shelter around the slumbering animal. The bears are about five miles apart, as the crow flies, and each is wearing a satellite collar so CDFW can monitor her movements and survival post-release. Staff also placed trail cameras near each den.
“We’re really hopeful that these novel treatments accelerated the healing for these bears and provided them the best odds of survival,” Clifford said. “It’s especially good to know that we’ve maximized the odds of survival for the cub on the way. We don’t know exactly when it will be born, but hopefully we’ll be able to monitor the movements of the mother via satellite, and that will give us an indication of how things are going.”
For Clifford, the entire experience wasn’t simply about saving the lives of two bears. The bigger picture involves the body of knowledge the experimental treatment provided – both to the Wildlife Investigations Lab team and to the UC Davis Veterinary Teaching Hospital.
“This treatment has the potential to be used successfully on all kind of burn patients, both domestic and wild,” Clifford said. “For us, at the Wildlife Investigations Lab, it’s been an invaluable experience because California’s changing climate means that we’re likely to see more wild animals impacted by catastrophic wildfires. By better understanding what resources are needed to care for injured wildlife and what treatment techniques increase healing speed, we can make the most informed treatment decisions, reduce animals’ time in captivity and provide guidance to other facilities caring for burned animals.”
CDFW photos. For more, please see CDFW’s Flickr photo album: Thomas Fire Bears.
Top photo: The first bear rests in her holding enclosure after her treatment is finished. The outer wrapping on her feet (made of corn husks) will delay her efforts to chew off the tilapia skin bandages underneath.
Recently at Bay Marine Boatworks in Richmond, CDFW’s Bay Delta Region accepted delivery of a new research boat. Funded by the California Department of Water Resources and the United States Bureau of Reclamation, the 32-foot-long aluminum boat is now part of the fleet dedicated to collecting data for the Interagency Ecological Program (IEP), a consortium of state and federal agencies that have been working together on ecological investigations since the 1970s.
Berthed in Antioch, the boat will be named after a native fish or aquatic invertebrate, and will be christened later this summer. It will be put into service for field work (trawls) mandated for the protection of endangered fishes — especially Delta Smelt and Longfin Smelt — in accordance with state and federal water projects.
The yet-unnamed boat was built and rigged for CDFW specifically to meet the needs of research in the Delta. It features a very sturdy hull and an emphasis on “trawl hydraulics.” Built by Munson in Burlington, Washington, the bright gray boat has a top speed of 25 miles per hour and can carry 4,500 pounds (combined crew and cargo). It has a 10-foot beam (width) that will allow the crew to work safely, and uses two trawl winches for towing nets far behind the boat. The boat’s 473-hp diesel engine uses a special ‘trolling valve’ to tow nets at just one mile per hour. The slow speed is crucial because the nets have very fine mesh designed to catch very small fish.
The vessel is the first new boat that Bay Delta Region's IEP Operations Program has received in 13 years. To avoid increasing the number of boats in the fleet, it replaces a 1995-vintage boat that was far smaller (16 feet) and relegates the Beowulf — a notoriously unreliable 1989-vintage 25-foot trawler with no toilet and very little seating — to the status of back-up boat.
“Water-based science is an essential function for this department, and our biologists put in many long hours on these boats. Their safety is imperative,” said Marty Gingras, IEP program manager. “This new vessel is versatile, cost-efficient, safe and green – and it will play a very important role in our efforts to manage threatened and endangered fish populations in the Delta for years to come.”
Eventually, CDFW hopes to replace other boats in the fleet, including the 50-year-old Striper II, which scientific crews use for striped bass and sturgeon surveys.
Tim Hermansen of CDFW carries a turkey holding box to CDFW’s Levi Sousa while John Davis clears the net.
Derek Schiewek of CDFW holds a turkey while CDFW’s Laura Cockrell measures the tarsus.
Recent efforts to determine the number of turkeys on the Upper Butte Wildlife Area have been a net success.
CDFW staff and volunteers from the National Wild Turkey Federation (NWTF) began annual turkey banding efforts in 2015 to gather information about turkey demographics and movements to facilitate better management of the population and assess future hunting opportunities. Approximately a dozen volunteers and staff have since worked on this effort two months each year, in the late winter through early spring.
Captured birds are fitted with a numbered band, and their age, gender and weight are determined before they are released. The number of times a turkey is recaptured through ongoing trapping activities, or when a hunter returns a band to CDFW, provides data about the density and the movements of the birds. Approximately 20 wild turkeys have been captured each of the past four years, using air cannons that propel nets. Last year was the sole exception, as torrential storms resulted in zero captures because portions of the property were flooded and could not be traversed with trapping equipment.
“That year was very frustrating, but part of being a wildlife biologist is going with the flow,” recalled CDFW Environmental Scientist Laura Cockrell, who is involved in coordinating and facilitating wildlife surveys on the wildlife area.
This year, walk-in traps were used for the first time to supplement the traditional use of air cannons, and the final tally was 38 turkeys banded, increasing the total number banded over the course of the project to 88. This baseline data will inform decisions on how many turkey hunters will be allowed access to the wildlife area each spring.
“Our volunteers and all our staff are what makes this project successful,” Cockrell said. “Everyone completes a safety training so we can make sure the birds are handled quickly and carefully, and then it is a lot of ‘hurry up and wait’ during the trapping operations. If we did not have a dedicated crew on this project, it would not be successful. The walk-in traps allow staff to set up trapping operations in the morning, check the site throughout the day, and process birds as they are captured.”
Also appreciative of the banding efforts were turkey hunters, who had an extra “spring” in their step this year at the Upper Butte Wildlife Area.
The 2018 spring turkey hunts recently ended after 64 hunters who hunted on Upper Butte Basin harvested 35 turkeys. During the previous three spring seasons combined since spring turkey hunts began on the wildlife area in 2015, 133 hunters participated and 47 turkeys were harvested.
All the result of field conversations between CDFW staff and fall turkey hunters.
“During the fall turkey seasons some years back, hunters at the check stations would frequently ask us when we were going to offer a spring season, which we had not done before,” Cockrell said.
At the wildlife area’s Howard Slough and Little Dry Creek units, the problem was not a lack of turkeys but rather a lack of funding to hire staff to advertise, prepare, regulate and operate the extra hunts – and a lack of scientific data to support an extra hunting season.
A collaborative effort between CDFW and the NWTF solved that problem.
In 2014, NWTF applied for and received a state grant from the Upland Game Bird Stamp Fund. The grant proposal, which was spearheaded by NWTF District Biologist Kevin Vella, obtained five years of funding to support a seasonal coordinator position.
“This spring we had almost 1,800 applications for 144 open spots,” said Cockrell. “Our hunters really appreciate the opportunities that the spring turkey hunts provide. We frequently hear after a hunt what an amazing time they had out in the field and how much they enjoyed their time on the wildlife area. One of our hunters this season was so excited because he was able to harvest a nice turkey at his very first hunt!”
All photos © National Wild Turkey Federation, all rights reserved. Top Photo: Tim Hermansen of CDFW holds a turkey while Laura Cockrell of CDFW measures its beard with calipers.
It does not take a leap of faith to believe that CDFW scientists have gained the upper hand in bolstering the population of yellow-legged frogs in the High Sierra.
Over the past three decades, Sierra Nevada yellow-legged frogs have become imperiled in California due to the two-pronged impact of introduced (non-native) trout and chytridiomycosis, a disease that is affecting amphibians worldwide.
Past introduction of non-native fish, including rainbow trout and golden trout, to benefit sport fishing in the High Sierra took a heavy toll on the species. High-elevation lakes where these frogs once flourished were largely fishless until fish stocking came into vogue. As the years passed, scientists determined that these introduced fish were depopulating the frogs by competing for food sources (primarily insects) and by predation (trout ate both adult frogs and their tadpoles). Chytridiomycosis, which affects many frog species, also impaired the ability of the Sierra Nevada yellow-legged frog’s skin to exchange vital nutrients, which often leads to death.
As a result, Sierra Nevada yellow-legged frogs are believed to have vanished from approximately 92 percent of their historical habitat, and halting and reversing that decline has become an important goal of CDFW, as well as other state and federal entities.
“This is an animal that only lives in the Sierra Nevada,” said Sarah Mussulman, a CDFW senior environmental scientist. “It is one of our unique California species that lives in high-elevation areas, and as an amphibian it serves as an important link between the terrestrial and aquatic ecosystems. This link is especially critical in the low nutrient, granitic basins of the High Sierra, where frogs and tadpoles consume insects and algae and are themselves consumed by a variety of snakes, birds and mammals.”
CDFW recently completed two projects as part of its ongoing efforts to reverse the population decline of Sierra Nevada yellow-legged frogs.
The efforts took place at two sites: Highland Lake and Clyde Lake, located approximately seven miles apart on the Rubicon River in the Desolation Wilderness area of El Dorado County. The projects were completed with federal grant funds earmarked for the recovery of endangered and threatened species (the species is listed as threatened by the State of California and as endangered by the U.S. Fish and Wildlife Service).
Highland Lake, along with its outlet, an unnamed stream, and two small adjacent ponds, supported a small population of rainbow trout when the project began in 2012. Trout abundance had declined in the absence of stocking in recent years but sufficient natural reproduction occurred in the inlet to Highland Lake to sustain the population. CDFW began using gill nets to remove rainbow trout -- the descendants of fish planted in the lake by CDFW from 1935 to 2000 -- in 2012, in partnership with Eldorado National Forest personnel.
During a frog-monitoring survey at Highland Lake in 2016, approximately 800 adult frogs were observed, as compared to a 2003 survey in which only a few tadpoles were observed. Because the frogs have consistently survived in this area despite the presence of chytridiomycosis, scientists believe they have a good chance at persisting in the area for a long time.
“Highland really had a population explosion over the past five years and can be counted as one of the most successful projects of this type ever undertaken,” Mussulman said.
The project at Clyde Lake was smaller and had somewhat different factors.
Golden trout, which frequently have the same negative impacts on Sierra Nevada yellow-legged frogs as rainbow trout, including predation and competition for food sources, were planted by CDFW at Clyde Lake from 1932 through 2000.
Once stocking was halted, the golden trout proved less resilient then the rainbow trout at Highland Lake, due to habitat factors.
“Clyde Lake sits in a north-facing granite bowl bordered by 1,000-foot cliffs, and no flowing streams enter the lake,” explained Mussulman. “There was no spawning habitat, which is likely why golden trout did not persist there after stocking was halted.”
The stream flowing out of Clyde Lake and four nearby ponds did support a small population of golden trout after plants were halted. The fish in the stream and ponds, which are self-sustaining populations, are precluded from moving from the stream into Clyde Lake by a fabricated dam. In 2013, frogs and a few tadpoles were observed in the stream alongside fish, and CDFW began removing the fish from the stream with gill nets to provide additional habitat for the frogs.
Nine years of monitoring data collected by CDFW scientists indicate that the area’s Sierra Nevada yellow-legged frog population, while small, is slowly increasing. Surveyors observed more than 120 frogs in 2016, compared to a low of six observed in 2005. Moreover, in 2016, for the first time, dozens of tadpoles were observed in the newly fish-free lower reaches of the stream.
“It is great to see these populations recovering,” Mussulman said. “It is a great privilege doing this work that helps keep these frogs on the landscape.”
CDFW photos: Highland Lake in the Desolation Wilderness, and a Sierra Nevada yellow-legged frog
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