Science Spotlight

For generations, anglers in California’s eastern Sierra Nevada mountains fished for one of the most cherished fish in the west, the Lahontan cutthroat trout (LCT). These native beauties are prized for their size, with some growing as large as 40 pounds in the Tahoe Basin.

Sightings of these brown and red native fish have been documented as far back as 1853. But as the population of the state grew, especially during the Gold Rush, the fish were nearly wiped out by mining, development, dams, water diversion and other human factors.

Today, LCT are listed under both the State and Federal Endangered Species Acts, and CDFW has increased its commitment to angling enthusiasts by providing more opportunity to catch this historic fish. This effort includes greatly expanding the number of waters and fish planted in recent years.

Every spring, staff from the American River Hatchery in Gold River make the 100-mile journey from the hatchery to the tiny spawning buildings on the shore of Heenan Lake. This pristine body of water is surrounded by granite peaks in remote Alpine County. It is usually not accessible in the winter, cut off by the snowpack, and is only open to catch and release fishing for six weeks a year. It is also the state’s only source of LCT broodstock (groups of mature fish used as the source for eggs and reproduction). Ultimately, the 800,000 eggs spawned at Heenan Lake each year support recreational angling opportunities at multiple locations in the eastern Sierras.

The staff will make the journey up and down the mountain several times over several weeks to spawn the eggs on site. The process involves carefully bathing the eggs in iodine and suspending them in cheesecloth in aluminum jars about two feet tall, before making the journey back to Sacramento or to other state hatcheries. Some of the eggs head to destinations as far away as Filmore Hatchery in Ventura County.

Once at the hatcheries, the eggs are placed in “hatching jars,” where chilled, UV-filtered river water circulates over them continuously. After two to three weeks, the eyes of the baby fish are visible inside the eggs. These “eyed” eggs will be addled—a process in which the eggs are siphoned through a tube in order to shake them up. This causes the infertile, diseased or dead eggs to turn white, allowing hatchery technicians to easily identify, pick out and discard them. After the fry hatch, they are moved to deep tanks in the hatchery building, where they will spend approximately five months growing before being moved outdoors to large round tanks.

The fish will be planted as fingerlings or sub-catchables (fish that weigh 1/16th-1/6th of a pound) into various high-mountain waterways on the east side of the Sierras. At the time of release, they are still too small to be caught, but they will quickly grow to be trophy-sized fish for the state’s anglers who want to make the journey into the high altitudes.

A tiny, endangered mammal is the subject of an extraordinary conservation effort near the communities of Shoshone and Tecopa in Inyo County.

The Amargosa vole is unique to the Mojave Desert, and today, scientists estimate there are only about 500 remaining in the wild. Though the Amargosa vole is rarely seen by humans, biologists recognize that it is a key link in the native food chain. Predators, including raptors and water birds, share the desert marshes where they live, and the extinction of the Amargosa vole would have a ripple effect on these and many other species as well.

For a year, a scientific team consisting of CDFW, UC Davis and US Geological Survey biologists have conducted intensive research into the life cycle of this little vole. The team visited every marsh that potentially could be inhabited by voles – they mapped the marshes, assessed habitat quality, and determined whether or not voles were present. In a subset of larger marshes the team conducted more detailed assessments of water inflow-outflow, soil moisture and vegetation, and captured voles to estimate local population numbers, assess the health of the voles and take samples for disease and genetics studies. In addition to the hands-on study in the desert, they also studied satellite data to track the amount of vegetation and water in the area over a period of time. A grim picture emerged of a habitat range in decline, due in large part to climate change and human modification.

Some of the findings included:

• Total available habitat for the voles decreased 37 percent between 2012 and 2015.
• Over decades, global climate change has caused a gradual decrease in water in this region. California’s recent drought has exacerbated the problem.
• Of the more than 80 marshes that were documented at the beginning of the study, about 60 have degraded and/or dried up. Those that remain are almost all too small to sustain vole populations. Just as pandas eat only bamboo, the Amargosa vole survives solely on bulrush, a plant that grows in desert marshes.
• Another important finding was that 80 percent of the individual voles found and tracked during the study were adults. This indicates low birth rates and survival rates for juveniles – more barriers to the species’ recovery.

Scientists believe that the network of springs and marshes in the vole’s natural range has been so extensively modified by humans that the vole’s future existence will depend almost entirely on whether humans continue to supply water where and when needed. They found evidence to support this, as an intensive restoration effort at one of the largest marshes showed signs of successfully supporting and sustaining voles.

The report authors identified several specific measures that could be taken to increase vole habitat and improve their chances of survival – including reconfiguring water inflow and outflow, changing elevations and planting vegetation that would enhance existing marshes and/or better connect adjacent marshes.

This study is part of a larger long-term effort to secure a future for the Amargosa vole and the unique marsh ecosystems it depends upon in the Mojave Desert. In late 2014 vole numbers became so low that scientists initiated a captive breeding program at the UC Davis School of Veterinary Medicine to reduce the risk of extinction. Today more than 100 voles are in the captive colony at UC Davis – providing a potential source of animals for release into restored habitats, and an important insurance population to prevent extinction.

Photos by Don Preisler/UC Davis School of Veterinary Medicine

A tiny transponder is placed inside the body cavity of each female salmon. When the fish lay their eggs, the transponders will be expelled, providing scientists with information on when, where and how successful each spawning female is.


After the salmon are tagged, they are returned to a holding pond while the anesthetic wears off.


CDFW scientists electronically identify and perform an ultrasound on each fish in order to assess their pre-spawning condition.


Each salmon in the project received a tiny identity tag that is entered into a database. The computerized system allows biologists to follow individual fish throughout their life cycle.


A team of scientists read, evaluate and record data for each individual salmon.

On Thursday, May 18, fisheries biologists implanted acoustic transponders into 60 endangered adult spring-run Chinook salmon. The transponders will track their movements and help determine spawning success later this season. The salmon will be released to spawn naturally in the San Joaquin River near Friant over the next three months.

Spring-run Chinook have been absent from the river for many decades. Reintroduction is one of multiple strategies biologists are using to reestablish naturally spawning runs of these fish as part of the San Joaquin River Restoration Project. The project – which is jointly coordinated by CDFW, the Bureau of Reclamation, the California Department of Water Resources, the U.S. Fish and Wildlife Service and the National Oceanic and Atmospheric Administration’s National Marine Fisheries Service – is a comprehensive, long-term effort to restore flows to the San Joaquin River from Friant Dam to the confluence of the Merced River and restore a self-sustaining Chinook fishery while reducing or avoiding adverse water supply impacts from restoration flows.

A total of 120 salmon will be implanted and released at two different times. Biologists will track the fish from each release to determine which is most successful. This release strategy provides the hatchery-raised salmon the opportunity to select their own mates, construct redds (a spawning nest in the stream gravel) and spawn naturally.

CDFW photos by Harry Morse

Scientists with the California Department of Fish and Wildlife (CDFW) and Oregon State University recently published the results of a population study on fishers (Pekania pennanti) in northern California and southern Oregon. Led by CDFW Wildlife Statistician Dr. Brett Furnas and three coauthors, CDFW Senior Environmental Scientist Richard Callas, CDFW Research Analyst Russ Landers and Dr. Sean Matthews of Oregon State University, the study produced the first-ever robust estimates of density and size of the fisher population in northern California.

“This is the first time we’ve come up with a solid number of fishers, which is a starting point for tracking and monitoring populations,” Furnas said. “One of the most important tools we have used so far to help this species is reintroductions, so now -- with a baseline established and ongoing surveys planned -- we’ll be able to see if the population is really rebounding over time.”

Fishers in northern California and southern Oregon represent the largest remaining population in the Pacific states. The species once ranged from the state of Washington southward through Oregon and California. Currently, fishers occupy only a small portion of their historical range in that region. In California, fishers are found in the northern areas of the state and a small, isolated population occurs in the southern Sierra Nevada Mountains.

CDFW and the U.S. Fish and Wildlife Service have been petitioned on several occasions to list fishers as threatened or endangered under their respective Endangered Species Acts.

In 2016, while considering fishers in the southern Sierra Nevada Mountains of California, the California Fish and Game Commission voted that the petitioned action was warranted in part, choosing to accept the petition in the context of the Southern Sierra Nevada Evolutionarily Significant Unit, and adopted findings to that effect, which were published on May 6, 2016. Although fishers are relatively well-distributed in northern California and in portions of southern Oregon, data from existing surveys and prior studies was used to estimate abundance. This information is critically important to assess the status of fishers and serve as a baseline for conservation efforts.

Furnas and his coauthors used data from camera traps, hierarchical modeling of detections and non-detections of fishers from the cameras, and information about fisher home range size to develop their estimate of population size. They estimated that approximately 3,200 fishers occur within the northern California and southern Oregon study area, with an average density of 5.1 to 8.6 fishers per 100 square kilometers.

Estimating the sizes of wildlife populations is challenging, particularly for species such as the fisher that are difficult to observe and occur over large areas. A final population estimate for the fisher would not have been possible without the cooperation of a variety of federal and tribal agencies, universities and private landowners who shared datasets that were combined to complete the modeling. With these data, Furnas and his coauthors demonstrated that estimating the population size of the fisher at large geographic scales is feasible. They also suggested that the methods used in their research could be used to estimate the abundance of other carnivores, including black bear, gray fox and coyote.

The study was published in the journal Ecosphere. More information / view publication

Five agencies in two states recently partnered to help a tiny population of Greater Sage Grouse avoid extinction along the California-Nevada border. Biologists from the California Department of Fish and Wildlife, the U.S. Fish and Wildlife Service, Los Angeles Department of Water and Power, the Bureau of Land Management and the U.S. Geological Survey are working together in this first-of-its kind study. On April 22, the bi-state team of scientists captured, inseminated, transported and released 17 of these female upland birds to a new habitat where they will hopefully flourish and repopulate. Eight male birds were also transported to Bodie Hills as part of the study.

The birds were captured near Bodie and moved to Parker Meadows, about 30 miles south. CDFW scientists have been tracking the number of Greater Sage Grouse in Parker Meadows for years, and it was evident that human intervention would be necessary to keep the group alive. Between 2002 and 2010, the number of males had dropped from about 17 to only four, and CDFW estimated that the entire population had a 70 percent chance of going extinct in the next five years.

Translocation was chosen as the best option to save them, as it would not only boost the number of birds in the area, but also immediately widen the gene pool.

The birds were captured at night, measured and radio-collared. The hens were also artificially inseminated with sperm from the males in the Bodie population before being transported and released to integrate into their new home. (Watch video of the capture, insemination and release.)

Although biologists from the U.S. Geological Survey will be doing most of the hands-on work with the birds, CDFW biologists played an important role as well. Environmental Specialist Tim Taylor worked for months to obtain the proper land access permissions and assess the habitat near Bodie. Taylor identified several potential problems (including conifers, where raptors would likely perch while in search of prey, and barbed wire fencing) that needed to be removed prior to the relocation. And Senior Environmental Scientist Scott Gardner, in Sacramento, was instrumental in securing grant funding – without which, this partnership project would not have been possible.

“It’s a long term thing – it’s going to take about five years to get results we are hoping for,” Taylor said. “But we’ve got a great crew and I’m confident we’re going to have success and keep that little population going.”

Read more about the Greater Sage Grouse study.

Photos by Dan Hottle/USFWS