Science Spotlight

Working late, Mojave River hatchery staff apply FDA-certified epoxy coating to hatchery rearing ponds.


CDFW fish transportation truck at Fillmore Hatchery


Acting Mojave River Hatchery Manager Forest Williams at work


A hatchery crew releases trout into the Feather River


A fishy view of trout planting on the Feather River

The beginning of trout fishing season in Southern California is just around the corner, and CDFW biologists and hatchery staff are striving to maximize hatchery trout availability for the many anglers who will cast lines in coming weeks. Trout angling in lower-elevation waters of Southern California generally begins in November and continues through April, to correspond with colder water temperatures that can sustain stocked trout.

Precise temperatures are just one of the criteria that must be met before trout stocking begins. Currently, these conditions are approaching optimal levels, but CDFW is running about two weeks behind schedule due to unforeseen circumstances at Mojave River and Fillmore trout hatcheries, two of CDFW’s southernmost facilities.

The Mojave River Hatchery, built in 1947, raises and stocks a ten-year average of 340,000 pounds of catchable trout per year. Beginning in June of this year, extensive maintenance and facility upgrades necessitated turning off the water for a six-month period. While the completed upgrades will ultimately result in better and more efficient trout production for Southern California, the project ran about two months behind schedule. Water is scheduled to flow again at Mojave River Hatchery in late November and the hatchery will be populated with fingerling trout for fast growth. Mojave’s year-round water temperatures yield fast trout growth resulting in maximized yield in minimal time.

While the Mojave River Hatchery was closed, Fillmore Hatchery, built in 1941 on the Santa Clara River, experienced a significant loss of trout inventory intended for Southern California angling due to gas bubble disease. Gas bubble disease is a result of supersaturated gasses (oxygen, nitrogen and carbon dioxide) present in well water pumped from a deep aquifer. While Fillmore Hatchery is equipped to aerate this water and make it suitable for trout, an unknown variable (possibly a drought-depleted and then recharged aquifer) overwhelmed that ability. In an average year, Fillmore Hatchery produces about 400,000 trout for lakes and streams in Southern California. To reduce fish losses from gas bubble disease in the last several weeks, catchable fish were stocked from Fillmore to appropriate waters, and some fish were transferred to other hatcheries. Ultimately, the gas bubble disease at Fillmore resulted in a loss of about 50 percent of inventory. While emergency measures taken by Fillmore staff and

CDFW fish pathologists resulted in better conditions and lower gas super-saturation, the hatchery must be depopulated so that the issue can be addressed entirely. As soon as all trout are removed, hatchery staff and scientists will increase the gas diffusion capability of aeration towers at Fillmore, in order to handle supersaturated well water for the short and long term.

The status of these two hatcheries presented a substantial problem for trout stocking in Southern California that was solved in part by hatcheries in Central and Northern California. These hatcheries have sufficient catchable size trout to supply Southern California’s approved waters immediately and in coming weeks. Thanks to strategic planning and trout production at a statewide level, Northern and Central California can supply fish to Southern California without impacting originally scheduled trout releases in their respective areas.

Trout stocking for Southern California waters will begin this week and hatchery trucks are on the move. Hatchery staff will work quickly to distribute trout to as many approved waters as possible. Trout stocking to Southern California will initially be lighter than usual, but will likely pick back up in 2018. As Mojave River Hatchery comes back online, fish transferred to that facility will be fed and reared to maximize daily growth. We anticipate another large batch of catchable trout available for Southern California toward early spring 2018.

Hatchery staff will be doing everything possible, statewide, to maximize trout production and releases to approved waters in the coming months. Staff work diligently for the angling public and appreciate their continued support.

The statewide planting schedule is updated in real time online.

CDFW photos. Top: Steelhead trout at Mokelumne River Hatchery

CDFW Environmental Scientist Brian Ehler measures the hind-foot length on a fawn captured near Medicine Lake for a mule deer study.


CDFW Environmental Scientist Brian Ehler measures the hind-foot length on a fawn captured near Medicine Lake for a mule deer study.

Driving up Interstate 5 through Siskiyou County in northern California, one cannot help but take notice of the looming, majestic land mass of Mount Shasta, the largest volcano in the Cascade system.

In this rugged region of the Golden State, mule deer are an iconic species, valued by recreationists and required by wild carnivores who prey upon them for nourishment. Mule deer are considered a “foundation species” because the large landscapes that are necessary for their survival can also be home to a vast array of other wildlife and plant species. But mule deer populations have dramatically declined in recent decades across many western ranges, and in Siskiyou County, this decrease has prompted researchers from CDFW and the University of California, Santa Cruz to partner on a multi-year effort to investigate the population dynamics of this high-profile species.

Since 2015, 51 adult female mule deer and 37 fawns have been captured in the Mount Shasta region. Biological samples, including blood and parasites, have been collected, physical measurements of body condition and age recorded and telemetry collars attached to each subject. Collars on adult deer provide a GPS location every hour and alert researchers when a mortality occurs. The collars also document movement details, including migration routes and the location of critical winter and reproductive ranges. The fawn collars feature location beacons that allow researchers to monitor both general movements and when a mortality has occurred. Once a mortality alert is sent from a collar, a search of the site and an examination of the carcass ensues to determine if the deer died from predation or other causes, such as disease or malnutrition. The collars have timed releases and are set to drop off the animal after 18 months. Researchers can then reuse the collars after retrieving them by following a GPS signal. This high-tech, high-resolution documentation of deer behavior is vital for prioritizing the conservation value of landscapes so they may be better protected in the future.

With the recent arrival of gray wolves to northeastern California, predators are a key focus of the mule deer project. Understanding the influence this large canid will have on natural prey species begins with establishing baselines of how current predators -- including mountain lions, bears, bobcats and coyotes -- are affecting prey in this region. Mountain lions, which rely on deer as the primary component of their diet, are a major focus of this study. Researchers have captured and affixed five adult mountain lions with GPS telemetry collars, allowing them to track and study rates of predation, feeding patterns and diet composition.

The analysis of fecal DNA combined with new statistical techniques is another way to study population density and composition across broad landscapes. DNA analysis allows researchers to determine the sex and identity of an individual deer, which is used to estimate densities and gender ratios. Researchers are collecting fecal samples throughout the mule deer’s summer range, in the hopes of reliably extrapolating estimates of density and sex ratios across the entire region.

This project, which began in 2015, is scheduled to continue into 2019, as researchers strive to gain further insight into the lives of mule deer and predators across this ecologically complex and breathtakingly beautiful region of the state.

California Department of Fish and Wildlife photos.
Top photo: Mount Shasta in winter.

Lassics lupine grows under protective cages.


Richard Macedo, Habitat Conservation Planning Branch Chief constructs a cage to protect rare, endangered Lassics lupine.


Lassics lupine grows under protective cages.

Biologists from three government natural resource agencies banded together this summer in an unusual effort to help preserve a species under threat of extinction. They lugged materials to build wire cages into the rough terrain of the remote Lassics mountains near the border of Humboldt and Trinity counties in an effort to protect their target. However, these cages were not built to trap animals; they were constructed to keep animals out.

The barren, green serpentine slopes of Mount Lassic, located in a seldom-visited part of Six Rivers National Forest, are home to one of California’s rarest plants: the Lassics lupine (Lupinus constancei). Lassics lupine is a short plant in the pea family that has bright rose-pink flowers. Only approximately 450 adult Lassics lupine plants were observed during 2017 monitoring of the species conducted by the U.S. Forest Service and the U.S. Fish and Wildlife Service, with assistance from CDFW.

Rodents such as deer mice, squirrels and chipmunks have been eating so many Lassics lupine seeds from the plants that, absent intervention, the species appears to be on the path to extinction within the next 50 years (Kurkjian et al. 2016).

Biologists believe that historical suppression of fires in Six Rivers National Forest beginning in the early 1900s may be indirectly responsible for the encroachment of forest and chaparral into Lassics lupine habitat. Fires that were put out quickly did not grow large enough to reduce encroaching forest, and therefore the forest expanded. With the encroaching vegetation came more seed-eating rodents that depend on vegetation cover for protection from predators.

In 2003, the U.S. Forest Service, U.S. Fish and Wildlife Service and other researchers began an emergency attempt to halt Lassics lupine’s trend towards extinction. Each summer, biologists set off on the laborious hike up Mount Lassic to place cylindrical wire cages over as many flowering Lassics lupine plants as possible. Each cage is anchored to the ground to prevent rodents from squeezing underneath.

The cages are remarkably effective at stopping rodents when properly installed, and they remain on the plants for the duration of the growing season. After Lassics lupine fruits have matured, they often split open suddenly and send seeds flying through the air up to 13 feet away. The cages are then removed each year before the onset of winter snow.

“Protecting endangered species is California’s policy and plants like the Lassics lupine could disappear within our lifetimes,” explained Jeb Bjerke, a biologist with CDFW’s Native Plant Program. “We should do what we can to save these unique plants for the future.”

In 2015, in the midst of an historic drought, an 18,200-acre fire spread through the Lassics, killing many Lassics lupine plants and charring the chaparral vegetation nearby. The fire had little effect on the forest that encroaches into Lassics lupine habitat, but preliminary studies suggest that the fire may have reduced rodent density in the burned chaparral. Despite the apparent reduction in rodent density following the fire, the impact from rodents eating Lassics lupine seeds remains high. Continued caging of Lassics lupine plants therefore remains critical for preventing extinction of the species until a more permanent solution can be implemented, such as significant reduction of encroaching forest. However, such efforts are expensive to plan and implement. As the primary land manager, the U.S. Forest Service would likely be the lead agency in future protective actions.

In 2016, the California Fish and Game Commission received a petition to list Lassics lupine as an endangered species under the California Endangered Species Act and the species was designated a candidate species earlier this year. CDFW is in the process of producing a status review for Lassics lupine that will include a recommendation to the California Fish and Game Commission on whether listing the species is warranted. The legislature directs all state agencies, including CDFW, to seek the conservation of endangered and threatened species.

“I hope that CDFW can continue to partner with the U.S. Forest Service and U.S. Fish and Wildlife Service to protect the Lassics lupine from extinction,” Bjerke said.

For additional information on this subject, please see:

• Report to the Fish and Game Commission, Evaluation of the Petition from Mr. David Imper and Ms. Cynthia Elkins to List the Lassics Lupine (Lupinus constancei) as an Endangered Species under the California Endangered Species Act (PDF).
• Kurkjian, H.M., S.K. Carothers, and E.S. Jules. 2016. Seed predation has the potential to drive a rare plant to extinction. Journal of Applied Ecology 54:862–871.

California Department of Fish and Wildlife photos by Jeb Bjerke

California leaf-nosed bats. CDFW photo by retired biologist Andy Moore.


Hundreds of bats in flight. ©Dave Feliz, all rights reserved.


Little brown bat with white-nose syndrome. US Fish and Wildlife Service photo.


Townsend's big-eared bat in flight. National Park Service photo.

The last seven days of October are celebrated each year as Bat Week – a time to learn about the importance of bats in our environment.

Bats are nature’s best pesticide. According to a study by the University of California, Davis, Division of Agriculture and Natural Resources, each of these small mammals eats between half and 100 percent of its own weight in insects every night. Some California species consume as many as 600 insects per hour. Imagine living with all the mosquitoes, flies, midges, moths and agricultural pests that are now consumed by bats!

In monetary terms, the natural pest control that bats provide is extremely valuable to the state’s $54 billion per year agriculture and $450 million timber industries. The bats’ appetite reduces the need for chemical pesticides, reduces crop losses and curtails the spread of crop diseases. According to the US Geological Survey, a recent economic analysis indicated that insect suppression services provided by bats to American agriculture is worth something between $4 billion and $50 billion per year.

California Department of Fish and Wildlife (CDFW) Senior Environmental Scientist Scott Osborn notes the estimate’s wide range makes it hard to know exactly how much money bats save farmers. “But even the low estimate, $4 billion, is an impressive amount,” he said. “Bats are an important part of integrated pest management systems.”

As the wildlife trustee agency in California, CDFW is engaged in several activities to help us understand the conservation status of bats in the state, as well as to address threats to bat populations. At statewide, regional and local scales, our scientists have been deploying acoustic bat detectors to determine the distribution of California’s 25 bat species. When CDFW’s bat acoustic data are combined with data collected by partners at other state and federal agencies, academic researchers and non-governmental organizations, we should have more accurate knowledge of where various bat species occur, as well as their seasonal movements.

White Nose Syndrome (WNS) is now a real threat to California’s bats. WNS is a fungal disease that is estimated to have killed more than 6 million bats in eastern North America. With the discovery of WNS for the first time on the west coast (in Washington state) last year, California is bracing for potentially devastating impacts to our bat populations. CDFW is working with the US Fish and Wildlife Service and other partners to conduct surveillance for the fungus that causes the disease, as well as develop plans to manage the disease when it arrives in California. So far, all of the samples collected from bats and their roosts in California have been free of the fungus, but increased vigilance is necessary to help ensure the disease is detected immediately when it arrives. Special measures to reduce the impact of WNS on hibernating bats may include closing caves and other roosts to visitors, because people can unwittingly spread the fungus on their clothing, shoes and gear. Ultimately, it is hoped that ongoing research into the disease will provide tools to either eliminate or control the fungus, both in the environment and in infected bats.

To learn more about the exciting world of bats and how you can “Go to Bat for Bats!” check out the Bat Week 2017 website.

Top photo: A California bat in a crevice. ©Dave Feliz, all rights reserved.

Volunteers from the Society for the Conservation of Bighorn Sheep install the second of three 2,300-gallon water tanks to provide water for wildlife in the Southern California desert.

SCBS volunteer Glenn Sudmeier and Steve Marschke install plumbing fixtures for the sheep drinker at the Cady Mountains guzzler project in San Bernardino County.

Pipes bolted into the rocks coming from a catch pond going to the original guzzler installed in the desert.

Plumbing pipes leading from the catch ponds to the storage tanks at the 40-year-old Cady # 1.

The completed project: Drinkers are covered by fiberglass simulated rocks that shade the water to slow evaporation and to stop algae growth in the opening of the drinker.

Entire scope of the project, with the 150-foot-long catch field in the background that feeds water to the underground tanks.

One of the most elusive species in California is the desert bighorn sheep (Ovis canadensis nelsoni) that live in the dry, desert mountains of southeastern California. Desert bighorn are far from fragile – males are about five feet long and can weigh up to 200 pounds, while the females weigh up to about 150. Despite their size, their keen eyesight and the agility to escape predators up steep rocky slopes, they still face many threats, including disease, human development, expansion and – more recently—a changing climate. Water is critical to their survival in this extreme environment.

The Society for the Conservation of Bighorn Sheep (SCBS), an all-volunteer organization in Southern California, has been working since 1964 for the conservation and management of the desert bighorn sheep. Over the last 40 years, SCBS and CDFW have been installing drinking systems (also called guzzlers) across the sheep’s habitat to help counteract these challenges. Now the populations rely on these water sources to survive and there is a responsibility to keep them functional and maintained.

In September 2017, SCBS rallied the volunteers to install a new drinking system to provide sheep and other animals life-supporting water in the hot summers. The project took place in the desert east of Barstow, and began with the removal and replacement of the very first guzzler ever installed in California.

The old system had two cement catch ponds, each similar to a small swimming pool lined with plastic. The catch ponds collected rain water and funneled it though pipes and valves to three tanks, where it was stored and fed to a small stainless steel drinker box. Due to its age and condition, after being exposed to the desert air and sun for more than 40 years, the system needed constant maintenance, and – more importantly – SCBS members had to haul hundreds of gallons of water across the desert each summer in order to keep the tanks full during the hottest parts of the year.

To improve efficiency and reduce the impact on the habitat, engineers and scientists devised a new approach to the design and installation of the new system. They created a 150-foot-long catch field, laying down three sections of overlapping matting, like tiles on a roof. The mats were then covered with rocks to help it blend into the surrounding area. The mats are made of non-absorbent material that funnels water down a slope where it’s collected and fed into two 2,300-gallon plastic tanks buried in the ground.

SCBS members did all the work to design and engineer the site, dig out the large holes to bury the tanks and install the plumbing and other equipment, including a solar powered satellite telemetry system that will allow scientists to monitor the water levels, ambient temperatures, water flow and other measurements at the remote site.

After four days of morning-to-night labor, the project was completed and the site returned to its near-natural state. Most of the old system was removed with one tank still operating to give the sheep time to find the new water source about 1,000 feet away. The new system is more efficient, requires very little maintenance, and has a higher storage capacity that should eliminate water hauling efforts. The tanks provide enough water for all wildlife in the area, not just the sheep, and they are less visually intrusive from both land and the air, blending well into the desert surroundings.

All this equipment comes at a cost and this construction was paid for with a grant from the CDFW Big Game Management Account (BGMA) that provides money to fund projects that benefit big-game populations and the habitats upon which they depend.

The careful planning and work done will provide a stable and reliable water source for the sheep and other wildlife in this area for decades to come.

To watch volunteers install the new drinking system, watch a video on the CDFW YouTube channel.

Photos of installation courtesy of SCBS. CDFW photos of finished project by Andrew Hughan.