Science Spotlight

Close-up of adult spring-run Chinook salmon dorsal fin.


Adult spring-run Chinook salmon inform river restoration decisions by their habitat use and preferences.


Adult spring-run salmon are carefully selected for release based on their sexual maturity.


Spring-run Chinook salmon released into the San Joaquin River are outfitted with three tags including a colored T-bar tag for visual identification.

Fresno County may seem an unlikely setting for salmon restoration and research, but some of the California Department of Fish and Wildlife’s (CDFW) most ambitious work with salmon anywhere is taking place in the heart of the parched Central Valley.

Since September, CDFW fisheries biologists have been spawning spring-run Chinook Salmon broodstock in the shadow of Friant Dam on the San Joaquin River. This season, CDFW staffers spawned 100 mature females that ranged in age from 3 to 6 years old  producing about 290,000 eggs.

It’s all part of an unprecedented, multiagency effort to restore an extinct, spring-run Chinook Salmon run to the San Joaquin River that is happening alongside river restoration efforts to make the river more salmon-friendly for a fish listed as threatened under both the state and federal Endangered Species Act.

Historically, spring-run Chinook Salmon were the most abundant salmon species in the Central Valley. Today, there are so few fish broodstock used for spawning comes from eggs collected at CDFW’s Feather River Hatchery in northern California. Meanwhile, construction is underway on a spring-run Chinook Salmon hatchery at the base of Friant Dam to support future runs of San Joaquin River salmon. The hatchery is scheduled to be completed in 2019.

During spawning, each female is crossed with four males to maximize genetic diversity. Samples of ovarian fluid are collected and sent to the CDFW’s Fish Health Lab for virology and bacterial analyses. Any egg lots determined to be potentially infected with pathogens are excluded from CDFW’s captive rearing program.

In June and August, 179 captive-reared adult fish – 59 females and 120 males – were released into the San Joaquin River to monitor what parts of the river the salmon prefer for holding and natural spawning.

Prior to release, each fish was outfitted with three tracking devices – an electronic passive integrated transponder (PIT) tag for individual identification, a colored, T-bar tag for visual identification, and an acoustic transmitter so their movements in the river can be monitored and recorded. Their habitat use and preferences inform river restoration efforts.

Spring-run Chinook Salmon spawn in the fall from mid-August through early October. So far, biologists have found 37 constructed redds – or salmon nests – in the San Joaquin River indicating some of the released salmon found enough cool water in the heavily damned and diverted river system to survive the Central Valley’s furnace-like summer and are now actively spawning in the river.

CDFW Photos by Travis VanZant. Top Photo: Prior to their release into the San Joaquin River this past summer, adult spring-run Chinook salmon were outfitted with acoustic transmitters so their movements in the river can be monitored and recorded.

This CDFW map shows the routes
and distances traveled by both bears
since being re-released in January.


The older bear, safely on her way
back to the wilderness after being
tranquilized in Montecito by a wildlife
officer on April 2. (CDFW photo)

We have an update on the two black bears that were burned in the Thomas Fire in late December/early January! Both bears were suffering from extensive burns to their paws when they were brought to CDFW’s Wildlife Investigations Lab in northern California. Under the care of CDFW Senior Wildlife Veterinarian Dr. Deana Clifford and Dr. Jamie Peyton of the UC Davis Veterinary Medical Teaching Hospital, the bears were given an unusual experimental treatment involving the use of sterilized tilapia skins as bandages. After the bears were well enough to survive on their own, they were returned to the Los Padres National Forest, as near as possible to where they were originally found. Both have covered many miles and each has been spotted at least once since their release.

The younger bear was seen in an avocado orchard on May 29 by a biological consultant conducting a bird nesting survey. The bear ran away, which is a good sign that she has not become habituated. The consultant was able to get photos and video of the bear, who appears to be in good physical shape.

The older bear, who was pregnant during treatment and at the time of her release in January, came down from the hills and wandered into the town of Montecito on April 2. A local wildlife officer tranquilized her and returned her to suitable habitat, and she’s stayed away from people ever since. Though she was reportedly in good general health, there has been no sign of a cub, so the pregnancy may not have been carried to term or the cub may not have survived.

GPS collars on the bears allow CDFW biologists to track the animals’ movements so they can see where each one has been. Data shows the younger bear usually stays near Fillmore, but has made the 10-mile trek back to her release site in the Sespe Wilderness Area at least three times. She also made a brief trip over to Highway 5, north of Castaic. The older bear spends most of her time in the hills above Ojai. “We are encouraged and so pleased that both bears have survived for eight months now after burn treatment and release – they have walked hundreds of miles on their treated feet by now,” Dr. Clifford said.

CDFW will continue to monitor the movements of both bears via their satellite collars for at least another year. The data will ultimately help scientists build their knowledge of how animals utilize landscapes affected by large fires.

Read the original story of the Tilapia Bears at: https://tinyurl.com/y849mru7

Top photo: The younger of the two bears, as seen in an avocado orchard on May 29. (Photo by Jessica West)

It’s just before dawn in the eastern Sierra Nevada Mountains in Mono County. It’s a cold clear morning, a good day to be out experiencing a still very much wild area of California. California Department of Fish and Wildlife (CDFW) biologist Justin Dellinger and a Wildlife Services houndsman are preparing gear to go out looking for fresh mountain lion tracks in this vast landscape. With the help of a team of highly trained dogs, Dellinger and the tracker are focused on the ultimate goal: Capturing a mountain lion and outfitting it with a GPS collar for research purposes.

This tracking effort in Mono County is part of a larger project to estimate mountain lion population size statewide. It began in the southern Cascades and northern Sierra-Nevada Mountains in 2015, and since then CDFW has solely undertaken or collaborated on similar efforts in the north coast, Modoc plateau and here in the eastern Sierra Nevada Mountains. It’s tough work with long hours; trackers can spend days or even weeks in pursuit of lions. Yet tracking remains the gold standard method of gathering data in the mountain lion research world.

Notably, it takes both biologist and houndsman, each with a unique skill set, to make this team effort work. On this particular day, for example, Dellinger starts the ball rolling when he spots a fresh set of mountain lion tracks made the night before. The mark of the hind heelpad, measuring 52mm across, indicates that it’s a tom (male cat) heading southwest. The long stride suggests he’s traveling in a focused and determined manner – perhaps to secure a meal, locate a mate or confront another male trying to move in on his turf.

Dellinger radios the houndsman, who is astride a mule. The houndsman makes his way to the tracks with dogs in tow, where he assesses a wide variety of information – the time of day, wind speed and direction, topography, etc.

“The mental calculations (of the tracker) are rooted in decades of experience and know-how, but they’re still somewhat of an enigma to me,” Dellinger says. “But then again, houndsman feel likewise about the statistical calculations employed by biologists. It takes both of us, working together, to compile all the information and derive a solid population estimate.”

Over the next several days, the houndsman and the biologist follow the tom over miles of country, with the cat none the wiser about his pursuers. The team eventually catches up to the tom. The dogs masterfully trail him over boulders and around escarpments and tree him in a pinyon pine. The houndsman signals to Dellinger that the tom is treed. Dellinger then works his way into position to dart the animal. Success! Within an hour, the cat is asleep and Dellinger is able to affix a collar.

Yet despite the enormity of the overall effort, the day’s accomplishment is only one small step in the overall plan. Simply put, they’ll get a little rest and then wake up and try to do it all over again tomorrow.

As CDFW’s lead mountain lion biologist, Dellinger understands the need to study and understand Puma concolor only too well. “Lions are the apex predators across much of California, and apex predators can tell scientists a lot about the ecological wellbeing of a given landscape or ecosystem,” he explains. “If mountain lions are decreasing in an area, it’s likely that prey species are decreasing too. If mountain lions are exhibiting health issues, it’s likely that other animals in the ecosystem are experiencing similar issues.”

Because of those grants, this first comprehensive effort to collar lions around the state is now underway. It’s a huge and somewhat daunting task. California’s size and ecological diversity requires a divide-and-conquer approach, meaning that studies can only be conducted in one area at a time. Together, those “slices” of data will add up to a statewide picture. 

Getting the collar on the cat might be the most important part, but all of the data Dellinger collects on this trip will be useful. He’ll be able to compare tracks and remote game camera photos with GPS collar data to derive a minimum count of mountain lions in the area. For now, this is the best way of counting mountain lions in the western United States. In the future, CDFW may grow to rely on data gathering techniques that are more cost- and time-effective than tracking, and use more common skill sets. One possible alternative is developing thanks to the rapid advance of using genetics to monitor wildlife species without having to handle the animals. Scat samples can be collected and analyzed to provide a genetic fingerprint of the animal that deposited them. In theory, if enough lion scat is collected over a large enough area, CDFW can estimate the number of lions in the area.

But scat analysis is still a fairly new way of doing things, and until techniques can be tested, compared and perfected, CDFW will continue to employ the tracking “gold-standard.” The newer methods can be compared to the old, and it’s possible that the newer methods will outperform (i.e., be cheaper and just as reliable) the older methods in some areas but not other areas.

CDFW sees this statewide effort as a first step in monitoring and conserving the elusive, ecologically important mountain lion long-term in California. The project is still in its early stages and will likely continue for another six years or so. Dellinger is enthusiastically looking forward to the work. “It’s really cool because no other state has attempted such a comprehensive population assessment of lions … and  no other western state is as ecologically diverse as California,” he says. “Doing something this comprehensive requires working in a lot of very unique areas. It’s never going to be boring.”

Photos courtesy of Justin Dellinger

These pregnant females will bolster the population of a newly established herd as well as provide an infusion of fresh genetic material to helps ensure their new herd’s health and long-term survival.


Outfitted with an ear tag and two tracking collars, this ram awaits delivery to a new herd where it’s hoped he will infuse the population with fresh genetics


Among the goals of the Sierra Nevada Bighorn Sheep Recovery Plan is the establishment of 12 viable herds across their historic range. CDFW’s capture and relocation efforts over the years have helped establish 14 herds today across 150 miles of their historic range.


These Eastern Sierra bighorn sheep are being prepared for their flight to a new home and new herds.

Seven animals.

Can just seven Sierra Nevada bighorn sheep really make much of an impact on the species’ future?

CDFW scientists believe so, which is why they came away pleased with the results of their annual spring helicopter capture this past March. Limited to three days of work due to strong winds and bad weather, the effort resulted in the capturing, collaring and relocation of seven sheep to new herds high in the Eastern Sierra.

Although the final chapters have yet to be written, the saga surrounding the Sierra Nevada bighorn sheep, one of the rarest large mammals in North America, is shaping up to be a 21st century wildlife success story.

A unique subspecies found only in the Sierra Nevada, historic populations numbered in the thousands. Their steep population decline began in the 1800s as a result of competition from livestock grazing, unregulated hunting and the transmission of disease from domestic sheep. Drought and predation further hammered their numbers, which dwindled to about 100 animals in just three herds by the mid-1990s. State and federal officials declared them endangered in 1999.

Today, less than 20 years removed from those dramatic listings, there are 14 different Sierra Nevada bighorn sheep herds spread across 150 miles of the iconic mountain range. About 600 bighorn sheep are now eking out a living atop the Sierra’s highest peaks. Sierra Nevada bighorn sheep are present once again inside Yosemite National Park and Sequoia National Park after a 100-year absence.

CDFW’s role is itself unique as a state agency tasked with leading the recovery of a federally listed endangered species. Sierra Nevada bighorn sheep are recolonizing their historic range – with a major assist from CDFW’s twice-yearly captures, collaring and strategic “translocations.”

This spring, three males and four pregnant females were captured from two established herds and translocated to two newly reintroduced herds – one along their western range inside Sequoia National Park and another herd in Inyo County at the southernmost extent of their range.

“Whenever we start these new herds, we like to move a minimum of 20 females as well as additional rams over time,” explained Tom Stephenson, a CDFW senior environmental scientist based in Bishop and the leader of the Sierra Nevada Bighorn Sheep Recovery Program. “At that point, we feel the population has enough animals to begin growing at a high enough rate and also has sufficient genetic diversity.”

Before the animals are relocated, a CDFW team records their vital statistics. Ultrasound machines are used to measure body condition and determine pregnancy status. The animals are outfitted with identifying jewelry – color-coded ear tags, VHF and GPS collars that allow biologists to identify them and track their movements for years in some cases.

All the high-tech, intensive monitoring has paid dividends with new appreciation and understanding. Once believed to always migrate to lower elevations in the winter, CDFW scientists have learned that many sheep ride out the Sierra Nevada’s inhospitable winters at 11,000- to 14,000-foot elevations.

“They are really tough,” Stephenson said. “But they’re able to do that because they put on large amounts of body fat in the summer when they’re on quality habitat. They are essentially hibernating standing up in the alpine. They’ve got an environment up there that is wind-scoured so they can find some food. They’re not having to move around much, and they’re relatively free from predators when they’re up in those altitudes in the winter time.”

Not every sheep captured is relocated.

Helicopter crews this spring attempted unsuccessfully to capture rams in the northernmost part of their range, collar them and return them to their same herds. CDFW biologists are keeping close tabs on the Mount Warren Herd near Lee Vining in Mono County in particular and its proximity to domestic sheep grazing on public land. Sierra Nevada bighorn sheep are disease-free and CDFW biologists want to keep them that way.

While populations have met or exceeded some recovery goals, eliminating disease – or the risk of disease – remains a significant benchmark and key to delisting or down-listing the species from endangered status.<

“There are a lot of bighorn sheep populations throughout the West that continue to struggle with disease,” Stephenson said. “So we’ve worked really hard with public land managers as well as private individuals in the Eastern Sierra to try and ensure our bighorn sheep don’t come into contact with domestic sheep.”

CDFW photos courtesy of Andrew Di Salvo. Top Photo: A helicopter crew delivers four bighorn sheep to CDFW's base camp where vital statistics were recorded, blood was taken, and the sheep were outfitted with identifying ear tags and tracking collars.

As California deer hunters head to the fields, forests and mountains this summer and fall, their experiences will provide wildlife biologists with key data on the health of the state’s deer herds. Wildlife biologists are already seeing the benefits of a 2015 regulation change requiring all deer tag holders to report how they did – successful or not – along with how many days they actually spent hunting, even if they never made it out at all. A record 84 percent of deer tag holders submitted harvest reports for 2016.

“We’re getting more accurate and precise numbers for harvest than we’ve ever had before, which is critical for calculating the tag quota for the next year and conserving our deer populations for the future,” said Stuart Itoga, a senior environmental scientist with CDFW and the state’s deer program coordinator.

Until recently, accurate deer harvest data had proved elusive. Prior to 2015, only successful California deer hunters had to report their take and only about 30 percent of those actually complied. CDFW supplemented the harvest data with numbers collected from game processing facilities, an inefficient process that still left an incomplete picture.

“It’s Wildlife Management 101,” Itoga said. “You have to know what your population is, what’s coming in and what’s going out. We needed to have better numbers.”

Following the mandatory reporting requirement in 2015, submittal rates for deer tag harvest reports jumped to 50 percent. In 2016, a $21.60 non-reporting penalty took effect, which applies to the purchase of future tags, and boosted reporting to the all-time high.

Mandatory deer tag reporting data is just one of a number of new tools that has CDFW deer biologists excited about their ability to better assess California’s deer herds. An innovative DNA study of deer feces promises to give biologists new information about the size and characteristics of the state’s deer population.

CDFW has also greatly expanded the use of deer tracking collars, thanks to improved technology. Since 2016, CDFW has affixed the relatively lightweight, remotely programmable, GPS tracking devices on 350 deer to learn more about their preferred habitat, in-state and out-of-state migration routes and sources of mortality other than hunting. Advanced camera technology also promises to improve the data collected from CDFW’s aerial and ground-based population surveys. A new computer model is being developed to incorporate all of these new data sources into more sophisticated, accurate and precise deer population estimates.

“It’s really an exciting time to be doing this type of work,” Itoga said. “We’ve always used the best available science, but with technology moving at the pace it’s moving now, we have tools available to us now that we didn’t have even five years ago.”

Management changes can happen more quickly as a result. For the upcoming 2017 deer hunting seasons, for example, deer tag quotas were cut in half in three highly desirable, Eastern Sierra X Zones – X9a, X9b and X12 – as a result of new data and field work that showed that migratory deer in these areas suffered from the long, intense winter.

“Winter survival was poor,” Itoga said. “Our hope is that if we reduce the harvest this year, the populations will have a chance to rebound and increase next year.”