Science Spotlight

In the heart of California’s Sacramento-San Joaquin River Delta lies a 3,000-acre flooded island called Franks Tract.

Before humans diked and drained Franks Tract to grow potatoes, grains, asparagus and corn, the island was part of a vast freshwater marsh. Breaches in levees flooded Franks Tract in 1937, and farmers never reclaimed the island. Franks Tract today is a nexus point of many delta uses, ranging from duck hunting and bass fishing to fresh water supply for California cities and farms.

But the island is also a hot spot for invasive plants and predatory fishes, as well as a conduit for saltwater intrusion into waterways used to convey freshwater supplies to cities and agriculture in the Delta and other parts of California. For these reasons, Franks Tract is considered a strong candidate for partial restoration.

“Franks Tract is a microcosm of many of the larger problems pervading the inner Delta, said Carl Wilcox, Delta policy advisor to the director of the California Department of Fish and Wildlife. “Some native fishes are in serious decline, improving the quality of available habitat in the Delta and increasing resilience to drought and climate change could support their persistence and recovery.”

Various partners, led by CDFW, are proposing to restore about 1,000 acres of Franks Tract to tidal marsh. The proposed restoration is consistent with the Delta Smelt Resiliency Strategy, state goals for the Franks Tract State Recreation Area, and state water quality control plans for the San Francisco Estuary. The effort also aligns with the multi-agency Delta Conservation Framework and the Central Delta Corridor Partnership.

The proposed restoration could shrink waterweeds, grow fish food, create habitat for Delta smelt and other declining species, and prevent salinity intrusion into the south Delta. It may also improve recreational opportunities for residents and visitors.

Results of hydrodynamics modeling indicate the proposed restoration would provide more fresh water to the central Delta shielding regions upstream from ocean saltwater intrusion. A 2017 UC Davis survey documented year-round use of Franks Tract and surrounding channels by locals, visitors and researchers, and seasonal use by hunters, anglers and boaters. Many survey respondents were concerned about changes in access to the water and effects on the local economy and sport fishing, which is dependent on that access. The survey yielded useful information for the next, more detailed, planning and design round including a locally proposed alternative design.

“We will continue to work with stakeholders to not only address habitat and water quality priorities, but also enhance recreational and sport fishing opportunities,” Wilcox said.

A recently released report, Franks Tract Futures: Exploring Options for Multi-Benefit Restoration and Increased Resilience in the Central Delta Corridor, summarizes the technical studies and stakeholder input that’s been collected relative to the potential restoration of Franks Tract.

If approved for further development, the Franks Tract restoration proposal would enter a second phase of planning, design and environmental review with a target end date of December 2020.

CDFW Photos.

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.

WARC diver Shelby Kawana assesses habitat at one of the CDFW red abalone stocking sites located off the coast of southern California.


WARC diver Armand Barilotti assesses habitat at one of the CDFW red abalone stocking sites located off the coast of southern California.


Octopus are a top abalone predator and therefor pose a threat to newly stocked juvenile red abalone populations. Researchers catch and relocate octopus when they are found hiding in crevasses near stocking sites.


A rediscovered stocked red abalone was found clinging to the underside of a rock during a one year post stocking survey.

Harvesting abalone for dinner used to be as fundamental to a Southern California lifestyle as fish tacos and flip-flops. But by 1998, a combination of overfishing and disease led to the closure of all abalone fishery south of San Francisco. By 2001, the white abalone was listed as an endangered species because populations continued to decline despite protection from fishing pressure. Population numbers are so low today that the only option for recovery is believed to be through a robust captive breeding and stocking program.

Scientists from the California Department of Fish and Wildlife (CDFW) White Abalone Recovery Project and their partners in the White Abalone Recovery Consortium (WARC) are working to bring back the iconic white abalone from the brink of extinction. Since 2016, CDFW and partners have been working to actively restore abalone populations through stocking of young captive-reared abalone. Successful stocking is the critical next step to reestablishing self-sustaining wild populations of this culturally and ecologically important mollusk. The early stocking studies have aimed to perfect the methods that will be used to restore wild white abalone populations in the future by using red abalone as a test case. Red abalone, a sister species of the white abalone, lives in the same deep kelp forest habitats, and their populations in Southern California have also been very slow to recover.

Every few months, scientific divers on board the CDFW research vessel Garibaldi wrestle into thick neoprene wetsuits and load heavy steel tanks onto their backs in order to check on the stocked abalone. As the divers descend deeper into the kelp forest, they enter the world of the white abalone. Sunlight streams through the towering giant kelp, briefly illuminating the shiny sides of the small fish taking cover in the kelp blades. Lobsters and octopuses are tucked into the crevices of rocks, and abalone and urchins shelter in the shadows. Many of those abalone are adorned with small brightly-colored numbered tags that identify them as the new additions to the neighborhood. After a few months in the wild, the stocked abalone can show an extensive amount of growth which speaks to the quality and abundance of resources in their new habitat.

Since restoration stocking began in 2016, the partnership has stocked close to 10,000 red abalone off the coast of southern California. These studies are helping scientists understand how stocked abalone interact with their new environment in the wild. Researchers are increasing the effectiveness of future stocking work by teasing out the risk factors that abalone face in their new environment. For multiple years after releasing the abalone, divers track the number and identity of each abalone, and assess the ecosystem health and predator abundances at each site. The divers also collect any abalone shells encountered to determine the effects of different predators at each site through time.

Octopuses, lobsters, sea stars and fish are all major predators of the young abalone, and care is taken to introduce the abalone during times of the year when the predators will be least abundant. All of the data from these early studies are aimed at lessening the risks that stocked abalone face, and to improve long-term growth and survival.

The WARC understands that abalone are at the heart of coastal California’s identity and culture. The return of red and white abalone to the wild marks the beginning of a new chapter in the love story between California and this amazing mollusk. This is true for the ecosystems that rely on them as well as for the humans that cherish them. Please stay tuned for updates on the lessons learned from these studies, and plans for upcoming white abalone stocking work!

For more information, please visit the following pages:

• UC Davis Bodega Marine Laboratory’s White Abalone Captive Breeding Program
• Journal of Shellfish Research, Vol. 35, No. 3: “Implementing a Restoration Program for the Endangered White Abalone (Haliotis Sorenseni) in California”

CDFW Photos. Top Photo: Newly tagged red abalone that are ready to be released into the ocean during a WARC stocking study in 2016.

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.

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.