Science Spotlight

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  • March 5, 2020

A wild turkey inside a cardboard box to keep it calm is weighed as CDFW Environmental Scientist Laura Cockrell records the data at the Upper Butte Basin Wildlife Area.
Environmental Scientist Laura Cockrell records the weight of a wild turkey at Little Dry Creek prior to banding.

A banded wild turkey’s two legs show off the two different type of bands CDFW biologists affix to the birds at the Upper Butte Basin Wildlife Area. One band is riveted closed; the other clamped close until its two butt-ends are touching.
Wild turkeys banded in 2019 and 2020 are given one traditional, butt-end band on one leg and one rivet band on the other.

Silvery metallic butt-end bands in the hand of CDFW environmental scientist Laura Cockrell.
Environmental Scientist Laura Cockrell shows off the supply of butt-end bands prior to banding.

Turkey hunters in parts of Butte and Glenn counties who are skilled and lucky enough to bag a tom this spring may be in for a pleasant surprise: Their bird may be sporting some jewelry – a band on each leg.

Since early February, CDFW biologists at the Upper Butte Basin Wildlife Area – supported by the National Wild Turkey Federation (NWTF) – have been busy trapping and double-banding wild turkeys at the wildlife area’s Howard Slough and Little Dry Creek units. So far this year, some 45 turkeys have been banded, which include toms, hens and young males known as “jakes.”

The staff and volunteers have just about a month and a half to trap and band all the wild turkeys they can between the close of the waterfowl hunting season and the start of the spring wild turkey season in mid-March. It’s part of an innovative research effort aimed at better understanding the characteristics, growth rates, habitat use, range and abundance of the growing population of wild turkeys using the wildlife area.

Bird bands long have been an important research tool for biologists and considered a prize among many hunters who are allowed to keep them after reporting the band information. The Upper Butte Basin turkey banding project is the only one of its kind in the state, making those turkey bands a rare commodity and a valuable potential data source.

In addition to the banding, the turkeys are weighed, sexed and measured at various points before being released.

The wild turkey study began at the wildlife area in 2015 along with the launch of limited spring wild turkey hunts there. NWTF helped secure grant funding to start the hunt program and initiate the research effort. The funds came from the sale of upland game bird hunting validations and stamps required of upland game bird hunters.

“We thought it would be great to start getting an abundance estimate for the turkeys that we do have out here to make sure that we weren’t harming the population through the hunt program and also to see how much hunter opportunity we could potentially utilize,” said Kevin Vella, NWTF’s district biologist for California, Nevada, Oregon and Washington.

The spring wild turkey hunt program has been so successful and popular over its short history funding for the program and its research component will continue under CDFW’s general budget moving forward.

“I think Howard Slough especially offers some of the best turkey hunting I’ve seen anywhere,” said Upper Butte Basin Wildlife Area Manager Tim Hermansen. “Certainly, youth hunters have an excellent opportunity out here.”

Spring turkey hunts at both the Howard Slough and Little Dry Creek units are limited to lottery drawings through CDFW’s website in order to ensure an uncrowded, high-quality hunting experience. The hunter quota and the turkey harvest both have grown over the years along with the local turkey population. Hunter success ranged from 30 to 60 percent during the 2019 spring season but reached 100 percent for the youth hunt at Howard Slough in 2018.

Back to those double-banded birds.

Although 101 turkeys were banded at the wildlife area between 2015 and 2019, only three banded turkeys have been reported by hunters. That leads biologists to believe most of the turkeys have been prying off the traditional, “butt-end” bird bands, which have two edges that butt evenly together when clamped on.

The NWTF has since supplied Upper Butte Basin with rivet bands that are made of a harder metal and riveted closed when attached. The turkeys banded in 2019 and 2020 now receive a butt-end bird band on one leg and a rivet band on the other. Any of those harvested birds wearing a single rivet band will confirm suspicions that the birds have been prying off the butt-end bands.

“That’s the downside of doing any kind of novel research,” explained Laura Cockrell, a CDFW environmental scientist based at the Upper Butte Basin. “You only have your own mistakes to learn from.”

CDFW Photos. Top Photo: Upper Butte Basin Wildlife Area Manager Tim Hermansen releases a wild turkey after banding as Fish and Wildlife Technician Derek Schiewek and Seasonal Aid John Davis look on.

Media Contact:
Peter Tira, CDFW Communications, (916) 322-8908

Categories: General
  • January 29, 2020

map featuring locations of bird surveys throughout Northern California in a region representing more than 40 percent of all California’s coniferous forests.
Locations of bird surveys throughout Northern California in a region representing more than 40 percent of all California’s coniferous forests. CDFW has been monitoring wildlife at these locations since 2002 to help inform conservation efforts. Photo courtesy of Dr. Brett Furnas.


automated sound recorder used to survey songbirds. An automated sound recorder used to survey songbirds. These devices were programmed to make three 5-minute recordings before, at, and after sunrise –repeated over three consecutive mornings. The timing of the recordings is significant because different species tend to sing at different times in the morning. Photo courtesy of Dr. Brett Furnas.

New research shows climate change may harm migratory songbirds. Saving their forest habitat may help.

Songbirds that travel to northern California each summer from winter ranges in Central and South America appear to be more sensitive to climate change than other types of songbirds, according to new research by CDFW Wildlife Ecologist Dr. Brett Furnas.

In a new paper published in the journal Biological Conservation, Dr. Furnas analyzes 14 years of data taken from the surveys of songbirds living in northern California conifer forests. The bird surveys were done in the Klamath Mountains, Southern Cascades and North Coast Ranges, a region representing 42 percent of all conifer forests in the state.

“The data is especially significant because it is representative of such a large region,” said Dr. Furnas.

Research was completed using automated sound recorders which captured the calls of songbirds at over 1,000 sites between 2002 and 2016. Birds were surveyed at their annual summer breeding grounds about a month after arriving from their winter homes.

Dr. Furnas studied three types of songbirds: year-round residents; short-distance, altitudinal migrants which winter at lower elevations and breed at higher-elevations; and long-distance, Neotropical migrants that winter in Mexico, Central America and South America and breed in California.

“The research alone is an amazing part of this story. Each of the 1,000-plus survey sites required someone to drive to the middle of the forest, hike for an hour or more and install survey equipment,” said Dr. Furnas.

The data shows that Neotropical migrant songbirds are shifting their summer ranges to higher elevations where the climate is cooler. But there’s a downside to the new migration pattern: The long journey reduces the Neotropicals’ flexibility when it comes to breeding behavior. Adjusting to changes in temperature and available food resources in California ultimately hurts their reproductive success.

“Neotropicals’ sensitivity to climate change makes them a conservation risk. It’s unclear if they can adapt as climate continues to warm,” said Dr. Furnas.

There was less evidence of elevational shifting for resident and altitudinal songbirds, indicating they might not be as vulnerable to increases in temperature. This is likely because species that migrate shorter distances – or don’t migrate at all – have more time to prepare for the breeding season. They also have more time to establish a territory, sing to attract a mate and gather food to help raise a brood.

The Neotropicals’ vulnerability is exacerbated by other factors as well. One consequence of the compressed breeding cycle is that the birds can’t afford to tone down singing on hot days when it becomes metabolically taxing. In contrast, resident birds tend to sing less on hot days.

Dr. Furnas sees conservation of mid-elevation conifer forests as part of the solution. Neotropicals are expanding their range to about 5,000 feet and above.

“Middle-elevation conifer forests appear to have features of natural climate refugia. Conserving these forests is crucial,” he said.

However, the natural climate refugia identified by Dr. Furnas have their own vulnerabilities. “If you think of mountains like a triangle, there’s less land area in the middle-elevation forests that Neotropicals are shifting to than in the lower elevation forests they’re abandoning. The availability of forest habitats at higher elevations could be limited in the future due to faster rates of warming at those elevations,” Dr. Furnas said.

For these reasons, the middle zone is a sweet spot for birds. “An increasing number of birds will be crowding into this sanctuary,” he said.

Dr. Furnas’ ultimate message is that research with an emphasis on biodiversity monitoring will be essential to future conservation efforts. Research based on biodiversity monitoring can help identify species and habitats that are most in need of conservation. It can also help conservationists and policy makers assess the effectiveness of conservation actions.

Read Dr. Furnas’ paper: link opens in new windowRapid and Varied Responses of Songbirds of Climate Change in California Coniferous Forests

CDFW Photos. Top Photo: Long-distance Neotropical migrants like the Hermit Thrush may be more vulnerable to climate change than other types of songbirds.

Media Contact:
Ken Paglia, CDFW Communications, (916) 322-8958

Categories: General
  • October 30, 2019

Image of a healthy steelhead trout being measured and surveyed in 2017.
A healthy steelhead trout surveyed at Pescadero Creek Lagoon Complex in 2017

Dozens of dead steelhead trout are pictured following a turbulent wintertime breach of the lagoon in 2014.
The aftermath of a winter sandbar breach 2014. These nearly annual breaches resulted in large die-offs for the lagoon’s steelhead.

Wide shot of a manual sandbar breach between the lagoon and ocean. Scientists manually breach the lagoon to prevent fish deaths caused by the nearly annual wintertime sandbar breaches.
A manual breach of Pescadero Creek Lagoon Complex. Managed breaches of the lagoon can prevent fish kills caused by turbulent natural breaches. Photo Courtesy of UC Davis School of Veterinary Medicine

There’s a dichotomy in the way Pescadero Creek Lagoon Complex in coastal San Mateo County has both supported—and been detrimental to—steelhead trout for much of the past 25 years.

On one hand, the lagoon complex—the largest tidal marsh between Elkhorn Slough and the San Francisco Bay estuary—boasts high growth rates for Central California Coast Steelhead. The lagoon system allows the species, which is federally listed as endangered, to reach a size that increases their likelihood of surviving at sea. Steelhead also use the system for juvenile rearing and resting during migration.

On the other hand, nearly every year since the mid-1990s, the lagoon faced harsh fall/winter sandbar breaches that filled the system with oxygen-depleted water and spread toxic sediment produced by the breakdown of organic matter like plant material in the absence of oxygen.

These breaches often resulted in large die-offs for the lagoon’s steelhead population. Historically, population estimates have reached as many as 17,000 steelhead rearing into the fall.

“It was a one-two punch where fish faced lack of oxygen and got hit with harsh toxic compounds. It was really unfortunate because the lagoon system works so well to grow steelhead, but we were losing the production every year,” said District Fisheries Biologist Jon Jankovitz.

Efforts to actively manage breaches began in 2012, but were stalled in 2014 and 2015 when the steelhead population was diminished due to drought conditions. In 2015, the California Department of Fish and Wildlife (CDFW) and the National Oceanic Atmospheric Administration (NOAA) partnered with the Department of Parks and Recreation (DPR), which owns much of the land associated with the complex, in adopting a monitoring and management plan.

In 2016, a significant fish kill caused by a turbulent sandbar breach prompted further action. CDFW, NOAA and DPR resumed active management to improve water conditions and prevent the deadly breaches.

The restoration team installed a sandbar dam at a major channel to slow the release of oxygen-depleted water and sediment into the system. Staff also preemptively manually breached the lagoon mouth on occasions when they anticipated a harmful natural breach.

Jankovitz conducts weekly water quality monitoring and twice-monthly dry-season fish sampling to inform management decisions. He produces an annual report on the health of the steelhead population and a summary of seasonal water quality transitions.

So how has active management faired? There hasn’t been a significant fish kill since 2016.

“We’ve saved the steelhead population for the last couple of years. We’re fortunate for the success we’ve had so far,” said Jankovitz.

Another mark of success has been the documented presence this year of sexually mature holdovers, meaning steelhead that were reared in the lagoon for two seasons even though they were large enough to smolt (i.e. migrate to sea).

“This obviously couldn’t happen if there was a fish kill the year prior. These holdovers represent a life history strategy that may fill in gaps during down reproductive years or periods of poor ocean conditions,” said Jankovitz.

There’s a long-term restoration plan in the works which would likely involve structural changes, such as relocating culverts and breaching levees, to alter the dynamics of how much tide flows in and out of the system. The plan includes a sediment removal project that was implemented in 2019 to increase fish passage.

Ultimately, CDFW and DPR would like to keep the system thriving without active management. “We don’t love breaching the lagoon manually because it can be stressful for fish and other aquatic species,” Jankovitz said.

Meanwhile, fostering an environment in Pescadero Creek Lagoon Complex that supports a large population of fast-growing steelhead continues to be top priority.

“Aside from being a native California species with a long history of recreational and angler use, steelhead are a great biological indicator of the health of streams and lagoon systems. The ecology of these systems would likely fall apart without them,” Jankovitz said.

Photos courtesy of CDFW District Fisheries Biologist Jon Jankovitz and the Bodega Marine Lab at University of California, Davis. Top Photo: District Fisheries Biologist Jon Jankovitz with a healthy Pescadero juvenile steelhead.

Media Contact:
Ken Paglia, CDFW Communications, (916) 322-8958

Categories: General
  • September 11, 2019

Black and white image of a man crouched in front of truck, holding a large fish in one hand and measuring stick in other hand. Man is wearing plaid collared shirt and pants.
Faded black and white photos are all that’s left of the Owens River Gorge’s glory days as a trophy brown trout fishery. Biologists expect the fish to make a comeback following near-annual pulse flows that begin in September to improve habitat.

Sepia colored image of young man and older man sitting behind table covered in nearly 100 fish. A sign in front reads Harry Smith, 23 years 1953 74 browns, from the owens river gorge, limit 25 trout per day.

Two men in waders standing in river. One man has a large machine backpack on and holds a long, yellow stick in the water. Other man holds a net. Rocks and rough river in background.
CDFW crews electrofish the Owens River Gorge two times per year to assess the health of the river’s brown trout.

From boom to bust to decades of angler indifference, few California fisheries have experienced such wild swings of fortune as Mono County’s Owens River Gorge.

The latest chapter in the long saga of the Gorge unfolds this month when the Los Angeles Department of Water and Power (LADWP) sends a relatively brief burst of water known as a “Channel Maintenance Flow” down the 10-mile stretch of river between the Upper Gorge Power Plant and Pleasant Valley Reservoir to benefit fish habitat.

From Sept. 9 to Sept. 17, water flows will rise from the relatively placid 35 to 55 cubic feet per second (cfs) typical in the Gorge to 680 cfs before gradually ramping back down. link opens in new tab or windowAccess to the Gorge will be closed by LADWP during the nine-day “pulse flow” event for public safety.

The temporary boost in water flow represents the successful resolution of decades of legal battles involving LADWP, Mono County and CDFW. The high flows are expected to breathe new life into the Owens River Gorge ecosystem and its once-storied brown trout fishery. Court settlements mandate the pulse flows continue almost annually -- 18 out of every 20 years.

The flows are intended to replicate seasonal scouring that occurred naturally in the Gorge long before dams, power plants and water diversions were constructed in the last century. In fact, these alterations dried up the Owens River Gorge from 1953 to 1991 until years of litigation restored some minimal flows and attempts to restart a once-fabled brown trout fishery.

The Owens River Gorge is paradoxical – so close yet so far away. Just northwest of Bishop and within sight of Highway 395, it is difficult to access with limited and steep trails to reach its waters 500 to 900 feet below the rim. Since water returned to the Owens River Gorge in 1991, it has been more popular with hikers and rock climbers than trout anglers.

It was a much different story prior to the construction of the Long Valley Dam in 1941, which created Crowley Lake, and the subsequent addition of a number of power plants along the stretch of river. Before then, the Owens River Gorge was a destination brown trout fishery with a worldwide reputation. So good was the fishing it was one of the few waters in California with limits based on weight – 25 pounds plus one fish per angler per day.

CDFW Environmental Scientist Nick Buckmaster is based in Bishop and conducts twice-yearly electrofishing surveys in the Gorge along with macroinvertebrate sampling.
“Right now, the fish populations are pretty stunted,” Buckmaster said. “We just don’t have large brown trout in the Gorge anymore.”"

The Gorge is home almost exclusively to wild brown trout and the populations are high. Buckmaster estimates between 1,500 to 5,000 trout per mile, numbers that compare favorably to many blue-ribbon trout fisheries in the state.

“The problem is they are all small. Their growth really slows down around 5 inches, and most of the fish in the Gorge are less than 8-inches long. Their growth really plateaus,” he said. “By the time they get to 8 inches, they are geriatric fish.”

Buckmaster explained that brown trout undergo an important life change once they reach between 8 and 14 inches in size. They mostly stop eating aquatic insects and transition into apex predators, preying on other fish and just about anything else of substance they can eat. The diet change leads to rapid growth and turns them into a prize for any trout angler skilled enough to catch them.

Plateauing at 5 inches, however, most of the brown trout in the Owens River Gorge never reach that important developmental milestone or achieve it only toward the end of their lives.

“If you want big brown trout, they need something to eat,” Buckmaster said. “And they usually need a lot of something to eat.”

CDFW fisheries biologists expect the pulse flows to provide just that by dramatically altering the ecosystem. The big burst of water will scour pools and restore the deep-water holding and ambush habitat needed by large brown trout. The flows will flush out years of accumulated sediment, exposing gravel beds critical for trout breeding while fostering a broader diversity of aquatic life than what’s present in the Gorge today.

Mayflies and stoneflies are largely absent from the ecosystem, and caddisflies – safely encased and underneath rocks in their larval stages – provide a limited food source. Small populations of native Owens suckers exist in the Gorge. Their numbers are expected to grow with an increase in aquatic insect life following the pulse flows, incidentally providing important forage for growing brown trout.

The high waters will inundate and benefit riverside riparian growth, offering shade and cover and additional insect habitat. The flows also are expected to flush out invasive  New Zealand mud snails that have infested the Gorge over time. The snails provide little benefit to fish and are a source of competition for other macroinvertebrate life.

Buckmaster said biologists could see positive changes in the Gorge as quickly as three months after the flows. And bigger brown trout could start turning up in Buckmaster’s electrofishing surveys – and at the end of anglers’ lines – as early as next year.

CDFW Photos. Top Photo: CDFW scientific aids Christi Kruse and Emma Hewitt identify some of the macroinvertebrate life taken from the Owens River Gorge.

Categories: General
  • August 2, 2019

Creek running through hilly, riparian habitat filled with trees and bushes.
Rock Creek, where Shasta Crayfish were released by hand July 15.

Bucket filled with small crayfish.
Shasta Crayfish await delivery into their new home in Rock Creek. The Shasta Crayfish is a small- to medium-sized crayfish found only in northeast California.

White bucket with several crayfish.
Establishing populations of Shasta Crayfish in suitable water bodies that are inaccessible to invasive crayfish is the central effort in conserving the species.

Closeup of white bucket with several crayfish.
The mix of 28 Shasta Crayfish introduced into Rock Creek included both juveniles and adults of varying sizes.

A 20-year, multiagency effort to find a safe haven for California’s only remaining native crayfish culminated recently with the release of 28 Shasta Crayfish (Pacifastacus fortis) into a restored section of Rock Creek in Shasta County.

The Shasta Crayfish has been in decline and under assault for decades from the pervasive, nonnative, invasive Signal Crayfish (Pacifastacus leniusculus), which not only outcompetes it for food and habitat but renders Shasta Crayfish females largely infertile through interbreeding. Found only in northeastern California, the Shasta Crayfish was listed as an endangered species by both the state and federal governments in 1988.

It was all smiles and optimism for a brighter future July 15, however, with the release of the 28 adult and juvenile Shasta Crayfish into a formerly dry, meadow portion of Rock Creek on property owned by Pacific Gas and Electric Company. That portion of Rock Creek, just six-tenths of a mile long, now flows with a reliable supply of cool, clear water with habitat enhancements that include rock clusters and riparian plantings.

Restoration of Rock Creek was completed in 2016 through a partnership with PG&E, CDFW, the U.S. Fish and Wildlife Service and the biological consulting firm Spring Rivers Ecological Sciences LLC.

Spring Rivers scuba divers collected Shasta Crayfish from the bottom of nearby Crystal Lake in June. Crystal Lake is believed to hold the most genetically robust population of Shasta Crayfish left in the wild but a population that’s also in decline as a result of the invading Signal Crayfish. The Shasta Crayfish were quarantined for 42 days before release into their new home.

Key to the Shasta Crayfish’s recovery as well as its biggest obstacle is establishing populations in waters inaccessible to the invasive Signal Crayfish. The refuge at Rock Creek was 20 years in the making by the time the site was identified, project proposals prepared and approved, permits secured, partnerships formalized, restoration work completed and the Shasta Crayfish translocated last month.

Restoration of the creek involved major construction removing a diversion dam upstream and rerouting a pipeline that supplied CDFW’s Crystal Lake Hatchery with water downstream. The location was deemed ideal as CDFW’s fish hatchery would block any Signal Crayfish in Crystal Lake from moving up into the restored portion of the creek.

In their new Rock Creek refuge, the Shasta Crayfish will be closely monitored. The hope is that they can serve as a sustainable, genetically diverse source population for future introductions.

CDFW Photos. Top Photo: Divers carefully released Shasta Crayfish by hand into their new home July 15. Prior to release, biologists measured and recorded their size and other data.

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Media Contact:
Peter Tira, CDFW Communications, (916) 322-8908

Categories: General