Science Spotlight

Christmas can be the gift that keeps giving -- to anglers and fish alike.

In the north state, CDFW fish habitat technicians oversee the collection of discarded Christmas trees, which will be used to build underwater habitat structures for local waterways. Long after they’ve brightened holiday homes, these trees will provide shelter for juvenile warmwater fish species -- and ultimately will create better fishing opportunities for anglers.

According to Joseph Rightmier, a fish habitat supervisor with CDFW’s Fish Habitat Improvement Shop in Yreka, the trees are weighed down with cables and submerged, creating a refuge for juvenile fish, including Largemouth Bass and crappie.

“The fish get into the voids within the structure, which gives them some protection. And when you attract smaller fish, you also end up attracting larger, catchable fish, which hang out close to the surface and wait for a meal,” Rightmier said.

“Divers have determined that fish start congregating in and around the structures within a day or two of the habitat structures being installed. They’re hot real estate in the water!”

One of the largest efforts to collect and “upcycle” trees is conducted by Rightmier’s team in Siskiyou County. Last summer, staff used trees collected after the 2017 holidays to create and then place 22 habitat structures into Green Springs Reservoir in Modoc County. The habitat structures were comprised of approximately 200 recycled Christmas trees and small junipers. The Christmas trees were collected at drop-off locations in the cities of Alturas and Yreka, and the small junipers were harvested in the Modoc National Forest.

In 2018, Rightmier said, the Yreka fisheries habitat technicians also used trees to build fish habitat structures in three other locations: Juanita Lake, Orr Lake and Trout Lake. Similar projects have also been conducted at Lake Shastina and Dorris reservoir in the past.

Further south, CDFW’s Redding office is also overseeing a Christmas tree collection operation. The tentative collection location will be in the town of Chester, and the trees will be used for a project in Lassen County.

“Generally, we prefer hardwoods when doing habitat projects, but we do use Christmas trees when they’re available,” explained Monty Currier, an environmental scientist with CDFW’s Reservoir Program. “The trees would go a landfill to be chipped otherwise, and we believe that recycling is a better idea. And people are happy to help CDFW with this kind of habitat improvement project – who doesn’t like the idea of making our fisheries better?”

Currier is currently working with a local bass fishing group and county officials to determine a specific tree dropoff point.

Donated trees should not be flocked, and should be stripped of lights, tinsel and ornaments. The trees are usually transformed for their new use within a couple of months, before they dry out completely.

“Our fish habitat shops enjoy doing this type of project, and it makes a real difference in how successful anglers are,” Currier says. “Everybody wins – not just the fish!”

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Interested in recycling your Christmas tree in Siskiyou, Plumas or Modoc counties? Drop-off locations for Christmas trees will be located near the CDFW offices in Alturas (702 East Eighth St.) and Yreka (at the corner of Ranch and Oregon streets, due west of the CDFW yard). In Chester, the location has not yet been determined, but you can call the main office at (530) 225-2300 for information closer to the holiday.

CDFW Photos. All Photos: Fisheries biologists placing recycled Christmas trees into Mountain Meadows Reservoir, Lassen County, to create habitat for juvenile fish.

California Fish and Game, Volume 104, Issue 2, is now available online! California Fish and Game is CDFW's official, quarterly, scientific journal devoted to the conservation and understanding of the flora and fauna of California and surrounding areas, and the eastern Pacific Ocean.

A mallard in flight appears on the cover of the newest installment of the journal. With its iridescent green head and school bus yellow legs, the male mallard is one of the most recognizable species of duck in California. It is also the most abundant breeding species of waterfowl in the state. However, California’s mallard population estimates have generally declined since the mid-1990s. In California mallards: a review, Feldheim et. al synthesizes volumes of research in an effort to identify long-term research needs and monitoring activities to help improve management of this iconic species.

In another paper, entitled Abundance, habitat and occupancy of Roosevelt Elk in the Bald Hills of Redwood National Park, Tolliver and Weckerly seek to understand the relationship between a species’ occupancy-abundance rate and its habitat use. Using elk sign surveys (i.e, counting tracks and feces at standardized locations) researchers found that, as population density increases, Roosevelt elk will move into other (lower quality) habitats. This was true for two herds of vastly different sizes, although the occupancy rate remained comparable.

Finally, Hiney et. al looks at recruiting experienced anglers and using citizen science to help document and survey the native Coastal Rainbow Trout population of Grass Valley Creek Reservoir. The authors look at methods of overcoming the time and resource limitations of assessing wild trout populations.

Also included in this issue are reviews of two books that make meaningful contributions to the field of wildlife research.

As it has for the past 104 years, California Fish and Game continues to publish high-quality, peer-reviewed science that contributes to the understanding and conservation of California’s wildlife. We look forward to witnessing the contributions of the next installment.

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

For more than a century, CDFW’s Trout Hatchery and Stocking Program has been providing recreational fishing opportunities to anglers throughout California. Today, the trout hatchery program is composed of 13 hatcheries, which oversee 20 distinct fish production programs to produce 17 strains, species and subspecies of trout.

McCloud River Redband Trout (Oncorhynchus mykiss stonei) is the latest addition to the CDFW’s production and release efforts. McCloud River Redband Trout is a unique sub-species of rainbow trout endemic to the upper McCloud River area of Shasta and Siskiyou counties of northern California. This fish has beautiful coloration and unique adult characteristics – a pronounced crimson lateral stripe, adult parr marks, relatively large black dorsal spotting, yellow-white hues on the underbelly and white-tipped fins.

The new production and stocking program for McCloud River Redband Trout at Mt. Shasta Fish Hatchery will focus on the upper McCloud River, including McCloud Reservoir. Given that stocking will occur solely within the historic watershed of McCloud River Redband Trout, the program is distinguished by CDFW as a Heritage Trout Production Program. A Heritage Trout is defined as a species of trout native to California, in its native habitat and area. This type of fishery represents the most natural form of aquatic habitat, species and angling opportunity available. Many anglers seeking additional challenges and goals will specifically pursue heritage trout fisheries.

While modern genetics management and conservation hatchery methods are utilized in the McCloud River Redband program, the hatchery-produced fish are primarily for recreational angling and not for release to areas containing wild and genetically pure McCloud River Redband Trout in their natural habitat. This ensures that the most wild populations remain in their native habitat and can continue local adaptation without hatchery influence. CDFW expects the McCloud River Redband Trout program to reach full implementation by 2019-20. The McCloud River Redband program demonstrates CDFW’s progress and commitment to conservation efforts and fisheries management.

CDFW trout hatcheries will continue to produce and stock several strains and species of trout statewide to promote trout angling opportunities, and contribute to the conservation of California’s native species and sub-species of trout. One of the next priorities for the department’s trout hatchery program will commence in 2018, and focus on advancing the Kern River Rainbow Trout program at CDFWs’ Kern River Planting Base.

CDFW Fish and Wildlife Technician Beau Jones stocking McCloud River Redband Trout in August 2017. CDFW photos by hatchery staff.

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.