Science Spotlight

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.

The latest issue of the scientific journal California Fish and Game is now available online (for free!). Volume 104, Number 1 features a gorgeous photo of a black-tailed jackrabbit in sunlit profile taken by renowned photographer David Jesse McChesney. The back cover image, also by McChesney, features two cottontails at play. We are fortunate to be allowed the use of these amazing images to promote the content of the latest issue. Individual papers in this issue include:

• Reproductive aspects of Sphyraena ensis (Perciformes: Sphyraenidae) inhabiting the coast of San Blas Nayarit, southeast Gulf of California (PDF). The Mexican barracuda is the subject of a study that gathers baseline data for this important fishery resource. Although the species constitutes one of the main economic pursuits along the coast of Nayari, Mexico, little is known about its reproductive biology. A one-year study of specimens caught via commercial fishing revealed that females outnumber males (1:1.87 male:female). They also grow larger—a reproductive strategy that allows them to produce more eggs. By comparing the size of the liver and reproductive organs of the specimens, relative to their overall size, researchers were able to determine that both sexes are at their reproductive peak from April to June. The study results suggest that a fishery closure during this peak reproductive time can provide long-term population benefits for the species.
• Comparison of rabbit abundance survey techniques in arid habitats (PDF). An important component of any species management plan is population data, which is why it is important to know which survey methods are most effective and cost-efficient. Cypher et. al assesses four methods for counting rabbits and hares in arid climates: 1) visual encounter surveys (walking slowly and counting every animal observed); 2) spotlight surveys (driving slowly at night while shining spotlights out each side of the vehicle); 3) aerial surveys (using a low-flying helicopter to flush and count animals along transect routes); and 4) track stations (putting bait in clearings that have been raked smooth, then counting tracks). The results provide interesting observations to consider based upon the individual researcher’s budget, the habitat being studied, and staff time and availability.
• Field method for estimating the weight of tule elk from chest circumference (PDF). Studying larger animals provides an entirely different set of challenges. CDFW biologists frequently capture tule elk for the purpose of relocating them, gathering data and/or providing veterinary care. Administering a proper dose of sedatives and reversal agents is critical for the safety of the animal as well as its human handlers. Since the dosage is based upon weight, the challenge is figuring out how to accurately estimate the weight of an animal that is the size of a full-grown cow. Langner and Casady address this issue by determining a field method for estimating the weight of tule elk. The researchers captured and weighed more than 50 elk over a four-year period, measuring the chest circumference of each animal. The data were analyzed and resulted in a conversion chart that aids researchers in more accurately estimating weights of tule elk in the field.

The latest issue also contains a review of Butch Weckerly’s book, Population ecology of Roosevelt elk: conservation and management in Redwood National and State Parks and a reprint of a scientific paper originally published in 1947 entitled, “Ecology of a cottontail rabbit (Sylvilagus audubonii) population in Central California."

California Fish and Game is CDFW’s official scientific journal devoted to the conservation and understanding of the state’s plants and animals. This issue (either in hi-res or low-res) can be found in its entirety online.

CDFW Photos.

The California Department of Fish and Wildlife (CDFW) has completed its 2018 waterfowl breeding population survey -- and it’s good news for hunters and birdwatchers alike, as the total waterfowl population in the state now tops out at over a half million, for the first time in six years.

Melanie Weaver, who oversees CDFW’s Waterfowl Program, said that duck populations responded positively to the wet winter conditions of 2017. “Given the good upland and wetland habitat conditions last year from excessive precipitation, we anticipated good production,” she said. “We are pleased to see that higher recruitment reflected in this year’s breeding population survey.”

The full Breeding Population Survey Report, which can be found on the CDFW website, indicates the 2018 breeding population of mallards increased from 198,392 in 2017 to 272,859 (an increase of 38 percent). Mallards are the most abundant waterfowl species in the state, followed by gadwall (102,637) and cinnamon teal (78,498).

Other ducks that increased in number include northern shovelers, wood ducks, redhead and canvasback. Overall, the total number of ducks increased from 396,529 to 549,180 (an increase of 39 percent).

A few duck species did decline, including American wigeon, northern pintail, lesser scaup, ring-necked duck, ruddy duck and common merganser. But Weaver gave two possible explanations for these dips. First, none of these species are considered “strong nesters” in California. They migrate through the state, but don’t breed here in high numbers. And second, the survey is designed for dabbling ducks, meaning that diving ducks (such as mergansers) are harder for biologists to detect.

The survey also included Canada geese, which dropped slightly in number, from 55,224 in 2017 to 54,851 this year. (Canada geese are detected and recorded throughout the survey; however, the number reported refers to the traditional nesting population in northeastern California.)

CDFW biologists and warden pilots have conducted this survey annually using fixed-wing aircraft since 1948. The population estimates are for those areas where the vast majority of waterfowl nesting occurs in California, including wetland and agricultural areas in northeastern California, throughout the Central Valley, the Suisun Marsh and some coastal valleys.

In 2018, the survey was flown April 24-28 in the Central Valley and May 9-10 in northeastern California. A few planned survey segments were cancelled due to weather conditions (fog in the Napa-Santa Rosa area, and high winds in a few planned transects in the northeastern part of the state). However, the crew was able to cover 97 percent of the planned survey transects.

The majority of California’s wintering duck population originates from breeding areas surveyed by the U.S. Fish and Wildlife Service (USFWS) in Alaska and Canada. Those survey results should be available in early August. CDFW survey information, along with similar data from other Pacific Flyway states, is used by the USFWS and the Pacific Flyway Council when setting hunting regulations for the Pacific Flyway states, including California.

CDFW Photo

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Media Contacts:
Melanie Weaver, CDFW Wildlife Branch, (916) 445-3717
Kirsten Macintyre, CDFW Communications, (916) 322-8988