Relative growth and body condition of the Finescale Triggerfish (Balistes polylepis) were evaluated using fishery-dependent data from the southeastern Gulf of California across eight sampling periods between 2002 and 2024. Growth consistently showed a negative allometric pattern, with marked ontogenetic shifts occurring within a narrow size range closely associated with sexual maturity and likely changes in habitat use. These growth transitions indicate reallocation of energy from somatic development toward reproduction. The condition factor varied significantly among periods but generally remained close to unity, indicating good overall physiological status of the population. Although lower condition values coincided with the extreme El Niño event of 2015–2016, the association between climatic anomalies and body condition was not statistically significant, suggesting broad resilience to regular environmental variability and potential sensitivity only during extreme events. These results highlight the importance of accounting for ontogenetic growth shifts when assessing population dynamics and provide ecological insight relevant for the management of this exploited species.
Continued cases of lead poisoning among California condors (Gymnogyps californianus), after California laws began requiring the use of non-lead ammunition when shooting wildlife, has hunters, conservationists, and lawmakers searching for answers. Researchers maintain that lead poisoning remains the greatest threat to the recovery of California condors (Rideout et al. 2012; Finkelstein et al. 2012; Bakker et al. 2024) and have identified the ingestion of lead from spent ammunition as the primary source for these scavengers (Church et al. 2006). In a central California condor population ranging from southern Santa Clara County to San Luis Obispo County, we documented 25 condor fatalities due to lead toxicosis in 2020–2024, or an average of 5% annual mortality due to lead during that five-year period (USFWS 2024). This regularity of fatalities due to lead exposure seemed unlikely when the Ridley-Tree Condor Preservation Act was approved in 2007, requiring the use of non-lead ammunition within the condor range of California. The law was extended statewide in 2019 and required non-lead ammunition for shooting any wildlife species with any firearm in the state. Nevertheless, the lead threat remains for scavengers. Continued lead poisoning of condors has some wondering if lead ammunition is still being used, despite the law, and what else needs to be done to solve the lead poisoning problem.
Large whales seasonally aggregate into highly productive areas to feed, which often overlap with regions popular for various fishing activities. This spatial and temporal overlap can lead to whale entanglements in fishing gear. Along the California coast, such impacts have been amplified by intense marine heat waves and climate-driven shifts in whale migration and habitat use, resulting in unprecedented reports of entangled whales and substantial disruptions to the region’s valuable Dungeness crab fishery. In response, the Risk Assessment and Mitigation Program (RAMP) was established to reduce entanglement risk through collaboration and adaptive management. As part of this program, we sought to quantify the spatial footprint of crabbing effort in California waters. To achieve this, we analyzed solar logger positional data collected from a sample of commercial crabbing vessels in Central and Northern California, applying movement models adapted from animal behavior studies to identify where crabbing occurred. We then fitted resource selection functions using environmental and operational variables predicted to influence crab fishing behavior, producing a spatial surface of crabbing probability. This information on the timing and location of crabbing activity enhances our understanding of fishing effort distribution and enables managers to implement targeted strategies that, when combined with whale distribution data, may reduce entanglement risk while maintaining optimal crabbing opportunities.
We examined the population ecology of western Joshua trees (Yucca brevifolia) in the Antelope Valley of the western Mojave Desert, California. The western Joshua tree is an iconic species of the Mojave Desert and a species of conservation concern in California. The Antelope Valley supports extensive, unstudied stands of Joshua tree, which are biogeographically unique and morphologically distinct from other stands across its range. In this region, largely clonal stands of western Joshua tree occur at the western leading edge of its range, where the Mojave Desert meets the Tehachapi Mountains, southern Sierra Nevada, and Transverse Ranges. Climate regimes here differ markedly from those in the rest of the range. Patchily distributed stands of dense, short-statured Joshua tree stems dominate our study area on the bajadas, washes, and canyons of the Tehachapi Mountains. The proportion of stems representing unique genets remains unclear. From 2010 to 2023, a span of 13 years, we monitored growth rates and changes of number of apical growth points of several hundred individually marked Joshua tree stems within 23 plots. Stem densities of clonal populations were an order of magnitude higher than the maximum densities reported from non-clonal populations. The high survival and growth rates of these stems were comparable to rates reported in other parts of its range, but height and number of branches are lower than in non-clonal populations. While fire is considered to play a driving role in the development of the clonal growth form, we documented significant rhizomatous stem production and high rates of height and branch regression in the absence of fire. We hypothesize that stem height and branch regression in this landscape are due to damage from high winds, which may also play a role in shaping stand architecture by pruning stems. In Joshua tree stands subject to significant wind damage, estimating age from stem height and mean growth rates become more uncertain. Production and survival of clonal stems is dynamic, and stem densities and stand architecture can change rapidly.
The Marine Life Management Act (MLMA), California Fish and Game Code, sections 7050–7090, requires an ecosystem-based approach for managing the state’s fisheries, using the best available science, and involving stakeholders in a comprehensive and transparent process. The 2018 MLMA Master Plan for Fisheries (Master Plan) provides guidance and methods for implementing MLMA goals and objectives and is the California Department of Fish and Wildlife’s (CDFW) document for managing state finfish, invertebrate, and algal commercial and recreational fisheries. The California Halibut Trawl Grounds (CHTG), created through legislation (1971), provides trawl fishermen access to a section of state waters off Santa Barbara and Ventura counties to target California halibut (Paralichthys californicus). Legislation (Fish & G. Code, § 8495) requires the California Fish and Game Commission (CFGC) to evaluate trawl gear effects on specific Performance Criteria every three years. The CFGC is required to close any area within the CHTG where trawl gear does not meet the required criteria. The last evaluation of the CHTG occurred in 2008, with the CFGC closing one area due to the presence of hard bottom habitat and least fiscal impact to the fishing fleet. From 2022–2023, we re-assessed these Performance Criteria by incorporating recent catch disposition data, West Coast Groundfish Observer Program data, current biogeographical data, and relevant scientific literature. We assessed 2,152 individual organisms, representing 55 species, with 77.9% released live. No species of concern were caught, and minimal bottom contact was evident. We identified management control measures which protect distinct aspects of ecosystem function. Spatial analysis using GIS compared kelp, hard bottom, and biogenic habitats against trawl locations which showed no overlap. Our findings suggest that light touch trawl gear in the CHTG fishery meets the Performance Criteria in Fish and Game Code, section 8495. These findings suggest that additional closures within the CHTG are not currently warranted.
A key aspect related to successful hemp cultivation is an understanding of the physiological performance of hemp and how differing cultivars and genotypes respond physiologically to cultivation practices and environmental stressors. In this study, we examine the leaf-level physiological response of two hemp cultivars (“Boax” and “Cherry-Wine”) across the growing season from late vegetative phase to late flowering, with a specific focus on leaf-level gas exchange, photosynthetic capacity, and cannabinoid content. We observed similar and high photosynthetic capacity for the hemp cultivars in our study during late vegetative and early to mid-flowering phases of crop development. Prior to harvest, we observed a seasonal decline in leaf physiological function and photosynthetic capacity in late flowering for both cultivars, and we conclude that a reduction in photosynthetic capacity along with the onset of plant senescence explains much of the reduced physiological performance that we observed as hemp matured into late flower. Plastic mulching cover over planting rows had no significant effect on leaf physiological function or final cannabidiol (CBD) content, and we attribute this lack of any treatment effect to the fact that plastic mulch cover did not significantly affect canopy microclimate, nor did it significantly affect plant-available soil water in any physiological impactful manner. The Boax and Cherry-Wine cultivars exhibit high physiological performance in relation to photosynthetic capacity and a correspondingly high CBD content; however, despite the inherent productivity of these two cultivars, growers should be cautious when utilizing these hemp cultivars given their potential to exceed tetrahydrocannabinol (THC%) regulatory thresholds during compliance testing.
Unmanned aerial vehicles (UAV), often referred to as unmanned aerial systems (UAS) or drones, are experiencing increasing use by wildlife researchers and for a variety of purposes. When equipped with one or more of the various sensors currently available, these remotely operated platforms are being used to conduct aerial surveys of large mammals occupying a diversity of ecosystems, but more so for species that occupy terrain that is neither as rugged nor topographically extreme as that occupied by mountain sheep. Despite some of the potential advantages offered by this technology, UAVs have not been used extensively to survey populations of mountain sheep. In this paper, we provide some background information regarding the (1) utility of these platforms to survey mountain sheep; (2) types of unmanned aerial vehicles currently available; (3) types and limitations of currently available sensors; (4) factors that complicate use of these technologies specifically for surveys of mountain sheep populations; and (5) some additional suggestions, including ways to mitigate some of those complications. For reasons enumerated herein, these aerial platforms and associated sensors currently are used sparingly in mountain sheep habitat, but we predict use will increase substantially as a result of technological advances and the human safety advantages associated with these devices.
The immense ecological plasticity of coyotes (Canis latrans) facilitates their use of anthropogenically altered habitats including urban areas. We analyzed scat samples to compare food item use by coyotes in urban, peri-urban, and non-urban zones in and around the city of Bakersfield, California. Coyotes consumed primarily rabbits and rodents in all three zones although species composition varied among the zones. Other important foods included birds and invertebrates in the urban zone, commercial grapes in the peri-urban zone, and birds and fruits in the non-urban zone. Frequency of occurrence of anthropogenic items was not statistically different between zones but exhibited an increasing trend from the non-urban zone to the urban zone. However, coyotes in the urban zone do not appear to be dependent on these items. The relatively low use of anthropogenic foods may reduce the potential for human-coyote conflicts in Bakersfield.
Minerals are important nutrients and are essential components of the diets of animals. Nutritional requirements or minimum concentrations of minerals for nutritional health are largely unknown for the majority of large, free-ranging herbivores. We investigated concentrations of 9 trace minerals in mule deer (Odocoileus hemionus) inhabiting 3 distinct geographic areas—Cima Dome, New York Mountains, and the Mid Hills—in the eastern Mojave Desert, San Bernardino Co., California from 2008 to 2016. These areas differed in vegetative communities, topography, water availability, and fire histories. Telemetered mule deer demonstrated high fidelity to each of these areas, and movement by those individuals between study areas was not detected. During our investigation, overall differences occurred in mean concentrations of magnesium (P < 0.001), calcium (P = 0.022), phosphorus (P = 0.023), potassium (P = 0.042), and selenium (P < 0.001) among the 3 geographic areas. Among years, differences occurred in concentrations of the trace elements investigated in the New York Mountains with the exceptions of magnesium and potassium; at Cima Dome with the exceptions of iron, sodium, potassium, and selenium; and in the Mid Hills with the exceptions of magnesium and zinc. A positive upward trend existed between selenium concentration in the New York Mountains and the year of sample collection (P < 0.05), and a similar—albeit not significant—upward trend was discernible in the Mid Hills, but no such relationship was apparent at Cima Dome. These results emphasize the importance of investigating micronutrient status of mule deer on a local scale and temporally and add to the sparse information available on trace mineral concentrations in mule deer. Despite limited samples (≤165), we make available for the first time reference values for mule deer inhabiting the Mojave Desert, to serve as a baseline against which to measure responses to future environmental perturbations or for comparison with deer occupying other disparate ecosystems, and further contribute to the derivation of reference values for mule deer in general.
Effective survey methods to detect small mammal species are often needed to develop conservation and management plans in forested ecosystems. The ability to use non-invasive methods to identify small mammal species in the field is particularly useful as live trapping can be time consuming and potentially harmful to the study species. We tested a camera trap method in a coastal redwood (Sequoia sempervirens) forest for small mammals, originally designed by Gracanin et al. (2019) and called the “selfie trap”, that uses a camera trap with a modified lens in a baited PVC tube. We determined if we could use this camera trap set-up on the ground to accurately identify small mammals to species to assess species diversity in a forested ecosystem as well as if it could withstand disturbance from larger mammals (e.g., bears). We surveyed for small mammals in areas of old-growth and second-growth coastal redwood forests in northwestern California. We detected 10 small mammal species and were able to identify most individuals to species including squirrel, chipmunk, mice, woodrat, shrew, vole and mole species. This camera trap set up also detected approximately 77% of small mammal species known to potentially occur in the area. Moreover, although larger mammals could interact with the camera trap set up, their disturbance was limited to when they were interacting with the trap, and the bait and camera set-up remained functional for subsequent small mammal detections. Thus, this method could be used instead of live trapping in complex forested ecosystems to effectively determine small mammal species presence, diversity, and activity levels, avoiding disturbance from large mammals.
Field surveys and sentinel studies were conducted with juvenile Chinook salmon (Oncorhynchus tshawytscha) in the Sacramento River between 2012 and 2022. Both Ceratonova shasta and Parvicapsula minibicornis were common myxozoan parasites of both juvenile and adult Chinook salmon. C. shasta infection was found to be associated with morbidity and clinical disease among sampled juvenile salmon in multiple years. This finding demonstrates that disease is another adverse survival factor for juvenile salmon in the Sacramento River. In 2016 and 2018, river water was assayed for C. shasta spore concentration with peak values occurring near Red Bluff Diversion Dam. In some years, C. shasta may reduce juvenile salmon survival. Monitoring water-borne spore stages and salmon infection would inform how flow management influences the parasite lifecycle in the Sacramento River.
