Status report on the Long-Term Experimental and Management Plan (LTEMP) Metrics for the Glen Canyon Dam adaptive management program
No abstract available.
Arizona, Nevada↗
Geology topics
David Ward
Publications and source records attributed to David Ward.
Evaluating conservation units using network analysis: A sea duck case study
Conserving migratory wildlife requires understanding how groups of individuals interact across seasons and landscapes. Telemetry reveals individual movements at large spatiotemporal scales; however, using movement data to define conservation units requires scaling up from individual movements to species- and community-level patterns. We developed a framework to define flyways and identify important sites from telemetry data and applied it to long-term, range-wide tracking data from three species (640 individuals) of sea ducks: namely, North American scoters ( Melanitta spp). Our network of 88 nodes included both multispecies hotspots and areas uniquely important to individual species. We found limited spatial overlap between scoters wintering on the Atlantic and Pacific coasts of North America, with differing connectivity patterns between coasts. Finally, we identified four multispecies conservation units that did not correspond to traditional management flyways. From this approach, we show how individual movements can be used to quantify range-wide connectivity of migratory species and reveal gaps in conservation strategies.
Frontiers in Ecology and the Environment↗
U.S. Geological Survey Grand Canyon Monitoring and Research Center: Proceedings of the fiscal year 2023 annual reporting meeting to the Glen Canyon Dam Adaptive Management Program
This proceedings is prepared for the USBR and Glen Canyon Dam Adaptive Management Program (GCDAMP) to account for work conducted and products delivered in FY 2023 by SBSC's Grand Canyon Monitoring and Research Center (GCMRC) and to inform the Technical Work Group of science conducted by GCMRC and its cooperators in support of the GCDAMP. It includes a summary of accomplishments, modifications to work plans, and results related to projects included in GCMRC’s FY 2021-23 Triennial Work Plan. This work was done to support the 11 resource goals identified in the Glen Canyon Dam Long-Term Experimental and Management Plan (LTEMP) Environmental Impact Statement and Record of Decision.
Arizona, Nevada, Utah↗
Proceedings of the Fiscal Year 2022 Annual Reporting Meeting to the Glen Canyon Dam Adaptive Management Program
(Hartwell) This report is prepared primarily to account for work conducted and products delivered in FY 2022 by GCMRC and to inform the Technical Work Group of science conducted by GCMRC and its cooperators in support of the Glen Canyon Dam Adaptive Management Program (GCDAMP). It includes a summary of accomplishments, modifications to work plans, results, and recommendations related to projects included in GCMRC’s FY 2021-23 Triennial Work Plan. This work was done to support the 11 resource goals identified in the Glen Canyon Dam Long-Term Experimental and Management Plan (LTEMP) Environmental Impact Statement and Record of Decision (Table 1).
Arizona↗
Comparison of electrofishing and PIT antennas for detection of hatchery-reared Roundtail Chub (Gila robusta) stocked into a desert stream
Stocking of rare native fishes for conservation purposes is a common practice in the southwestern United States. Monitoring typically occurs after hatchery-reared fish are released to assess post-stocking movement and survival. We conducted a two-year study, in which tow-barge electrofishing and portable, flat-bed passive integrated transponder (PIT) antennas were used to monitor PIT-tagged, hatchery-reared roundtail chub ( Gila robusta ) following release into the upper Verde River in Arizona. Specifically, our study aimed to compare the performance of PIT antennas and electrofishing in detecting PIT tagged fish released in a small desert river and to examine the behavioral response of hatchery-reared roundtail chub after stocking. In both years, more fish were detected by antenna arrays (84%) than by electrofishing (30%). roundtail chub were significantly more likely to be detected by antennas than electrofishing each year; however, when antenna data were evaluated only during the few days in which electrofishing took place, there was no significant difference (Year 1, p=0.1784; Year 2, p=0.6295) in detection between gear types for the same time interval, suggesting that electrofishing and antennas are equally likely to detect fish during 48-72 hour time frames. Within 72 hours of release, antennas detected 100% of fish that moved upstream and 93.8% of fish that moved downstream from the stocking location. Overall, less than half (45.6% in Year 1; 41.1% in Year 2) of the stocked roundtail chub were detected using both methods in both years. Utilization of both active capture gear (electrofishing) and passive gear (antennae) had advantages over monitoring with a single method. PIT antennae can be especially useful for managers who lack the personnel or time to implement more intensive methods of capture but want to monitor post-stocking movement and survival of stocked fish.
Arizona↗
What's in the hump of the humpback chub?
The function of the nuchal hump on adult humpback chub ( Gila cypha ) has been the subject of longtime conjecture. Hypotheses about the purpose of the hump range from it being a feature that confers hydrodynamic advantages in swift water to speculation about how the hump may have reduced predation vulnerability to Colorado pikeminnows ( Ptychocheilus lucius ). We used comparative histology of the head region of captive-reared and wild specimens of humpback chub to evaluate whether histological examination could give insight into the function of the hump. Tissues were sectioned, stained, and photographed under a microscope at 2×, 4×, and 40× magnification. The hump is composed almost entirely of skeletal muscle, with little nervous system innervation or fatty tissue. Hump muscle and dorsal muscle appear very similar in terms of muscle cell size, fat content, and connective tissue content. No apparent differences exist between the hump tissues of wild-caught and captive-reared individuals. Histological analysis and study of the anatomical structure of the head through dissection, along with evidence from other species, suggest that the hump evolved to reduce predation vulnerability. Although the reason for the evolution of the hump in humpback chub remains uncertain, additional information about the composition of the hump can help to support or refute hypotheses related to its function.
Western North American Naturalist↗
Geographic variation in the intensity of warming and phenological mismatch between Arctic shorebirds and invertebrates
Responses to climate change can vary across functional groups and trophic levels, leading to a temporal decoupling of trophic interactions or ‘phenological mismatches.’ Despite a growing number of single-species studies that identified phenological mismatches as a nearly universal consequence of climate change, we have a limited understanding of the spatial variation in the intensity of this phenomenon nor what influences this variation. In this study, we tested for geographic patterns in phenological mismatches between six species of shorebirds and their invertebrate prey at ten sites spread across ~13º latitude and ~84º longitude in the Arctic over three years. At each site, we quantified the phenological mismatch between shorebirds and their invertebrate prey at: 1) an individual nest level, as the difference in days between the seasonal peak in food and the peak demand by chicks, and 2) a population level, as the overlapped area under fitted curves for total daily biomass of invertebrates and dates of the peak demand by chicks. We tested whether the intensity of past climatic change observed at each site corresponded with the extent of phenological mismatch and used Structural Equation Modeling to test for causal relationships among: 1) environmental factors, including geographic location and current climatic conditions, 2) the timing of invertebrate emergence and the breeding phenology of shorebirds, and 3) the phenological mismatch between the two trophic levels. The extent of phenological mismatch varied more among different sites than among different species within each site. A greater extent of phenological mismatch at both the individual-nest and population-levels coincided with changes in the timing of snowmelt as well as the potential dissociation of long-term snow phenology from changes in temperature. The timing of snowmelt also affected the shape of the food and demand curves, which determined the extent of phenological mismatch at the population level. Finally, we found larger mismatches at more easterly longitudes, which may be affecting the population dynamics of shorebirds, as two of our study species show regional population declines in only the eastern part of their range. This suggests that phenological mismatches may be resulting in demographic consequences for arctic-nesting birds.
Alaska↗
Viability of Razorback-Flannelmouth Sucker hybrids
Razorback sucker ( Xyrauchen texanus ) and flannelmouth sucker ( Catostomus latipinnis ) live in sympatry in the Colorado River basin. Although morphological intermediates have been described since 1889, hybrids were seemingly rare. Rarity of hybrids was likely attributed to razorback suckers' ability to find conspecific mates throughout the basin. Dams have segmented the Colorado River, altering habitat and isolating native fish populations. As a result, razorback suckers became endangered. Razorback suckers are uncommon in the Colorado River and hybridization could increase because of limited conspecific mates. To understand the impacts of hybridization on recovery of the razorback sucker, information on hybrid viability is needed. We compared hatch success and larval survival of artificially spawned razorback sucker, flannelmouth sucker, and their hybrids. We were able to successfully spawn and rear all combinations, implying that there are limited pre- and postzygotic isolation mechanisms, and hybrids are likely to survive in the wild.
Arizona, Baja California, California, Colorado, Ne↗
Effects of high flow experiments on warm-water native and nonnative fishes
The harsh environmental conditions and extreme flooding that created Grand Canyon also shaped the unique native fish that evolved in the Colorado River. Native fish have evolved their physiology, morphology and behavior to withstand high flood events. Flooding has been shown to benefit spawning, survival and recruitment of juvenile native fishes in many southwestern rivers. Annual pre-dam flooding on the Colorado River was sometimes more than double the flows released during a typical High-Flow Experiment (HFE). It is therefore unlikely that the 3-4 days of high flow created by HFEs will have negative impacts on native fish directly. However, HFEs can cause dispersal of flood adapted non-native species like green sunfish that utilize floods to invade and colonize new environments. Continued efforts to reduce known populations of green sunfish that inhabit backwater ponds before conducting HFEs may be necessary to reduce risks of spreading invasive green sunfish downstream.
Arizona↗
Change in dominance determines herbivore effects on plant biodiversity
Herbivores alter plant biodiversity (species richness) in many of the world’s ecosystems, but the magnitude and the direction of herbivore effects on biodiversity vary widely within and among ecosystems. One current theory predicts that herbivores enhance plant biodiversity at high productivity but have the opposite effect at low productivity. Yet, empirical support for the importance of site productivity as a mediator of these herbivore impacts is equivocal. Here, we synthesize data from 252 large-herbivore exclusion studies, spanning a 20-fold range in site productivity, to test an alternative hypothesis—that herbivore-induced changes in the competitive environment determine the response of plant biodiversity to herbivory irrespective of productivity. Under this hypothesis, when herbivores reduce the abundance (biomass, cover) of dominant species (for example, because the dominant plant is palatable), additional resources become available to support new species, thereby increasing biodiversity. By contrast, if herbivores promote high dominance by increasing the abundance of herbivory-resistant, unpalatable species, then resource availability for other species decreases reducing biodiversity. We show that herbivore-induced change in dominance, independent of site productivity or precipitation (a proxy for productivity), is the best predictor of herbivore effects on biodiversity in grassland and savannah sites. Given that most herbaceous ecosystems are dominated by one or a few species, altering the competitive environment via herbivores or by other means may be an effective strategy for conserving biodiversity in grasslands and savannahs globally.
Nature Ecology & Evolution↗
Effectiveness of ultrasonic imaging for evaluating presence and maturity of eggs in fishes in remote field locations
Ultrasonic imaging is an effective, nonlethal method used to determine sex and maturity in a variety of fishes. However, many previous studies of this technique have been performed in laboratory environments. Using Common Carp Cyprinus carpio , we developed a standardized method for ultrasonically scanning cyprinids, and we accurately sexed 78% ( N = 58) of those individuals. We then applied this method to endangered Humpback Chub Gila cypha and obtained 751 scans of Humpback Chub in remote field locations within the Grand Canyon, Arizona. Ultrasonic scanning took less than 1 min per fish to perform, and we identified females containing eggs based on two jpeg images and one 10-s video clip. Using ImageJ software to evaluate ultrasonic scans of ovulatory, captive Humpback Chub, we determined that female fish were potentially ovulatory when scanned eggs exhibited an ImageJ brightness value within the range of 32–44. Although we could successfully evaluate egg maturity, we were unable to estimate egg mass. Fisheries managers can use this noninvasive scanning method or a similar technique in remote field locations to collect ultrasonic scans from cyprinids to determine their reproductive status.
North American Journal of Fisheries Management↗
Abundance trends and status of the Little Colorado River population of humpback chub
The abundance of the Little Colorado River population of federally listed humpback chub Gila cypha in Grand Canyon has been monitored since the late 1980s by means of catch rate indices and capture-recapture-based abundance estimators. Analyses of data from all sources using various methods are consistent and indicate that the adult population has declined since monitoring began. Intensive tagging led to a high proportion (>80%) of the adult population being marked by the mid-1990s. Analysis of these data using both closed and open abundance estimation models yields results that agree with catch rate indices about the extent of the decline. Survival rates for age-2 and older fish are age dependent but apparently not time dependent. Back-calculation of recruitment using the apparent 1990s population age structure implies periods of higher recruitment in the late 1970s to early 1980s than is now the case. Our analyses indicate that the U.S. Fish and Wildlife Service recovery criterion of stable abundance is not being met for this population. Also, there is a critical need to develop new abundance indexing and tagging methods so that early, reliable, and rapid estimates of humpback chub recruitment can be obtained to evaluate population responses to management actions designed to facilitate the restoration of Colorado River native fish communities. ?? Copyright by the American Fisheries Society 2006.
North American Journal of Fisheries Management↗