Gila River Basin Research Articles

Distribution of a Unique Limpet (Gastropoda: Ancylidae) in the Colorado River Drainage Basin, Western North America

I determined the distribution of limpets (Gastropoda: Ancylidae: Ferrissia) in the Colorado River and Rio Grande basins by handpicking specimens from the undersides of rocks and vegetation at 16 sites from a total of 495 surveyed sites in Colorado, Utah, New Mexico, and Arizona. Shell morphology, including morphometries, was compared to species holotype descriptions and museum lots. Ferrissia rivularis occurred in the upper Colorado, Gunnison, and San Juan rivers, and in the upper Rio Grande basin. Ferrissia walkeri, hereafter called the Walker morph, occurred only in the Gila River basin of Arizona and New Mexico. I reviewed the problems of classification of the Walker morph as being either F. walkeri, described from Arkansas and noted in Michigan and Baja California Sur, or Ferrissia fragilis, described from California and noted from the eastern United States. The Walker morph is identified by its vertical trending protoconch, which lies well within the right posterior quadrant, with the apex of the shell within the posterior third, and the anterior edge of the protoconch lying posterior to and below the apex. The importance of the Gila River Ferrissia population is discussed in reference to the often-proposed paleoaquatic fauna route between the eastern United States and California.

Diet and trophic niche overlap of native and nonnative fishes in the Gila River, USA: implications for native fish conservation

Pilger TJ, Gido KB, Propst DL. Diet and trophic niche overlap of native and nonnative fishes in the Gila River, USA: implications for native fish conservation. Ecology of Freshwater Fish 2010: 19: 300–321. © 2010 John Wiley & Sons A/SAbstract – The upper Gila River basin is one of the few unimpounded drainage basins west of the Continental Divide, and as such is a stronghold for endemic fishes in the region. Nevertheless, multiple nonindigenous fishes potentially threaten the persistence of native fishes, and little is known of the trophic ecology of either native or nonnative fishes in this system. Gut contents and stable isotopes (13C and 15N) were used to identify trophic relationships, trophic niche overlap and evaluate potential interactions among native and nonnative fishes. Both native and nonnative fishes fed across multiple trophic levels. In general, adult native suckers had lower 15N signatures and consumed more algae and detritus than smaller native fish, including juvenile suckers. Adult nonnative smallmouth bass (Micropterus dolomieu), yellow bullhead (Ameiurus natalis) and two species of trout preyed on small‐bodied fishes and predaceous aquatic invertebrates leading to significantly higher trophic positions than small and large‐bodied native fishes. Thus, the presence of these nonnative fishes extended community food‐chain lengths by foraging at higher trophic levels. Although predation on juvenile native fishes might threaten persistence of native fishes, the high degree of omnivory suggests that impacts of nonnative predators may be lessened and dependent on environmental variability.

Local Polynomial–Based Flood Frequency Estimator for Mixed Population

Floods are often generated by more than one physical mechanism, e.g., rainfall and snowmelt. Consequently, traditional flood frequency methods that use a single distribution may not adequately describe the observed flood variability. Mixed distribution models have been proposed but they have two major drawbacks when applied to observed data: (1) determining the appropriate number of components or flood mechanisms and (2) identifying the probability distribution to be used for each component. Further, available flood data are often not sufficient for detecting mixture populations. As a result, mixed-distribution models can be difficult to apply in practice. In this paper we present a nonparametric approach based on local polynomial regression for estimating a flood quantile function that is data driven, flexible, and can capture any arbitrary features present in the data, alleviating the drawbacks of the traditional methods. We applied the proposed method to a suite of synthetic data from mixture of conventional distributions and to flood records that exhibit mixed population characteristics from Gila River basin of southeast and central Arizona. It is found that the proposed method provides a better fit to both the synthetic and historical data. Although the proposed method is presented in the context of mixed population flood frequency estimation, the data-driven nature of the method lends itself as a simple, robust, and attractive alternative to traditional flood frequency estimation.

NATURAL FLOW REGIMES, NONNATIVE FISHES, AND NATIVE FISH PERSISTENCE IN ARID‐LAND RIVER SYSTEMS

Escalating demands for water have led to substantial modifications of river systems in arid regions, which coupled with the widespread invasion of nonnative organisms, have increased the vulnerability of native aquatic species to extirpation. Whereas a number of studies have evaluated the role of modified flow regimes and nonnative species on native aquatic assemblages, few have been conducted where the compounding effects of modified flow regimes and established nonnatives do not confound interpretations, particularly at spatial and temporal scales that are relevant to conservation of species at a range-wide level. By evaluating a 19-year data set across six sites in the relatively unaltered upper Gila River basin, New Mexico, USA, we tested how natural flow regimes and presence of nonnative species affected long-term stability of native fish assemblages. Overall, we found that native fish density was greatest during a wet period at the beginning of our study and declined during a dry period near the end of the study. Nonnative fishes, particularly predators, generally responded in opposite directions to these climatic cycles. Our data suggested that chronic presence of nonnative fishes, coupled with naturally low flows reduced abundance of individual species and compromised persistence of native fish assemblages. We also found that a natural flow regime alone was unlikely to ensure persistence of native fish assemblages. Rather, active management that maintains natural flow regimes while concurrently suppressing or excluding nonnative fishes from remaining native fish strongholds is critical to conservation of native fish assemblages in a system, such as the upper Gila River drainage, with comparatively little anthropogenic modification.

Alluvial chronologies and archaeology of the Gila River drainage basin, Arizona

Late Quaternary alluvial chronologies are established for five streams (Gila River, Salt River, Tonto Creek, Santa Cruz River, and San Pedro River) in the Gila basin of southern Arizona. Each streams has a complex history of deposition, erosion, and landscape stability that structured and fragmented the archaeological record over the last 15,000 years. The limitations that geologic processes imposed on the archaeological record of these alluvial environments must be recognized before meaningful interpretations of prehistory can be made. These stratigraphic sequences also provide the basis for reconstructing changes to the alluvial landscape of each valley over time. All five streams were intensively utilized during the Late Prehistoric period (A.D. 300–1450) by the Hohokam. The Hohokam were irrigation agriculturalists who were dependent upon these streams for survival. Thus, the regional stability and instability of the floodplain environments of southern Arizona influenced the expansion, contraction, reorganization, and collapse of the Hohokam.

Impact of monsoonal rains on spatial scaling patterns in water chemistry of a semiarid river network

The chemical composition of surface waters of nine streams with drainage sizes ranging from 44 to 8900 km2 within a semiarid catchment in the southwestern United States was examined over the monsoonal season of 2006. Primary goals were to determine the impact of monsoonal rains on linkages between landscape cover features and water chemistry in a semiarid river network and to identify whether drainage size influences the temporal variability in water chemistry of streams. Landscape cover features (geology, soil, and vegetation types) were quantified for the subcatchment upstream of each study site and the riparian ecotone. Processes of binary mixing, dilution, and concentration were identified by end member mixing analysis (EMMA). Results showed that most chemical constituents corresponded to geological features at the basin scale, but other constituents (TSS and PO43−) corresponded more closely to riparian features. Importantly, statistical relationships between land cover and water chemistry differed between baseflow and monsoonal conditions, suggesting that seasonal changes in hydrologic routing and water sources (e.g., overland flow versus groundwater sources) have important consequences for stream chemistry. In contrast with mesic drainages, temporal variability in water chemistry increased with spatial scale. The variety of contributing water sources and the relative effect of dilution and concentration in each spatial scale may be underlying processes that explain differences across spatial scales. Observed patterns in the Gila basin suggest that climate variability interacts with hydrologic routing to influence spatial patterns of stream water chemistry in arid basins. Observations made here may be similar to other systems with strongly seasonal climate patterns, and the underlying determinants of stream chemistry change with drainage size.

Tropospheric moisture and monsoonal rainfall over the southwestern United States

This study investigates the role of increased atmospheric humidity in occurrences of wet days in the southwestern United States during the monsoon seasons of 1996–2002, using spatiotemporal analyses of ground‐measured precipitation, spatial analyses of surface and 700‐hPa humidity, and air‐parcel trajectory analyses. A precipitation regionalization indicates that the Gila River basin in southern Arizona/southwest New Mexico should be divided into a western region and an eastern region. A rainfall peak occurred in late August/early September for the western region; however, similar to that of the core monsoon zone in northwestern Mexico, the eastern region of the basin had a rainfall peak in late July/early August. Wet days in the western (eastern) region were associated with a large (moderate) peak in dew point temperature in the southwestern (south central) portion of the basin. The middle troposphere was more humid than normal on both sets of days, with the anomalies for western region wet days being larger and located more over the Gila River basin than anomalies for the eastern region wet days. The Sierra Madre Occidental was the most likely source of middle troposphere moisture for both regions; however, the Gulf of Mexico may have been a significant contributor to rainfall in parts of the eastern region. The Gulf of California probably was the dominant source of low‐level moisture for western region wet days, with gulf surges likely causing the late August/early September peak.

COMPARISON OF GILA TOPMINNOW AND WESTERN MOSQUITOFISH AS BIOLOGICAL CONTROL AGENTS OF MOSQUITOES

I compared acute tolerance of Gila topminnow, Poeciliopsis occidentalis, and western mosquitofish, Gambusia affinis, to ammonia and high water temperature and also compared diet, food selectivity, and impact on invertebrate populations to evaluate the potential for each species to effectively control mosquitoes (Culicidae) in wetland habitats. Critical thermal maxima differed among species, sexes, and lifestages, but these differences were likely not biologically significant due to their small magnitude and the ability of wild populations of both species to adapt to high temperatures. In 24-hour tests, G. affinis displayed about twice the ammonia tolerance as did P. occidentalis. However, long-term survival in habitats with high ammonia concentrations is questionable, thus reducing the perceived benefit of using G. affinis for mosquito abatement in these habitats. Diet overlap was significant between sexes within species but was not significant between species. However, both species exhibited significant dietary selection for mosquito larvae and pupae under experimental conditions. Shared dietary preference for mosquito larvae and pupae, in addition to similarity in temperature tolerance between species, suggests that P. occidentalis, a native and historically widespread species, can be used in place of nonnative G. affinis for mosquito control. There is no evidence to suggest that nonnative G. affinis is better suited for mosquito abatement, and since G. affinis is replacing P. occidentalis throughout the native species' former range, it should no longer be introduced into the Gila River basin for mosquito control. However, managers who would use P. occidentalis for mosquito abatement must take care not to interfere with conservation efforts by disrupting the genetic structure of natural populations of P. occidentalis.

Northward extension of intense monsoonal activity into the southwestern United States

Although it is centered in northwestern Mexico, the Mexican monsoon also has been shown to impact portions of the southwestern United States. To provide more information about the spatial distribution of monsoonal impacts in the Southwest, this study employed multiple linear regression modeling to reduce local topographic impacts on monsoonal precipitation to reveal intense monsoonal activity within the Gila River basin. The precipitation data were daily precipitation totals from 115 stations from June 16–September 15 of 1996–2002. An intense monsoonal zone was found in the south‐central portion of the basin. Therefore, intense monsoonal activity associated with the Sierra Madre Occidental in northwestern Mexico extended into south‐central and southeastern Arizona but not into New Mexico.

Effectiveness of Electrical Fish Barriers Associated with the Central Arizona Project

Abstract The Central Arizona Project (CAP) canal delivers Colorado River water into the Gila River basin. During its planning and construction, issues arose regarding the unwanted entrainment and transport of nonindigenous fishes and other aquatic biota into, through, and out of the canal. One control strategy was the emplacement of electrical fish barriers on two CAP distributary canals to prevent fishes from moving upstream into the Gila River drainage. The operation, maintenance, and effectiveness of these barriers are described for the period 1988–2000. Documented outages totaled more than 100 h, representing less than 0.001% downtime since installation. It is nearly certain that outages allowed immigration by undesired fish(es). Immigrations that occurred when the barriers were operating according to design criteria indicate that the barriers do not totally block the passage of upstream-migrating fish. The proximate sources of electrical barrier outage included component damage from lightning strikes...

Convergence of Differentially Invaded Systems toward Invader-dominance: Time-lagged Invasions as a Predictor in Desert Fish Communities

To what extent do patterns of invasion in one region generalize to other regions? Answering this question is a key goal of invasion biology because it underlies whether we can make progress via comparative studies or must instead cope with a large set of unique cases. Here we quantify similarities and differences in the historical development of nonnative fish assemblages of two North American desert drainages, one with many nonnative fishes (Gila Basin, principally southwestern USA), and one with few (Yaqui Basin, principally northwestern Mexico). The two river basins are similar in size, physiography, and ecology, but because of differences in the timing of regional development, we hypothesized that richness and geographic spread of nonnative fishes in the Yaqui are time-lagged relative to the Gila, and that a slow, but steady increase of nonnative fish occurrence is underway in the Yaqui, similar to what has already occurred in the Gila. Using the comprehensive SONFISHES database, we found that increases in the regional richness of extant nonnative species over time have been roughly linear in both basins. Meanwhile, previously established species have continued to spread spatially, such that the cumulative number of reach records for nonnative species has increased roughly exponentially in both systems. The current status of nonnatives in the Yaqui is remarkably similar to what was evident from the Gila in the past at a comparable level of sampling effort. For all measures of invasion dynamics we examined, a time lag of ∼ 40–50 years exists between the Gila and Yaqui. The majority of extant nonnative fishes are known piscivores, and many have high levels of parental care, a life history trait that affords considerable advantages over native fishes. These results predict that, absent strong action now, the presently abundant native fish fauna of the Yaqui may become increasingly imperiled over the next several years, with a future similar to the Gila, where most native fishes are either extirpated, threatened, or substantially reduced in range, at least partially due to nonnative fishes. We recommend immediate actions to identify and protect high priority portions of the Yaqui Basin from further nonnative fish invasion before further degradation occurs.

NEW AND REDISCOVERED POPULATIONS OF LOACH MINNOW, TIAROGA COBITIS (CY PRINIDAE), IN ARIZONA

Abstract We report collections of threatened loach minnow, Tiaroga cobitis, from 2 Gila River basin (Arizona) streams, one representing a rediscovery and the other a new record. The species had been taken in 1950 from Eagle Creek, but it was not seen again until 1994–1997 and, despite repeated attempts, has not been detected since. It likely persists in adjacent, unsampled areas. A new distribution record is reported for loach minnow captured in 1996 from North Fork of East Fork Black River. This last population has been resampled repeatedly and seems stable. Genetic analysis confirms the uniqueness of these and most other known populations, and we recommend protection and conservation of loach minnow in these 2 streams.

Implications of heterogeneous flood‐frequency distributions on traditional stream‐discharge prediction techniques

AbstractTraditional flood‐frequency analysis involves the assumption of homogeneity of the flood distribution. However, floods are often generated by heterogeneous distributions composed of a mixture of two or more populations. Differences between the populations may be the result of a number of factors, including seasonal variations in the flood‐producing mechanisms, changes in weather patterns resulting from low‐frequency climate shifts and/or El Niño/La Nina oscillations, changes in channel routing owing to the dominance of within‐channel or floodplain flow, and basin variability resulting from changes in antecedent soil moisture. Not recognizing these physical processes in conventional flood‐frequency analysis probably is the main reason that many frequency distributions do not provide an acceptable fit to flood data. In this paper, we use long‐term hydroclimatic records from the Gila River basin of south‐east and central Arizona in the USA to explore the extent and significance of mixed populations. First, we discuss the probable causes of heterogeneity in the frequency distribution of annual flood and present evidence of its occurrence. Second, we investigate the implications of using various popular homogeneous distributions for predicting peak flows for basins that exhibit mixed population characteristics. Third, we demonstrate how alternative frequency models that explicitly account for floods generated by a mixture of two or more populations are both hydrologically and statistically more appropriate. We illustrate how the selection of the most plausible distribution for flood‐frequency analysis also should be based on hydrological reasoning as opposed to the sole application of the traditional statistical goodness‐of‐fit tests. Copyright © 2002 John Wiley & Sons, Ltd.

Effects of Flooding on Recruitment of Roundtail Chub, Gila robusta, in a Southwestern River

Effects of Flooding on Recruitment of Roundtail Chub, Gila robusta, in a Southwestern River

Taxonomy of Chubs (Teleostei, Cyprinidae, GenusGila) in the American Southwest with Comments on Conservation

Abstract Chubs of the Gila River basin have been variously classified as nominal species, subspecies of Gila robusta, or a “complex.” Three full species, robusta, intermedia, and nigra are here recognized, the last possibly arising through more than one hybrization event between robusta and intermedia. Following resolution of a nomenclatural problem, G. nigra is characterized in a key for species identification. Listing under the Endangered Species Act is suggested for all species of Gila in the Colorado River basin.

DID VICARIANCE MOLD PHENOTYPES OF WESTERN NORTH AMERICAN FISHES? EVIDENCE FROM GILA RIVER CYPRINIDS.

Pairwise, two- and three-way Mantel tests were used to evaluate a null hypothesis of no significant covariation when morphological features of three cyprinid fish taxa of the genus Gila were compared. Tests involved ecological conditions and past and present hydrography in the Gila River Basin of western North America. A vicariance hypothesis was the only model statistically proficient in explaining diversity of fish phenotypes. Of paleohydrographic reconstructions compared, those of the mid-Miocene and Pliocene epochs were significantly associated with present-day distributions of phenotypes. Of these, the Pliocene was paramount.

A Case-Control Study of Lung Cancer Mortality in Six Gila Basin, Arizona Smelter Towns

To investigate factors related to lung cancer mortality in six Arizona copper smelter towns, we identified 185 lung cancer cases and two matched controls per case from decedent residents during 1979–1990. Detailed information on lifetime residential, occupational, and smoking history was obtained by structured telephone interviews with knowledgeable informants. Interviews were completed for 82% of 183 eligible cases and 88% of the targeted number (366) of controls. Estimated historical environmental exposures to smelter emissions, based on atmospheric diffusion modeling of measured SO2concentrations, were linked with residential histories to derive individual profiles of residential exposure. Occupational histories were characterized by potential exposure to smelter emissions, asbestos, and ionizing radiation. Conditional logistic regression was used to compare study factors in cases and controls with adjustment for potential confounding factors: gender, Hispanic ethnicity, and smoking. In overall and gender-specific analyses, no statistically significant associations were observed between lung cancer risk and any of the measures of residential exposure to smelter emissions considered (town of residence at time of death, highest level of exposure, and duration or cumulative exposure above background levels), or any of the estimated occupational exposures (definite or potential asbestos, potential ionizing radiation, definite or potential smelter). Among male residents of some, but not all, towns, there was some evidence of a positive association between lung cancer risk and reported copper smelter-related employment (reported as definite), with the highest risk observed for Miami, Arizona. This study provided little evidence of a positive association between lung cancer mortality and residential exposure to smelter emissions. Specific factors associated with the apparent heterogeneity in lung cancer risk across study towns cannot be identified in this community-based study.

Molecular Evidence for a Unique Evolutionary Lineage of Endangered Sonoran Desert Fish (Genus Poeciliopsis)

Efforts to restore an endangered species in its former range should be based on a sound understanding of evolutionary relationships among remaining natural populations. In this study mitochondrial (mt) DNA diversity within and among Gila River drainage populations of the endangered Sonoran topminnow (Poeciliopsis occidentalis) in Arizona was compared to that from neighboring populations in Sonora, Mexico, where the species remains locally abundant. No mtDNA diversity was detected within or among samples from the Gila River basin in Arizona. But considerable variation was found within and among populations from several river systems in Sonora. Examination of mtDNA from a population that inhabits the upper reaches of the Río Yaqui in southeastern Arizona revealed substantial divergence between it and all other populations examined. We comment on the implications of this divergent population for topminnow management in Arizona and argue for more‐detailed genetic and morphological studies to determine the distributional limits and specific status of this highly divergent form.

TREE‐RING RECONSTRUCTION OF UPPER GILA RWER DISCHARGE1

ABSTRACT: Effective planning for use of water resources requires accurate information on hydrologic variability induced by climatic fluctuations. Tree‐ring analysis is one method of extending our knowledge of hydrologic variability beyond the relatively short period covered by gaged streamflow records. In this paper, a network of recently developed tree‐ring chronologies is used to reconstruct annual river discharge in the upper Gila River drainage in southeastern Arizona and southwestern Arizona since A.D. 1663. The need for data on hydrologic variability for this semi‐arid basin is accentuated because water supply is inadequate to meet current demand. A reconstruction based on multiple linear regression (R2=0.66) indicates that 20th century is unusual for clustering of high‐discharge years (early 1900s), severity of multiyear drought (1950s), and amplification of low‐frequency discharge variations. Periods of low discharge recur at irregular intervals averaging about 20 years. Comparison with other tree‐ring reconstructions shows that these low‐flow periods are synchronous from the Gila Basin to the southern part of the Upper Colorado River Basin.

Early Formative Period Chronology for the Tucson Basin

ABSTRACTArchaeological discoveries in the past decade necessitate a reevaluation of views about the Early Formative period (A.D. 1–800) in the Tucson Basin. Traditionally, the local cultural pattern during this period was believed to have been affiliated with the Pioneer period of the Gila Basin Hohokam culture. This viewpoint was formed on the basis of a few decorated Pioneer period ceramics that had been found in the Tucson Basin. Similarities in technological and decorative attributes between these Tucson Basin painted ceramics and their homologues at the site of Snaketown suggested that the cultural developments in the Tucson Basin had been dependent upon the Pioneer period Hohokam cultural pattern. Significant new evidence calls this traditional view into question. A review of this evidence and the chronological outline we develop from it suggests that the Early Formative period in the Tucson Basin predates the appearance of Pioneer period Hohokam in Tucson and is part of a much broader pan-Southwest...