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Geology topics

G.A. Mueller

Publications and source records attributed to G.A. Mueller.

9 recordsLinked to original sources
USGS2008

Small nonnative fishes as predators of larval razorback suckers

The razorback sucker (Xyrauchen texanus), an endangered big-river fish of the Colorado River basin, has demonstrated no sustainable recruitment in 4 decades, despite presence of spawning adults and larvae. Lack of adequate recruitment has been attributed to several factors, including predation by nonnative fishes. Substantial funding and effort has been expended on mechanically removing nonnative game fishes, typically targeting large predators. As a result, abundance of larger predators has declined, but the abundance of small nonnative fishes has increased in some areas. We conducted laboratory experiments to determine if small nonnative fishes would consume larval razorback suckers. We tested adults of three small species (threadfin shad, Dorosoma petenense; red shiner, Cyprinella lutrensis; fathead minnow, Pimephales promelas) and juveniles of six larger species (common carp, Cyprinus carpio; yellow bullhead, Ameiurus natalis; channel catfish, Ictalurus punctatus; rainbow trout, Oncorhynchus mykiss; green sunfish, Lepomis cyanellus; bluegill, L. macrochirus). These nonnative fishes span a broad ecological range and are abundant within the historical range of the razorback sucker. All nine species fed on larval razorback suckers (total length, 9-16 mm). Our results suggest that predation by small nonnative fishes could be responsible for limiting recovery of this endangered species.

Southwestern Naturalist↗
USGS2007

Communication using eye roll reflective signalling

Body reflections in the ultraviolet (UV) are a common occurrence in nature. Despite the abundance of such signals and the presence of UV cones in the retinas of many vertebrates, the function of UV cones in the majority of taxa remains unclear. Here, we report on an unusual communication system in the razorback sucker, Xyrauchen texanus, that involves flash signals produced by quick eye rolls. Behavioural experiments and field observations indicate that this form of communication is used to signal territorial presence between males. The flash signal shows highest contrast in the UV region of fhe visual spectrum (??max???380 nm), corresponding to the maximum wavelength of absorption of the UV cone mechanism in suckers. Furthermore, these cones are restricted to the dorsal retina of the animal and the upwelling light background is such that their relative sensitivity would be enhanced by chromatic adaptation of the other cone mechanisms. Thus, the UV cones in the sucker have optimal characteristics (both in terms of absorbance and retinal topography) to constitute the main detectors of the flash signal. Our findings provide the first ecological evidence for restricted distribution of UV cones in the retina of a vertebrate. ?? 2007 The Royal Society.

Proceedings of the Royal Society B: Biological Sci↗
USGS2006

Bullfrog tadpole (Rana catesbeiana) and red swamp crayfish (Procambarus clarkii) predation on early life stages of endangered razorback sucker (Xyrauchen texanus)

Bullfrog tadpoles (Rana catesbeiana) and red swamp crayfish (Procambarus clarkii) are widespread introduced taxa that are problematic throughout the western United States. Their impact on native amphibians and crustaceans is well documented, but less is known regarding their influence on native fishes. Predator-prey tank tests showed both species consumed eggs and larvae of the endangered razorback sucker (Xyrauchen texanus) in a laboratory setting. Tadpoles consumed 2.2 razorback sucker eggs/d and 1.4 razorback sucker larvae/d, while crayfish ate 6.0 eggs/d and 3.5 larvae/d. Relatively high densities of bullfrog tadpoles and crayfish in razorback sucker spawning areas suggest that these nonnative taxa might pose a threat to the recruitment success of this and other imperiled native fish.

Southwestern Naturalist↗
USGS2005

A legacy of change: The lower Colorado River, Arizona-California-Nevada, USA, and Sonora-Baja California Norte, Mexico

The lower Colorado is among the most regulated rivers in the world. It ranks as the fifth largest river in volume in the coterminous United States, but its flow is fully allocated and no longer reaches the sea. Lower basin reservoirs flood nearly one third of the river channel and store 2 years of annual flow. Diverted water irrigates 1.5 million ha of cropland and provides water for industry and domestic use by 22 million people in the southwestern United States and northern Mexico. The native fish community of the lower Colorado River was among the most unique in the world, and the main stem was home to nine freshwater species, all of which were endemic to the basin. Today, five are extirpated, seven are federally endangered, and three are being reintroduced through stocking. Decline of the native fauna is attributed to predation by nonnative fishes and physical habitat degradation. Nearly 80 alien species have been introduced, and more than 20 now are common. These nonnative species thrived in modified habitats, where they largely eliminated the native kinds. As a result, the lower Colorado River has the dubious distinction of being among the few major rivers of the world with an entirely introduced fish fauna. ?? 2005 by the American Fisheries Society.

American Fisheries Society Symposium↗
USGS2004

Reintroduction of the flannelmouth sucker in the lower Colorado River

A single stocking of 611 wild flannelmouth suckers Catostomus latipinnis in 1976 represented the first successful reintroduction of a native fish in the lower Colorado River. Flannelmouth suckers ranging in age from young of the year to 24 years were captured during 1999–2001; their population was estimated as at least 2,286 (95% confidence interval, 1,847–2,998). Recruitment appeared sporadic, consisting of consecutive years of low recruitment (<10%) supplemented by a stronger (31%) year-class. Historically, this native fish was rare and was believed extirpated from the lower river by 1975, but it now reproduces naturally in a reach dramatically altered by water development. This successful reintroduction indicates that one native fish can successfully tolerate environmental alterations whereas another, the razorback sucker Xyrauchen texanus , apparently cannot. Other opportunities may exist in altered rivers to benefit native fishes where they were absent or historically rare.

North American Journal of Fisheries Management↗
USGS2004

Collection of an adult gizzard shad (Dorosoma cepedianum) from the San Juan River, Utah

We collected an adult gizzard shad ( Dorosoma cepedianum ) from the San Juan River just upstream of Lake Powell, Utah, on 6 June 2000. This represents the first documented occurrence of the species in the Colorado River or its tributaries. The adult male (35 cm TL, 470 g) was taken by trammel net from a small (0.5 ha), shallow (<2 m) backwater along with several other fish that included 3 endangered razorback sucker ( Xyrauchen texanus ). The specimen is stored at the Museum of Southwestern Biology, University of New Mexico, Albuquerque (curation number 49122).

Western North American Naturalist↗
USGS2004

Distribution and abundance of pelagic fish in Lake Powell, Utah, and Lake Mead, Arizona-Nevada

Pelagic fish communities (waters with depths >20 m) of Lakes Powell and Mead were examined quarterly from 1995 to 1998 using vertical gill nets and a scientific echosounder. Nets captured a total of 449 fish consisting of striped bass (57%/45% [Lake Powell/Lake Mead]), threadfin shad (24%/50%), common carp (15%/4%), walleye (3%), channel catfish (2%), and rainbow trout (<1%). Each reservoir contained concentrations of pelagic species separated by expanses of habitat with few fish (<10 kg·ha⁻¹). Reservoirs experienced dramatic seasonal and annual fluctuations in pelagic biomass. Lake Powell's biomass peaked at the Colorado River at 709.7 (± 46.5) kg · ha⁻¹ and Lake Mead's reached 291.9 (± 58.2) kg · ha⁻¹ at Las Vegas Wash. These locations supported estimated fish densities of 124,668 fish · ha⁻¹ and 15,131 fish · ha⁻¹, respectively. Maximum reservoir biomass peaked in August 1996, with Lake Powell supporting 10,852,738 ± 5,195,556 kg (27.6 × 10⁻ fish) and Lake Mead 1,926,697 ± 892.994 kg (10.8 × 10⁻ fish). Biomass ebbed in May (1996 and 1997), when Lake Mead supported 65% (296,736 kg vs. 453,097 kg) and 62% (101,016 kg vs. 162,262 kg) of biomass levels found in Lake Powell.

Arizona, Nevada, Utah↗
USGS2000

Distribution, movements, and habitat use of razorback sucker (Xyrauchen texanus) in a lower Colorado River Reservoir, Arizona-Nevada

Distribution, movements, and habitat use of 10 wild adult razorback suckers ( Xyrauchen texanus ) were examined in Lake Mohave, Arizona-Nevada, from November 1994 through July 1997. Movement rates (0.00-17.35 km d⁻¹) and ranges (x̄ = 39 km) were similar to those for riverine populations. All study fish returned to spawning sites used in previous years, but they also visited other spawning areas. Spawning females were significantly (P = 0.031) more active than males (480 vs. 87 m d⁻¹) and moved substantial distances between spawning sites during peak reproduction (1-28 February). Fish became most active (m d⁻¹, km month⁻¹) after spawning and moved to areas known to support higher algal production. Fish were typically within 50 m (F < 0.001) of shore and at average depths between 3.1 and 16.8 m (range 0.2 to > 30.0 m). Adults were detected throughout the available thermal gradient (12°-30°C), but during summer typically had body temperatures between 18° and 22°C. Vertical movements within the water column showed no correlation with depth or time of day, but seasonal shifts suggest fish may regulate body temperature by seeking specific temperatures during reservoir stratification.

Arizona, Nevada↗