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Floodplains are presumed to be important rearing habitat for the endangered razorback sucker (Xyrauchen texanus). To help recover this endemic Colorado River Basin species, the Upper Colorado River Endangered Fish Recovery Program implemented a floodplain acquisition and enhancement program. Levee removal was initiated in 1996 as one component of this floodplain restoration program. The goal of the Levee Removal Study was to evaluate the system responses to levee removal and make specific recommendations concerning the value of floodplain/river reconnecting for endangered species (specifically razorback sucker) recovery.
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 (x?= 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...
Four groups of larval razorback sucker, an endangered fish, were exposed to selenium-laden zooplankton and survival, growth, and whole-body residues were measured. Studies were conducted with 5, 10, 24, and 28-day-old larvae fed zooplankton collected from six sites adjacent to the Green River, Utah. Water where zooplankton were collected had selenium concentrations ranging from <0.4 to 78 microg/L, and concentrations in zooplankton ranged from 2.3 to 91 microg/g dry weight. Static renewal tests were conducted for 20 to 25 days using reference water with selenium concentrations of <1.1 microg/L. In all studies, 80-100% mortality occurred in 15-20 days. In the 28-day-old larvae, fish weight was significantly reduced...
This report represents a river reach application of the reset concept to examine survival and growth of larval razorback sucker and bonytail in floodplains. The floodplain reset concept refers to eliminating residual fish populations from floodplains prior to their connection to the river during spring flood flows. Despite drought conditions, sufficient river flows allowed the evaluation of the reset concept to enhance larval razorback sucker Xyrauchen texanus and bonytail Gila elegans survival during 2003-2004. Species composition in study floodplains shifted from communities dominated by riverine species to to those preferring lentic conditions following recruitment within floodplains. The number, biomass, and...
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Populations of the endangered razorback sucker (Xyrauchen texanus) in the middle Green River have declined since closure of Flaming Gorge Dam in 1962. The apparent cause for the decline is a lack of successful recruitment. Recruitment failure has been attributed to habitat alteration and competition and predation by exotic fishes on early life stages of razorback sucker. This study was conducted to evaluate two of the potential reproductive bottlenecks that might limit recruitment of razorback sucker in the Green River Drainage; (1) reduced larvae production due to sediment deposition on spawning areas, and (2) reduced survival of larvae or juveniles due to lack of timely access to food-rich backwater and floodplain...
We evaluated the role of major tributary streams for endangered fish recovery using a matrix approach based on quantitative information. However, the need for ranking tributaries for direct and indirect contributions (i.e., assignment of high, medium or low importance) required a more subjective approach. Some streams differed in actual and potential importance because barriers deny fish access to suitable habitat. We have not assigned relative importance to the different types of contributions; to a large extent that may involve policy issues better addressed by the Recovery Program.
nthropogenic selenium contamination of aquatic ecosystems was first associated with cooling reservoirs of coal-fired power plants in the late 1970s, and later with drainage water from agricultural irrigation activities in the 1980s. In the 1990s, selenium contamination has been raised as a concern in the recovery of currently endangered fish in the Colorado River system. Widespread contamination from seleniferous drain waters from agriculture has been documented in the upper and lower Colorado River basins. Historically, irrigation started in the upper Colorado River basin in the late 1880s. In the 1930s, selenium concentrations in various drains, tributaries, and major rivers in the upper and lower Colorado River...
Adult razorback sucker (Xyrauchen texanus) were exposed to various selenium concentrations in ponds and isolated river channels of the Colorado River near Grand Junction, CO, to determine effects on their growth and residue accumulation over an 11-month period. Adults at Horsethief ponds were fed a commercial diet, whereas fish at Adobe Creek channel and North Pond foraged on natural food items. Selenium concentrations at Horsethief were 2.2 microg/L in water, 0.1-1.4 microg/g in sediment, and 2.3-3.1 microg/g in food organisms (1.1 microg/g in commercial fish food), at Adobe Creek were 3.8 microg/L in water, 0.5-2.1 microg/g in sediment, and 4-56 microg/g in food organisms, and at North Pond were 9.5 microg/L in...
The razorback sucker (Xyrauchen texanus) is listed as federally endangered throughout its range. A massive recovery effort by the Recovery Implementation Program for Endangered Fish Species in the Upper Colorado River Basin has focused its efforts in the upper Colorado River. The upper Colorado River basin also has two locations that have been identified by the National Irrigation Water Quality Program as having substantial selenium contamination. Selenium is toxic to fishes, affecting reproductive success. Thus, there is concern about potential effects of selenium on the endangered razorback sucker. Two sets of studies have investigated the effects of selenium on razorback suckers, but study results are conflicting....
Razorback sucker (Xyrauchen texanus) larvae from adults exposed to selenium at three sites near Grand Junction, Colorado, for 9 months were used in a 30-day waterborne and dietary selenium study. Selenium concentrations in water averaged <1.6 microg/L from 24-Road, 0.9 microg/L from Horsethief, 5.5 microg/L from Adobe Creek, and 10.7 microg/L from the North Pond. Selenium in dietary items averaged 2.7 microg/g in brine shrimp, 5.6 microg/g in zooplankton from Horsethief east wetland, 20 microg/g in zooplankton from Adobe Creek, and 39 microg/g in zooplankton from North Pond. The lowest survival occurred in larvae fed zooplankton rather than brine shrimp. Survival of larvae at Adobe Creek and North Pond was lower...
Seventeen subadult, hatchery-reared razorback suckers (Xyrauchen texanus; (x? = 456 mm total length) were implanted with sonic transmitters and tracked for 23 months in the lower 89.6 km of the San Juan River (San Juan arm of Lake Powell, Utah). Fish were released at 2 sites, and 9 made extensive up- and downstream movements (x? = 47.8 km; contact was lost with 4, and 4 others presumably died or lost their transmitters). The San Juan arm is primarily inundated canyon; however, most fish contacts occurred in shallow coves and shoreline with thick stands of flooded salt cedar in the upper inflow area. Eight fish frequented the Piute Farms river/lake mixing zone, and at least 4 moved upstream into the San Juan River....
Despite successful reproduction by razorback suckers (Xyrauchen texanus) in the middle Green River, recruitment beyond the larval stage has not been recently observed. Bonytail (Gila elegans) are essentially extirpated in the wild and nearly all bonytail present in the Green River are hatchery-stocked fish. Floodplain wetlands may provide important rearing habitat for both larval razorback sucker and bonytail. However, survival of razorback suckers in restored floodplain habitat has not been observed since 1997, even when larvae were introduced directly into floodplain sites. Large nonnative fish populations in floodplain habitats have likely suppressed survival. The recent drought eliminated, or reset, nonnative...
Juvenile razorback sucker (Xyrauchen texanus) in a managed wetland adjacent to the Green River, credited to Modde, Timothy, published in 1996. Published in Western North American Naturalist, volume 56, issue 4, on pages 375 - 376, in 1996.
The upper Colorado River basin, which is composed of the Colorado River and its tributaries upstream of Lake Powell, is home to 14 native fish species, four of which are now endangered. These four fish  the Colorado pikeminnow (Ptychocheilus lucius), razorback sucker (Xyrauchen taxanus), bonytail (Gila elegans) and humpback chub (Gila cypha evolved in the Colorado River basin and exist nowhere else on earth (www.r6.fws.gov/coloradoriver). The Dolores River is a significant tributary to the Colorado River and thus the status if its native fish community is of keen interest to state and federal agencies that manage native fish.
Floodplain restoration is an important element of the Upper Colorado River Endangered Fish Recovery Program. Floodplain restoration was initiated in 1996 by lowering natural and manmade levees that were preventing natural floodplain function by limiting the frequency and duration of river-floodplain connection.
Elevated selenium concentrations documented in water, sediment, and biota in irrigation drain water studies by U.S. Department of the Interior agencies and academia have raised concerns that selenium may be adversely affecting endangered fish in the upper Colorado River basin. The objective of the study was to determine the effects on endangered razorback sucker (Xyrauchen texanus) larvae from exposure to selenium and other trace elements in water and zooplankton collected from sites adjacent to the Colorado River near Grand Junction, CO. A 30-day study was initiated with 5-day-old larvae exposed in a 4�4 factor experiment with four food and four water treatments, and the biological endpoints measured were survival,...
We released semi-buoyant beads and marked razorback sucker larvae into the Green River during spring run-off in 2004, 2005, and 2006 to evaluate drift characteristics of larvae and beads into flood plain wetlands. Based on drift rates and capture patterns, our findings from 2004 main channel only sampling suggested that beads and tetracycline-marked fish larvae were reasonable surrogates for one another based on similarities in drift capture patterns. We also captured substantial numbers of unmarked, wild-produced razorback sucker larvae in 2004. This demonstrated that stocked adult fish were successfully reproducing and that another spawning area may exist downstream from Razorback Bar (now named ?Escalante Bar?),...
A hazard assessment was conducted based on information derived from two reproduction studies conducted with endangered razorback suckers (Xyrauchen texanus) at three sites near Grand Junction, CO, USA. Selenium contamination of the upper and lower Colorado River basin has been documented in water, sediment, and biota in studies by US Department of the Interior agencies and academia. Concern has been raised that this selenium contamination may be adversely affecting endangered fish in the upper Colorado River basin. The reproduction studies with razorback suckers revealed that adults readily accumulated selenium in various tissues including eggs, and that 4.6 Î&frac14;g/g of selenium in food organisms caused increased...
Effects on hatching and development of fertilized eggs in adult razorback sucker (Xyrauchen texanus) exposed to selenium in flooded bottomland sites near Grand Junction, Colorado, were determined. After 9 months exposure, fish were collected and induced to spawn and eggs collected for inorganic element analyses. A 9-day egg study was conducted with five spawns from Horsethief ponds, six spawns from Adobe Creek channel, and four spawns from North Pond using a reference water and site waters. Selenium concentrations in eggs were 6.5 microg/g from Horsethief, 46 microg/g from Adobe Creek, 38 microg/g from North Pond, and 6.0 microg/g from brood stock. Eggs from young adults had a smaller diameter and higher moisture...
A study was conducted with endangered the razorback sucker (Xyrauchen texanus) to determine if environmental exposure to selenium in flooded bottomland sites affected survival, growth, and egg-hatching success. Adults were stocked at three sites adjacent to the Colorado River near Grand Junction, Colorado, in July 1996: hatchery ponds at Horsethief Canyon State Wildlife Area (referred to here as Horsethief; the reference site), a diked tertiary channel at Adobe Creek, and North Pond at Walter Walker State Wildlife Area (WWSWA). Fish were collected in April 1997 and spawned. After two spawnings adults from the three sites were held at Horsethief for an 86-day selenium depuration period. Selenium concentrations at...