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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...
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Population sizes, movements, and potential hybridization were examined for two indigenous Colorado River fishes, Catostomus latipinnis (flannelmouth sucker) and Xyrauchen texanus (razorback sucker) in the Little Colorado River (LCR) of Grand Canyon National Park and the Navajo Nation (Coconino County, AZ). Catostomus latipinnisis a "species of concern," and X. texanusis federally listed as endangered. Within Grand Canyon, both occur in greatest abundance in the LCR and its confluence with the mainstem Colorado River. During a 50-trip period (1 July 1991-27 June 1995), 2619 unique individuals (> 150 mm TL) were evaluated, consisting of 2578 C. latipinnis and 41 putative X. texanus/C. latipinnis hybrids. Cormack-Jolly-...
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The extant genetic variation of a population is the legacy of both long-term and recent population dynamics. Most practical methods for estimating effective population size are only able to detect recent effects on genetic variation and do not account for long-term fluctuations in species abundance. The utility of a maximum likelihood estimator of long-term effective population size based upon the coalescent theory of gene genealogies is examined for three endangered Colorado River fishes: humpback chub (Gila cypha), bonytail chub (Gila elegans) and razorback sucker (Xyrauchen texanus). Extant mitochondrial DNA (mtDNA) variation in humpback chub suggests this species has retained its historical equilibrium genetic...
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Razorback sucker (Xyrauchen texanus [Abbott]), bonytail (Gila elegans Baird and Girard) and humpback (G. cypha Miller) chubs, and Colorado squawfish (Ptychocheilus lucius) Girard) comprise the endemic "big river" fish fauna of the Colorado River, western North America. All are near extirpation in the wild. Effects of incubation temperature upon embryo hatch success were experimentally examined to evaluate potential impacts of cold hypolimnetic reservoir releases upon species reproductive success. Eggs were spawned and fertilized at 18?C, and embryos incubated at 5, 10, 15, 20, 25, and 30?C. Total mortality of embryos of all species occurred in 12-96 hours at 5, 10, and 30?C; and in 48-60 hours at 15?C for P. lucius...
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he razorback sucker Xyrauchen texanus is an endangered fish endemic to the Colorado River basin in the western United States. Once widely distributed and common throughout the basin, the species has been eliminated from most of its former range by establishment of nonnative fishes and water development, and remaining numbers have dwindled precipitously from historical levels. Although Lake Mohave, Arizona and Nevada, supports the largest and genetically most diverse remaining population, razorback sucker abundance in the lake plummeted from historical numbers in the hundreds of thousands to only 44,000 in 1991 and fewer than 3,000 in 2001. This population is limited primarily to large, old adults because predation...
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