Chub Gila Research Articles

Relationship between Length of Roundtail Chub and Infection Intensity of Asian Fish TapewormBothriocephalus acheilognathi

Nonnative parasites have been blamed for the decline of native fish species in the American Southwest. The Asian fish tapeworm Bothriocephalus acheilognathi has parasitized many native fish species, but little is known of its effects on native cyprinid fish hosts. I found a strong negative correlation (Spearman's rank correlation, rs = −0.846; P < 0.001) between total length of roundtail chub Gila robusta and number of Asian fish tapeworms. A significant, but weaker negative correlation existed between weight of fish and number of tapeworms (rs = −0.687; P < 0.001). In addition, infected fish were significantly shorter (P = 0.0241) than uninfected fish. Infection by Asian fish tapeworm may slow growth, increase susceptibility to infestation, and increase predation on roundtail chub and possibly other native cyprinids.

Effects of Invasive Tissue Collection on Rainbow Trout, Razorback Sucker, and Bonytail Chub

Abstract Histological examination and biochemical assays of fish tissues are used for disease detection, genetic characterizations, contaminant analyses, and the detection of stable isotopes. However, tissue sampling usually requires invasive sampling procedures that may harm or kill an organism under investigation. For this reason, invasive procedures are rarely used with threatened, endangered, or other sensitive species. If invasive tissue sampling could be performed with little harm, a wide array of sophisticated techniques could be employed to assist in protection and management of species in decline. We subjected rainbow trout Oncorhynchus mykiss to nonlethal invasive sampling of fin, muscle, and liver tissue. Techniques first developed for trout were applied to two endangered fishes, razorback sucker Xyrauchen texanus and bonytail chub Gila elegans. Acute (mortality) and chronic (suppression of growth rate) effects of tissue removal were evaluated in a hatchery for control and treatment groups of e...

Avoidance Responses of Rainbow Trout andUtah Chub to Rotenone

Abstract Avoidance response to the piscicide rotenone was evaluated in rainbow trout Oncorhynchus mykiss and Utah chub Gila atraria. Each fish species was exposed to 12 separate test formulations that varied in the amount of rotenone present as well as the form of rotenone. Test formulations that contained no rotenone were water, liquid carrier, and inert powder. Formulations that contained rotenone (liquid rotenone, powdered rotenone, and a rotenone-only mixture) were tested at three different concentrations (0.045, 0.075, and 0.15 mg rotenone/L). Only rainbow trout exhibited an avoidance response in this study to the liquid and powdered formulations of rotenone. Presence of the carrier, piperonyl butoxide, in the liquid formulation may be a factor in rainbow trout avoidance of liquid rotenone, since trout avoided the liquid carrier treatment too.

Dispersal of Larval Fishes in a Regulated River Tributary

Abstract We investigated longitudinal distributions, nearshore movements, and drift of larval native fishes (humpback chub Gila cypha, speckled dace Rhinichthys osculus, bluehead sucker Catostomus discobolus, and flannelmouth sucker Catostomus latipinnis) in the Little Colorado River, a tributary to the regulated Colorado River in Grand Canyon, Arizona, to determine spawning sites, larval dispersal patterns, and amount of drift into the mainstem Colorado River. Larval distributions and drift indicated native fishes spawned throughout the terminal 14.2 km of the Little Colorado River. In addition, distribution, drift, and trap data suggest an active component to dispersal for all four native species. Drift of larval native fish was greater near shore than midchannel, and except for speckled dace larvae, which were prone to drift at night, larval native fish did not exhibit diel periodicity in drift. During a 46-d period in 1993, we estimated that over 370,000 native fish larvae drifted out of the Little Co...

Parasites and Fish Health in a Desert Stream, and Management Implications for Two Endangered Fishes

Abstract Reintroductions of the endangered razorback sucker Xyrauchen texanus and Colorado squawfish Ptychocheilus lucius into the Verde River, Arizona, have failed to establish self-sustaining populations. The failure of these reintroductions is often attributed to predation and competition by nonnative fishes and habitat loss, but parasite infestations (particularly a copepod, Lernaea cyprinacea) also have been implicated. We assessed the relationships among fish health, eukaryotic parasites, and bacterial and viral infections of these endangered fishes collected from two locations (Perkinsville and Childs) on the Verde River, Arizona, during February and June 1996. We also examined surrogate nonendangered native fishes (Sonora sucker Catostomus insignis, desert sucker Catostomus clarki, and roundtail chub Gila robusta) and nonnative species (common carp Cyprinus carpio and smallmouth bass Micropterus dolomieu) to determine if there were any systemwide patterns in parasite infestation and health of fish...

Resource Use by Larval and Early Juvenile Native Fishes in the Little Colorado River, Grand Canyon, Arizona

We investigated resource use by early life stage (≤30 mm, total length) humpback chub Gila cypha, speckled dace Rhinichthys osculus, bluehead suckers Catostomus discobolus, and flannelmouth suckers C. latipinnis in the Little Colorado River, a tributary to the Colorado River in Grand Canyon, Arizona. Significant logistic regression models for habitat use were developed for all species pairwise combinations except flannelmouth sucker–humpback chub and flannelmouth sucker–speckled dace; correct classification probabilities ranged from 54% to 81%. Parameters used in discriminating among habitat use included depth, distance from shore, cover, and substrate. Logistic models were also developed to compare habitat use among larval stages within species, and most combinations produced significant models. Classification probabilities ranged from 60% to 95% in these models with the variables of depth, distance from shore, current velocity, cover, and substrate contributing to the various models. Behavioral observations revealed significant differences in vertical use of the water column and feeding locations among bluehead suckers and the two cyprinids. Diet analysis supported differences observed in feeding location and also identified some differences in diel feeding patterns. These differences in habitat use, behavioral time budgets, and diet indicate that some resource partitioning occurs among larval fishes in the Little Colorado River. Further laboratory study is needed to verify the mechanisms that sustain differential resource use in this system.

Effects of Electrofishing Fields on Captive Juveniles of Two Endangered Cyprinids

Abstract We conducted laboratory experiments to address concerns about potential harmful effects of electrofishing on juvenile humpback chubs Gila cypha. Four types of square-wave pulsed DC in homogeneous fields were tested: 30 Hz (12% duty cycle), 60 Hz (24% duty cycle), 80 Hz (40% duty cycle), and a complex pulse train of three 240-Hz, 2.6-ms pulses delivered at 15 Hz (12% duty cycle). We first determined peak-voltage gradients for each current sufficient to induce the electroshock responses of taxis, narcosis, or tetany in captive-reared early juvenile humpback chubs (49–96 mm total length) and bonytails G. elegans (46–79 mm). Bonytails were intended as surrogates for humpback chubs in most subsequent tests. However, mean voltage-gradient response thresholds were 8–43% lower for humpback chubs than for bonytails. We then exposed 30 humpback chubs for 10 s to the complex pulse current at mean tetanizing field intensity and 60 bonytails for 10 s to one of the four currents at mean field intensities requi...

Predation by Introduced Fishes on Endangered Humpback Chub and other Native Species in the Little Colorado River, Arizona

Abstract Fishes in the Little Colorado River in the Grand Canyon, Arizona, were sampled monthly from July 1991 to June 1995 as part of a study of the ecology of endangered humpback chub Gila cypha. Diets of five introduced predatory fish species were examined. Stomach contents varied among species and were low in diversity and dominated by algae (primarily Cladophora), aquatic insects, and fishes. Humpback chub plus other native species were a significant component of the diet (13.7% frequency of occurrence among 219 of 408 stomachs that contained food). Predation mortality from introduced fishes may significantly affect the native species by depleting numbers and reducing recruitment.

Competition between Kokanees and Utah Chub in Flaming Gorge Reservoir, Utah–Wyoming

Kokanees Oncorhynchus nerka (lacustrine sockeye salmon) and Utah chub Gila atraria feed extensively on similar sizes and species of zooplankton in Flaming Gorge Reservoir. We measured the effects of Utah chub on the growth of kokanees in six 80-m3 enclosures containing ambient zooplankton populations. Three kokanees and 0, 3, 6, 12, or 24 Utah chub were weighed and placed in each enclosure. After 21 d, fish were removed and kokanee growth was compared among treatments. Zooplankton biomass, chlorophyll-a concentrations, and temperature profiles were monitored during each test. In May 1992, no competitive interactions were observed; in June 1992, however, zooplankton biomass and kokanee growth declined significantly as Utah chub densities increased. The best predictor of kokanee growth was Daphnia pulex density, which explained 76% of the variance in kokanee growth. Differences in temperature and initial zooplankton biomass affected the strength of observed competition. Our results suggest that monitoring forage resources rather than nongame fish densities may provide a better framework for assessing competition among pelagic fish species.

Cormorant and Grebe Predation on Rainbow Trout Stocked in a Southern Utah Reservoir

Abstract We investigated poststocking losses of rainbow trout Oncorhynchus mykiss to avian predation in Minersville Reservoir, Utah. Double-crested cormorants Phalacrocorax auritus and western grebes Aechmophorus occidentalis consumed 31.3% and 8.8% of the planted fingerlings in 2-week periods following stocking in April and June 1988, respectively. Piscivorous birds were associated both spatially and chronologically with fingerling trout in the reservoir. The birds consumed hatchery trout far more frequently than they did Utah chub Gila atraria, which were abundant in the reservoir. Subadult rainbow trout and cutthroat trout O. clarki composed 75.0% of the diet, by biomass, of double-crested cormorants sampled. Double-crested cormorants removed more trout from Minersville Reservoir than did anglers.

Prehistoric Native American Fisheries of the Central California Coast

Over 77,000 fish remains from 51 archaeological sites on the central California coast between San Mateo and San Luis Obispo counties, deposited between 6200 B.c. and A.D. 1830, were studied to assess prehistoric species distribution, diversity, and Native American fisheries. Remains were obtained from exposed rocky coastal sites, lagoon–estuaries at Elkhorn Slough and Morro Bay, and the freshwater drainages of the Pajaro and Salinas rivers. On the rocky coast, 58.4% of the remains represented large inshore species, 26.9% were small schooling species, and 11.8% were surfperches (family Embiotocidae). Large inshore species included rockfishes Sebastes spp., lingcod Ophiodon elongates, kelp greenling Hexagrammos decagrammus, cabezon Scorpaenichthys marmoratus, and monkeyface prickleback Cebidichthys violaceus. At Elkhorn Slough and Morro Bay, about half of the remains of marine species represented moderately small schooling species, including Pacific herring Clupea pallasi, Pacific sardine Sardinops sagax, northern anchovy Engraulis mordax, topsmelt Atherinops affnis, jacksmelt Atherinopsis californiensis, and California grunion Leuresthes tenuis. Surfperches also were common, and specialized local fisheries for flounders or sharks and rays were suggested. Aquatic conditions at Elkhorn Slough were dramatically different from those that exist today. Sites on Elkhorn Slough had both marine and freshwater fishes and showed site occupation when the Salinas River entered the slough and did not follow its present course into Monterey Bay. Sacramento perch Archoplites interruptus was the most abundant species found at freshwater sites, and remains of extinct thicktail chub Gila crassicauda confirm its presence in the Pajaro and Salinas rivers. Surprisingly rare are the remains of steelhead (the anadromous form of rainbow trout) Oncorhynchus mykiss. As is the case today, Pacific salmon were apparently absent from central coast streams south of the San Lorenzo River. Presumably the remains reflect local species availability.

Notes: Nitrogen Excretion in Four Species of Fish from an Alkaline Lake

Abstract In this study, we examined the ammonia and urea excretion rates in four species of fish native to Pyramid Lake, Nevada (pH 9.4): tui chub Gila bicolor, Tahoe sucker Catostomus tahoensis, Lahontan cutthroat trout Oncorhynchus clarki henshawi, and cui-ui Chasmistes cujus. The activities of liver enzymes associated with the ornithine urea cycle and uricolysis were also measured in all but cui-ui. As in other teleost fish, most of the nitrogen was excreted as ammonia. Ammonia excretion rates ranged from 48 to 342 μmol N·kg−1·h−1. Urea excretion rates varied from 17 to 139 μmol N·kg−1·h−1. The proportion of nitrogenous waste excreted by fish as urea in the alkaline Pyramid Lake water was greater than by fish in neutral water; however, ornithine urea cycle enzyme activities, with the exception of arginase (range, 5.2–41.0 μmol·g−1·min−1), were relatively low. All three of the uricolytic enzymes were present in significant activities. Therefore, it seems that urea is produced in these fish by uricolysis...

A Nonlethal Technique to Recover Gut Contents of Roundtail Chub

Abstract Forty adult roundtail chub Gila robusta, captured by electrofishing from the Colorado River in Colorado, were used to evaluate a nonlethal stomach-pumping technique for recovering gut contents. Twenty roundtail chub were subjected to stomach pumping; another 20 were used as controls and not pumped. Gut contents were flushed from the anal vent instead of the buccal cavity, because the simple S-shaped gut and lack of a pyloric sphincter in roundtail chubs allowed the free passage of intestinal material. A necropsy revealed that the technique evacuated 100% of gut contents, with no apparent damage to the pharyngeal teeth, esophagus, or intestinal lining. Long-term effects were not evaluated, but no short-term ill effects were observed. This technique is recommended as a safe, efficient, and nonlethal procedure for recovering gut contents of roundtail chub. The technique may also be applicable to the endangered humpback chub G. cypha and bonytail chub G. elegans, closely-related species with nearly i...

Effects of Pulsed DC Electroshock on Adult Roundtail Chub from the Colorado River in Colorado

Abstract Forty adult roundtail chub Gila robusta were captured by pulsed DC electroshock from the Colorado River near the Colorado–Utah state line and examined for spinal injury and tissue damage by X rays and necropsy. The fish were captured from an electrofishing boat, by means of a Coffelt V VP- 15 electrofisher with a square waveform pulsed DC output of 120 V and 8 A (20% duty cycle, 40 Hz). No external bruises or abnormal behavior were noted immediately after electroshocking. Open-fillet necropsy revealed local hemorrhaging along a portion of the spine in 5% (two) of the fish, and no dislocated or fractured vertebrae were observed in the X-ray photographs. Electrofishing with square-wave pulsed DC at 40 Hz was determined to be a safe method for capturing native roundtail chub from the Colorado River, when used under these conditions.

Summer Habitat Use by Littoral-Zone Fishes in Lake Tahoe and the Effects of Shoreline Structures

We used scuba observations to determine summer habitat use and the effects of piers on the littoral-zone fish community in Lake Tahoe, California–Nevada. Habitat complexity declined with depth. Over 50% of the littoral zone less than 2 m deep was composed of complex boulder substrates, but this substrate represented less than 10% of the habitat between 10 and 18 m deep. A severe drought lowered the surface elevation of the lake 2 m and reduced the wetted complex rocky habitat by 20% between the 0- and l0-m isobaths (referenced to the mean lake level of 1,899 m above sea level). The dominant littoral-zone fish, adult Lahontan redsides Richardsonius egregius, were found at depths ranging from 1–10 m over substrates, but at somewhat greater depths (3–10 m) over cobble–boulder substrates. Juvenile Lahontan redsides were concentrated around boulders at depths of 1–3 m, and their densities were much lower than the densities of adults. Adult tui chub Gila bicolor and rainbow trout Oncorhynchus mykiss were also most often associated with complex boulder habitats. The daytime densities and species composition of fishes associated with piling-supported piers did not differ significantly from adjacent no-pier areas, whereas the densities of Lahontan redsides, tui chubs, Lahontan speckled dace Rhynichthys osculus robustus, and Tahoe suckers Catostomus tahoensis associated with the complex structure of rock-crib piers were significantly higher than in adjacent no-crib areas. Fish density increased 5–12-fold at night relative to the observed daytime densities in the pier, rock-crib, no-pier, and no-crib transects.

Lake Trout Consumption and Recent Changes in the Fish Assemblage of Flaming Gorge Reservoir

Abstract Bioenergetics modeling was used to quantify the consumption dynamics of lake trout Salvelinus namaycush in Flaming Gorge Reservoir, Utah–Wyoming. Analysis of diet and population estimates of different size-classes of lake trout indicated that kokanees Oncorhynchus nerka made up the greatest proportion of prey biomass. Examination of growth rates of forage fish and predator–prey size ratios indicated that Utah chub Gila atraria were more vulnerable than kokanees to lake trout predation. Utah chub grow slower than kokanees and thus were susceptible to piscivores over a longer age span. We conclude that kokanees will make up an even larger proportion of the pelagic fish assemblage of Flaming Gorge Reservoir in future years.

Macrohabitat of Sonora Chub (Gila ditaenia) in Sycamore Creek, Santa Cruz County, Arizona

ABSTRACT Physical characteristics and persistence of macrohabitat used by different life stages of Sonora chub (Gila ditaenia) were determined by repeatedly measuring distinct reaches in Sycamore Creek, Santa Cruz County, Arizona, in 1990 and 1991. At the beginning of summer drought, habitats occupied by adult Sonora chub were deeper and larger than areas with only immature fish and unoccupied areas. The medians of maximum depth were 47.0 cm (1990) and 39.7 cm (1991) for habitats with adults, 21.3 cm (1990) and 22.9 cm (1991) for habitats with only immature fish, and 14.6 cm (1990) and 19.7 cm (1991) for unoccupied areas. At the end of summer drought, adults occupied habitats that were deeper and larger, and the percent decrease in area and depth was less than areas containing only immature fish or no fish. The medians of percent decrease in maximum depth were 13% (1990) and 21% (1991) for habitats with adults, 48% (1990) and 41% (1991) for habitats with only immature fish, and 42% (1990) and 33% (1991) f...

Genetics and morphology of Yaqui chub Gila purpurea, an endangered cyprinid fish subject to recovery efforts

Federally endangered Yaqui chubs Gila purpurea are restricted to the Rio San Bernardino, a small headwater tributary of the vast Rio Yaqui basin of Sonora, México, and Arizona, United States. The species faced almost certain extirpation in the United States during the late 1960s when its remaining habitats went dry. Just prior to that event in 1969, individuals were successfully transplanted into nearby Leslie Creek. Captive propagation was later used to produce fish to re-establish populations in its native range after habitats were reclaimed and protected. We present the history of conservation efforts which include numerous transfers of differing numbers of fish between captive and ‘wild’ stocks. We examined the effects of these recovery efforts on the genetic and phenotypic structure of populations. Genetic and morphological differentiation were respectively assessed using allozyme electrophoresis and principal components analysis. Considerable genetic stability was indicated, with observed variations attributable to documented or inferred changes in population sizes. Morphology also remained uniform, both temporally and spatially, with no evidence of changes attributable to recovery manipulations or ecophenotypic responses to novel environments. Yaqui chubs exhibit high fecundity and quickly establish large effective population sizes, life history characteristics which likely account for the minimal effects of population manipulations.

Discriminant Separation of Fishes: A Preliminary Study of Fish Eggs by Curie-Point Pyrolysis–Mass Spectrometry–Chemometric Analysis

Abstract We conducted preliminary research to assess a new, nonlethal method for identifying larval fishes below currently recognized species levels. We used Curie-point pyrolysis and mass spectrometry to discriminate among fish egg samples representing Colorado squawfish Ptychocheilus lucius, Pahranagat roundtail chub Gila robusta jordani, and, two populations of cutthroat trout Oncorhynchus clarki. When preliminary data were processed by unsupervised pattern recognition (multivariate cluster and display methods), the species could be clearly discriminated. Variation within cutthroat trout samples was greater than variation in the other species. Results show that Curie-point pyrolysis with mass spectrometry provides characteristic chemotaxonomic information for the samples.

Temporal and Spatial Relations between the Spawning of Humpback Chub and Roundtail Chub in the Upper Colorado River

Gonadosomatic indices (100 × gonad weight/whole-body weight) and the occurrence of expressible gametes indicated a temporal overlap in the spawning of humpback chub Gila cypha and roundtail chub G. robusta at Black Rocks, a turbulent, deepwater reach of the upper Colorado River, Colorado (39°N, 109°W). Radiotelemetry showed that roundtail chub moved throughout the upper Colorado River during the spawning season, whereas humpback chub were restricted almost entirely to the 1.8-km Black Rocks reach; however, spatial isolation of the species during spawning was not demonstrated. A principal component analysis of morphologic measurements taken from live fish supported taxonomic assignments made in the field and suggested that most of the few specimens considered hybrids or intergrades by field personnel were actually humpback chub; however, an analysis based on fin ray counts indicated that this group included roundtail chub, hybrids, or backcross individuals. The strong affinity of humpback chub for the unique habitat conditions created by water flowing rapidly among large, angular boulders and shoreline rock outcrops at Black Rocks and elsewhere suggests that the unusual morphology of this species is an adaptation to life in such habitats. The limited availability of such habitats might be an important factor controlling the distribution and relative abundance of the humpback chub, a species now listed as endangered.