Humpback Chub Research Articles

Modelling effects of discharge on habitat quality and dispersal of juvenile humpback chub (Gila cypha) in the Colorado River, Grand Canyon

AbstractA two‐dimensional hydrodynamic model was applied to seven study reaches in the Colorado River within Grand Canyon to examine how operation of Glen Canyon Dam has affected availability of suitable shoreline habitat and dispersal of juvenile humpback chub (Gila cypha). Suitable shoreline habitat typically declined with increasing discharges above 226–425 m3/ s, although the response varied among modelled reaches and was strongly dependent on local morphology. The area of suitable shoreline habitat over cover types that are preferred by juvenile humpback chub, however, stayed constant, and in some reaches, actually increased with discharge. In general, changes in discharge caused by impoundment tended to decrease availability of suitable shoreline habitat from September to February, but increased habitat availability in spring (May–June). Hourly variation in discharge from Glen Canyon Dam substantially reduced the amount of persistent shoreline habitat at all reaches. Changes in suitable shoreline habitat with discharge were shown to potentially bias historical catch per unit effort indices of native fish abundance up to fourfold. Physical retention of randomly placed particles simulating the movement of juvenile humpback chub in the study reaches tended to decline with increasing discharge, but the pattern varied considerably due to differences in the local morphology among reaches and the type of swimming behaviour modelled. Implications of these results to current hypotheses about the effects of Glen Canyon Dam on juvenile humpback chub survival in the mainstem Colorado River are discussed. Copyright © 2004 John Wiley & Sons, Ltd.

PARASITES OF NATIVE AND NONNATIVE FISHES OF THE LITTLE COLORADO RIVER, GRAND CANYON, ARIZONA

A 2-yr, seasonal, parasitological study of 1,435 fish, belonging to 4 species of native fishes and 7 species of nonnative fishes from the lower Little Colorado River (LCR) and tributary creeks, Grand Canyon, Arizona, yielded 17 species of parasites. These comprised 1 myxozoan (Henneguya exilis), 2 copepods (Ergasilus arthrosis and Lernaea cyprinacea), 1 acarine (Oribatida gen. sp.), 1 piscicolid leech (Myzobdella lugubris), 4 monogeneans (Gyrodactylus hoffmani, Gyrodactylus sp., Dactylogyrus extensus, and Ligictaluridus floridanus), 4 nematodes (Contracaecum sp., Eustrongylides sp., Rhabdochona sp., and Truttaedacnitis truttae), 3 cestodes (Bothriocephalus acheilognathi, Corallobothrium fimbriatum, and Megathylacoides giganteum), and 2 trematodes (Ornithodiplostomum sp. and Posthodiplostomum sp.). Rhabdochona sp. was the only adult parasite native to the LCR. Infection intensities of Ornithodiplostomum sp. and B. acheilognathi were positively correlated with length of the humpback chub Gila cypha. Adult helminths showed a high degree of host specificity, except B. acheilognathi, which was recovered from all fish species examined but was most abundant in cyprinids. Abundance of B. acheilognathi in the humpback chub was highest in the fall and lowest in the summer in both reaches of the LCR. There was no major taxonomic difference in parasite assemblages between the 2 different reaches of the river (LC1 and LC2). Parasite community diversity was very similar in humpback chub, regardless of sampling site or time. The parasite fauna of the LCR is numerically dominated by B. acheilognathi and metacercariae of Ornithodiplostomum sp. The richest and most diverse component community occurred in a nonnative species, the channel catfish Ictalurus punctatus, but infracommunity species richness was highest in a native host, humpback chub.

Development of microsatellite markers in bonytail (Gila elegans) with cross‐species amplification in humpback chub (Gila cypha)

AbstractBonytail, Gila elegans, is an endangered species of fish native to the Colorado River. Primers are presented for 17 microsatellites cloned from bonytail as well as the results of test amplifications in bonytail and humpback chub, G. cypha. Bonytail exhibited three to 18 alleles per locus across the 17 microsatellites and a mean expected heterozygosity of 0.58 among 10 loci used to screen 160 broodstock. Humpback chub exhibited one to six alleles and a mean expected heterozygosity of 0.69 among 10 loci that were successfully amplified in that species.

Long‐term effective population size of three endangered Colorado River fishes

AbstractThe 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 variation despite recent declines in abundance. The mtDNA variation in razorback suckers indicates the population was quite large and expanding prior to recent declines and that rare alleles still survive in the remnant populations. The remaining mtDNA variation in bonytail chub indicates that dramatic, recent declines may have already obliterated a substantial portion of any historical variation. The results from long‐term effective population size analyses are consistent with known natural history and illustrate the utility of the analysis for endangered species management.

Food Web Implications of δ13C and δ15N Variability over 370 km of the Regulated Colorado River USA

Dual stable isotope analysis in the regulated Colorado River through Grand Canyon National Park, USA, revealed a food web that varied spatially through this arid biome. Down-river enrichment of δ13C data was detected across three trophic levels resulting in shifted food webs. Humpack chub δ13C and δ15N values from muscle plugs and fin clips did not differ significantly. Humpback chub and rainbow trout trophic position is positively correlated with standard length indicating an increase in piscivory by larger fishes. Recovery of the aquatic community from impoundment by Glen Canyon Dam and collecting refinements for stable isotope analysis within large rivers are discussed.

Juvenile Growth of Native Fishes in the Little Colorado River and in a Thermally Modified Portion of the Colorado River

We estimated juvenile growth rates of four native fish species using the von Bertalanffy growth equation and length data from fish captured during 1991–1994 in the Little Colorado River, a tributary to the Colorado River in Arizona in the Grand Canyon. We compared growth rates to water temperatures for all four species and modeled the effects of warming the Colorado River (through a proposed retrofit of Glen Canyon Dam) on the growth of age-0 emigrants from the tributary. Juvenile growth rates in the Little Colorado River were fastest for flannelmouth sucker Catostomus latipinnis, slowest for speckled dace Rhinichthys osculus, and intermediate for humpback chub Gila cypha and bluehead sucker Catostomus discobolus. Growth rates for each species were positively correlated with water temperature; flannelmouth sucker exhibited the strongest relationship, followed by speckled dace, humpback chub, and bluehead sucker. Our model indicates that native fish immigrating into the cold Colorado River (8–12°C) from the relatively warm Little Colorado River during their first 3 months of life will grow very little by the end of their first year. According to other studies, older, larger fish that disperse into the Colorado River are more likely to survive than those that migrate as larvae. Growth, and possibly survival, of native fish larvae that drift from tributaries into the Colorado River could be increased if water released from Glen Canyon Dam is warmed during the period of larval drift.

EFFECTS OF A TEST FLOOD ON FISHES OF THE COLORADO RIVER IN GRAND CANYON, ARIZONA

A beach/habitat-building flow (i.e., test flood) of 1274 m3/s, released from Glen Canyon Dam down the Colorado River through Grand Canyon, had little effect on distribution, abundance, or movement of native fishes, and only short-term effects on densities of some nonnative species. Shoreline and backwater catch rates of native fishes, including juvenile humpback chub (Gila cypha), flannelmouth suckers (Catostomus latipinnis), and bluehead suckers (C. discobolus), and all ages of speckled dace (Rhinichthys osculus), were not significantly different before and after the flood. Annual spring spawning migrations of flannelmouth suckers into the Paria River and endangered humpback chub into the Little Colorado River (LCR) took place during and after the flood, indicating no impediment to fish migrations. Pre-spawning adults staged in large slack water pools formed at the mouths of these tributaries during the flood. Net movement and habitat used by nine radio-tagged adult humpback chub during the flood were no...

Effects of a Test Flood on Fishes of the Colorado River in Grand Canyon, Arizona

A beach/habitat-building flow (i.e., test flood) of 1274 m3/s, released from Glen Canyon Dam down the Colorado River through Grand Canyon, had little effect on distribution, abundance, or movement of native fishes, and only short-term effects on densities of some nonnative species. Shoreline and backwater catch rates of native fishes, including juvenile humpback chub (Gila cypha), flannelmouth suckers (Catostomus latipinnis), and bluehead suckers (C. discobolus), and all ages of speckled dace (Rhinichthys osculus), were not significantly different before and after the flood. Annual spring spawning migrations of flannelmouth suckers into the Paria River and endangered humpback chub into the Little Colorado River (LCR) took place during and after the flood, indicating no impediment to fish migrations. Pre-spawning adults staged in large slack water pools formed at the mouths of these tributaries during the flood. Net movement and habitat used by nine radio-tagged adult humpback chub during the flood were not significantly different from prior observations. Diet composition of adult humpback chub varied, but total biomass did not differ significantly before, during, and after the flood, indicating opportunistic feeding for a larger array of available food items displaced by the flood. Numbers of nonnative rainbow trout (Oncorhynchus mykiss) <152 mm total length decreased by ∼8% in electrofishing samples from the dam tailwaters (0–25 km downstream of the dam) during the flood. Increased catch rates in the vicinity of the LCR (125 km downstream of the dam) and Hell's Hollow (314 km downstream of the dam) suggest that these young trout were displaced downstream by the flood, although displacement distance was unknown since some fish could have originated from local populations associated with intervening tributaries. Abundance, catch rate, body condition, and diet of adult rainbow trout in the dam tailwaters were not significantly affected by the flood, and the flood did not detrimentally affect spawning success; catch of young-of-year increased by 20% in summer following the flood. Post-flood catch rates of nonnative fathead minnows (Pimephales promelas) in shorelines and backwaters, and plains killifish (Fundulus zebrinus) in backwaters decreased in the vicinity of the LCR, and fathead minnows increased near Hell's Hollow, suggesting that the flood displaced this nonnative species. Densities of rainbow trout and fathead minnows recovered to pre-flood levels eight months after the flood by reinvasion from tributaries and reproduction in backwaters. We concluded that the flood was of insufficient magnitude to substantially reduce populations of nonnative fishes, but that similar managed floods can disadvantage alien predators and competitors and enhance survival of native fishes.

Use of Geometric Morphometrics to DifferentiateGila(Cyprinidae) within the Upper Colorado River Basin

Abstract Video images of 215 adult Gila robusta and 148 endangered Gila cypha were collected from May 1991–October 1992 at eight Colorado River basin localities (seven upper basins and one lower basin). The two species were sympatric at five of these locations; G. robusta was absent at one site, whereas G. cypha was missing at two others. Saggital views of each individual were videotaped and 25 morphological points (15 anatomical landmarks and 10 helping points) identified. Bookstein shape coordinates were calculated from Cartesian coordinates of these landmarks and points, whereas centroid size was used as a measure of body size. Shape differences were evaluated among populations of each species using MANOVA and canonical variates analysis. In G. cypha, variation encompassed three aspects: nuchal hump (most pronounced in Grand Canyon forms), relative head size (larger in Cataract Canyon forms), and caudal peduncle dimensions (shorter with a tapering depth in Cataract Canyon forms but longer and uniformly...

Nonnative Fish Control and Endangered Fish Recovery: Lessons from the Colorado River

Native freshwater fish populations are declining in North America and more than 100 fishes are federally listed as threatened or endangered. The Colorado River system in the southwestern United States has been especially affected. Most of its native fish populations are in decline, including four “big river” fishes, Colorado pikeminnow (Ptychocheilus lucius), humpback chub (Gila cypha), bonytail (G. elegans), and razorback sucker (Xyrauchen texanus), whose populations have declined so precipitously that they are endangered. Physical habitat alteration caused native fish declines, but nonnative fishes pose a more serious threat to native fishes than previously thought. Nonnative fish control measures needed in the upper Colorado River system, identified in part by a workshop of experts, include: (1) preventing movements of game fishes out of impoundments and curtailing future stockings, (2) reducing numbers of small, nonnative cyprinids in shoreline habitat used as rearing areas by young native fishes, and (3) increasing the harvest of channel catfish (Ictalurus punctatus) and common carp (Cyprinus carpio) in the mainstream. Large-scale implementation of these nonnative fish control measures has proven difficult. Recovery efforts have identified the need for developing nonnative fish control strategies and testing methodologies, but no solutions have emerged. A holistic approach, including ecosystem recovery plans, should be used in systems where more than one species share common problems, such as interactions with nonnative fishes. Nonnative fish interactions should be suspected as a potential cause of declining native fish populations.

Temperature Effects of Hypolimnial-Release Dams on Early Life Stages of Colorado River Basin Big-River Fishes

Declines of native big-river fishes of the Colorado River Basin, southwestern United States, have been attributed in part to emplacement of hypolimnial-release dams. Lowered spring-summer tailwater temperatures inhibit spawning and embryonic development, depress swimming performance and growth, and reduce survival of early life stages. We examined effects of three temperatures (10 C, 14 C, 20 C) on aspects of growth, development, and physiology of larval and early juvenile life stages of Xyrauchen texanus (Razorback Sucker), Catostomus latipinnis (Flannelmouth Sucker), Gila cypha (Humpback Chub), and Ptychocheilus lucius (Colorado Squawfish) in the laboratory. Lengths, weights, and specific growth rates of all species were significantly lower at 10 C and 14 C than at 20 C, and time to transformation from larval to juvenile life stage was delayed at colder temperatures. Transfer of fishes from 20 C to 10 C (simulating transport from warm tributaries to cold tailwaters) caused loss of equilibrium in youngest life stages. All these effects increase exposure of larvae to existing sources of mortality. Conservation of the big-river species in hypolimnial-release tailwaters will require thermal modification of dam discharges to lessen detrimental effects of cold water temperatures. Because such action may also benefit nonindigenous biota, recovery of the native fauna may ultimately depend upon implementation of comprehensive (and likely expensive) control measures against nonnative species.

Spatiotemporal Variation in Length–Weight Relationships of Endangered Humpback Chub: Implications for Conservation and Management

The largest population of endangered humpback chub Gila cypha inhabits the lower Little Colorado River (LCR) and the main-stem Colorado River near its confluence with the LCR in Grand Canyon, Arizona. At present, fish in both rivers spawn almost exclusively in the LCR. Flows in the main-stem Colorado River are regulated by Glen Canyon Dam, and water temperature approximates predam winter temperatures year-round. The LCR continues to provide a relatively natural hydrograph and seasonal warming patterns. Length–weight relationships among adult humpback chub from the lower Colorado River basin showed a seasonal pattern of declining condition during spring spawning season followed by recovery of condition during summer through early winter. Fish from the main stem recovered condition more rapidly after reproduction than did fish from the LCR and may have benefited from dam-mediated environmental changes. Grand Canyon Colorado River fish had the greatest weight at length of eight locations sampled in the upper and lower basins. Records since 1978 indicate a decline in condition of lower basin humpback chub coincident with a reported decline in population size in Grand Canyon. We recommend increased monitoring of all populations, including mark–recapture studies to provide population estimates during the spawning season and condition monitoring during October–November to determine more subtle changes in fish health.

Ecology of spawning humpback chub, Gila cypha, in the Little Colorado River near Grand Canyon, Arizona

The morphologically unique and endangered humpback chub, Gila cypha, is found in canyon-bound reaches of the Colorado River and its tributaries. Now limited to six isolated reproducing populations, this species is believed to have been once distributed over a large portion of the mainstem river. Because the species inhabits remote canyon areas, little is known about its spawning ecology. The largest remaining population occurs in the lower Little Colorado River (LCR) near Grand Canyon, where we conducted a three-year study of spawning ecology during spring (March-June) 1993–1995. We analyzed seasonal patterns of movement, population density, relative condition, spawning scores, and frequency of ripe condition and fin abrasions and compared these data with seasonal discharge and water temperature to determine spawning phenology and ecology. Spawning commenced in late March, peaked in mid-April, and waned in mid-May. A high proportion of males remained ripe over this period, whereas ripe females were relatively abundant only in April. Increased densities of adult fish in March-April and rapid declines in May-June coupled with recaptures of 18.4% of these adults in the Colorado River suggest that a portion of the population migrated from the Colorado River into the LCR to spawn and then returned. Ripe males aggregated in areas of complex habitat structure with high angular variation in bottom profiles (matrix of large boulders, travertine masses combined with chutes, runs and eddies, 0.5–2.0 m deep) and were associated with deposits of clean gravel. Ripe females appeared to move to these male aggregations to spawn. Near-spawning (including gravid) females and non-spawning fish used similar habitats and were segregated but close (< 50 m) to habitats occupied by aggregations of ripe males. Abrasions on anal and lower caudal fins of males and females suggest that spawning involves contact with gravel substrates, where semi-adhesive eggs are deposited and fertilized. The findings of this study should aid recovery efforts for humpback chub by identifying spawning habitat within the historic distributional range where additional spawning stocks could be established.

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...

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.

Habitat relationships of subadult humpback chub in the Colorado River through Grand Canyon: spatial variability and implications of flow regulation

We examined subadult humpback chub densities along 24 kms of the Colorado River in the Grand Canyon to: (1) identify geomorphic conditions in the study area; (2) determine associations between subadult humpback chub (<200 mm TL) habitat use and geomorphic differences; and (3) determine how discharge, during base flow conditions, was related to subadult humpback chub habitat conditions. Habitat was categorized at two nested spatial scales: geomorphic reach and shoreline type. Within reaches, shoreline types were categorized according to geomorphology. We measured water depth, velocity and cover attributes along all shoreline types over a range of discharges to determine if habitat quality of reaches and shoreline types varied with discharge. Reaches 1 and 3 had narrow, deep corridors, whereas Reach 2 was a wide, shallow reach. Among shoreline types, depth, velocity and cover varied; however, differences were not consistent between reaches. Fish densities also varied among shoreline types and reaches. Vegetation, talus and debris fan shorelines had the highest densities of subadult humpback chub in a pattern similar to that of cover. In addition, subadult humpback chub presence was associated with a high frequency of cover regardless of shoreline designation. However, these relationships explained little of the overall variation in subadult densities. Lack of a strong association between fish density and geomorphology may be partially due to effects of discharge on habitat quality. The overall trend among shorelines (without regard to type) showed that cover decreased with increasing discharge, whereas depth and velocity increased. However, no consistent pattern between discharge and depth, velocity and cover among individual shoreline types was evident. Vegetated shorelines, consisting mainly of non-native tamarisk (Tamarix chinensis), had nearly twice the fish densities of talus and debris fan. Reasons are discussed as to why subadult humpback chub occupy naturalized habitat like vegetated shorelines in greater densities than natural habitats. The relationships observed in this study have important implications for humpback chub recovery and management of the Colorado River through Grand Canyon. © 1998 John Wiley & Sons, Ltd.

Multivariate Discrimination of Colorado PlateauGilaspp.: The “Art of Seeing Well” Revisited

Fishery managers have long been troubled by phenotypic variation within and among Colorado Plateau Gila. The problem is twofold. From an historical perspective, there was reticence to investigate fishes long considered as “undesirable.” In a taxonomic sense, there is confusion over within- and among-species variability. We document the former, then clarify the latter by applying discriminant analysis to meristic and morphometric data collected from museum specimens. We test three hypotheses: roundtail chub G. robusta humpback chub G. cypha and bonytail G. elegans are morphologically indistinguishable; juveniles are assignable to species based upon adult characters; and putative hybrids are morphologically intermediate between parental forms. Through the use of meristic characters in a nonparametric discriminant analysis, over 95% of all adults were segregated to species. By using morphometric characters, 97% could be allocated to species. Gila robusta was easily separated from G. cypha and G. elegans. The latter were most difficult of all species-pairs to discriminate, yet field characters still segregated them at better than 95%. A discriminant function, based upon five morphometric characters, will allocate unknowns to species. Juvenile G. robusta were easily discriminated (>97%), but juveniles of G. cypha and G. elegans were often misidentified as G. robusta. Putative hybrids were generally assigned to one or the other parental form; thus, hybrid intermediacy could not be rejected. However, paucity of hybrids weakened the test. We conclude that factors most important in segregating these species are character selection, adequate analyses, and “the art of seeing well.”

Early Records of the Endangered Fish Gila cypha Miller from the Yampa River of Colorado with Notes on Its Decline

ceedingly sparse. There are several reasons for this lack of knowledge. The species was not described until 1946 (Miller, 1946), and prior to that time it was included as part of the endemic Colorado River Gila robusta complex (Holden and Stalnaker, 1970). The fish primarily exists in relatively inaccessible canyon areas, and it apparently was rare in most historical collections (Valdez and Clemmer, 1982). A recovery plan for G. cypha was prepared by the US Fish and Wildlife Service (USFWS, 1990, unpubl.), which has sought information for evaluating past and present status of the fish and for designing recovery efforts. However, recovery programs for G. cypha, and its congener, G. elegans, have suffered from a lack of knowledge about taxonomic status, extent of hybridization, distribution and abundance, and especially population trend data (USFWS, 1990, unpubl.). Although much information has been obtained about other rare Colorado River fishes

Disciminating Gila Robusta and Gila Cypha: Risk Assessment and the Endangered Species Act

Disciminating Gila Robusta and Gila Cypha: Risk Assessment and the Endangered Species Act

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...