Migrating Mormon Crickets, Anabrus simplex (Orthoptera: Tettigoniidae), as food for stream fishes

Migrating bands Mormon crickets ( Ananbrus simplex ) were observed crossing the Green and Yampa rivers in Dinosaur National Monument, Colorado and Utah, in 1986 and 1987. Swimming crickets were swept downstream and eaten by four- endemic and seven introduced fish species. Included were two endangered fishes, Colorado squawfish ( Ptychocheilus lucius ) and humpback chub ( Gila cypha ). Direct and indirect effects to aquatic food webs associated with application of pesticides for Mormon cricket control may pose a threat to these fishes and to man.     

Habitat characteristics of leatherside chub ( Gila copei ) at two spatial scales

Populations of leatherside chub ( Gila copei ), a little-known species native to the eastern Great Basin, have declined and their distribution has become fragmented. To determine habitat requirements and possible factors responsible for population decline, we quantified macrohabitats and microhabitats occupied by leatherside chub. Macrohabitat was surveyed at 59 sites in the Sevier River drainage of south central Utah, and microhabitats occupied by leatherside chub were measured at 3 locations spanning the species latitudinal range. Characteristics of points in the stream where leatherside chub occurred were compared to points where they did not occur. Abundance of brown trout ( Salmo trutta ) and elevation were weakly negatively correlated with leatherside chub distribution on a macrohabitat scale. Microhabitats occupied by leatherside chub were characterized by low water velocities (2.5-45 cm sec -1 ), intermediate water depths (25-65 cm), and low percent composition of sand-silt or gravel substrates. This study suggests that the presence of introduced brown trout may have led to the decline of leatherside chub.     

Habitat use of leatherside chub ( Gila copei ) in the presence of predatory brown trout ( Salmo trutta )

The objectives of this study were to (1) examine distribution and habitat use of leatherside chub ( Gila copei ) in a creek with high densities of predatory brown trout ( Salmo trutta ), and (2) compare study results with published accounts of leatherside chub habitat use in streams with few or no brown trout. A 14-km section of Diamond Fork Creek, Utah, was point-shocked to determine macrohabitat (main channel and lateral habitat) and microhabitat (current, depth, substrate, and cover) use of leatherside chug. At the macrohabitat level, leatherside chub were most common in lower reaches of Diamond Fork Creek where the channel was braided and lateral habitats (cutoff pools and backwaters) were abundant. Only a single leatherside chub was found in the main channel of Diamond Fork. Investigations in other systems lacking brown trout indicated that leatherside chub occupy main channel habitats. At the microhabitat level, we found significant positive associations between presence of leatherside chub and both habitat depth and silt. In addition, we found a significant negative association between presence of leatherside chub and number of brown trout. Our results suggest predation by brown trout may limit leatherside chub to lateral habitats that could provide refugia against predation. The introduction of brown trout to systems with little lateral habitat could have serious effects on persistence of resident leatherside chub populations.     

Asian tapeworm ( Bothriocephalus acheilognathi ) in native fishes from the Little Colorado River, Grand Canyon, Arizona

Examination of gastrointestinal tracts of native cyprinids from the Little Colorado River (LCR) in Grand Canyon, Arizona, 1990-1994, revealed varying rates of prevalence and infrapopulation levels of Asian tapeworm ( Bothriocephalus acheilognathi ). Mean prevalence was 28% (range 0-78%) in humpback chub ( Gila cypha ) and 8% (range 0-46%) in speckled dace ( Rhinichthys osculus ), with infrapopulations as high as 46 and 28, respectively. We also note Asian tapeworm infection of nonnatives common carp ( Cyprinus carpio ), fathead minnow ( Pimephales promelas ), and plains killifish ( Fundulus zebrinus ) from the LCR. Reported pathogenic and chronic effects of this cestode to its definitive hosts add concern for the status of the Grand Canyon population of the federally endangered humpback chub. The rapidity which Asian tapeworm has spread to different drainages of the Colorado River Basin likely portends an eventual cosmopolitan basin distribution in lower elevations suitable to the parasite's thermophilic life history. Such biotic changes must be considered among the most serious threats to conservation and recovery of native fish populations.     

A comparison of mosquito consumption and prey selection between least chub ( Iotichthys phlegethontis ) and western mosquitofish ( Gambusia affinis )

We compared mosquito consumption and prey selection between least chub ( Iotichthys phlegethontis ) and western mosquitofish ( Gambusia affinis ) to determine the potential of least chub as an indigenous replacement for mosquito control in Utah. Mosquito consumption was compared between the 2 species in 2 experiments. The first tested consumption at 3 ratios of pupae and larvae ( Culex sp.; 1:3, 3:4, and 1:1), and the second tested consumption at varying densities of larvae (967 larvae ? m–3 , 1354 larvae ? m–3 , and 2258 larvae ? m–3 [30, 42, and 70 larvae per 31-L tank, respectively]). Western mosquitofish consumed more mosquitoes at lower pupae-to-larvae ratios than least chub, but least chub consumed more mosquitoes as the ratio of pupae to larvae increased. Western mosquitofish consumed significantly more larvae than least chub at all densities. Prey selection was compared between least chub and western mosquitofish, either individually or in intraspecific pairs, when the fish were fed equal abundances of 3 prey items: mosquito larvae, Daphnia magna , and midge larvae ( Chironomid sp.). Least chub consumed significantly fewer total prey items for both the 1- and 2-fish trials; western mosquitofish consumed significantly more individuals of each prey type except for Daphnia magna in the 1-fish trials. Least chub and western mosquitofish demonstrated no selection for prey items, indicating that both fish would consume mosquito larvae at rates relative to abundance. Feeding habits demonstrated in this study indicated that least chub could be a potential replacement for western mosquitofish for mosquito control; however, field studies should be conducted to assess the ability of both species to control mosquitoes in a natural setting.     

Age, growth, and food habits of tui chub, Gila bicolor, in Walker Lake, Nevada

At Walker Lake, Nevada, tui chub were collected 1975–1977 for analysis of age, growth rate, and food habits. The fork length (FL) – scale radius (SR) relationship was linear and described by the equation FL = 4.44 + 3.17 (SR). Age I, II, III, and IV chub were 116, 176, 218, and 242 mm fork length, respectively. Maximum longevity was six years. The length weight relationship was defined by the log transformed linear equation log weight = - 4.65 + 2.93 (log FL). Chub collected from pelagic regions ate mostly zooplankton, whereas chub collected from littoral areas had a diet of zooplankton and benthic organisms.         

Parasites of the woundfin minnow, Plagopterus argentissimus , and other endemic fishes from the Virgin River, Utah

Two hundred woundfin minnows, Plagopterus argentissimus , from four sites along the Virgin River, Utah, were examined on two dates during summer 1985. The foreguts of 211 woundfin and variable numbers of other fishes from the Virgin River near Beaver Dam Wash, Arizona, and Mesquite, Nevada, were examined for cestodes on four dates throughout 1979. Seven parasites were found in P. argentissimus: Posthodiplostomum minimum (metacercariae), Diplostomum spathaceum (metacercariae), Bothriocephalus acheilognathi, Gyrodactylus sp., Lernaea cyprinacea, Trichodina sp., and Ichthyophythirius multifiliis . Fungal infections were noted on two fish during the study. Seventeen Virgin River roundtail chub, Gila robusta seminuda, were examined from two of the four sites in 1985 and 64 specimens from Beaver Dam Wash were examined in 1979. Gila robusta seminuda was infected with Posthodiplostomum minimum (metacercariae) and Bothriocephalus acheilognathi, the Asian fish tapeworm. This cestode probably gained entrance into the ichthyofauna of the Virgin River from red shiners, Notropis lutrensis, and has the potential of being very detrimental to the endemic and endangered fishes of the Virgin River. Parasite loads were correlated with water quality and habitat disturbance, with highest number and frequency occurring in "disturbed" sites. Low river flows and increased total dissolved solids appear to be associated with a higher parasite frequency and mean number in fishes of the Virgin River. These data represent the first known published records for parasites of the woundfin minnow and Virgin River roundtail chub.     

Spawning of the least chub ( Iotichthys phlegethontis )

The least chub, lotichthys phlegethontis (Cope), a relict fish in Utah, spawned successfully under laboratory conditions.     

Effects of temperature on the survival and growth of age-0 least chub ( Iotichthys phlegethontis )

Larval and juvenile stages of many fishes require nursery habitats that provide optimal conditions for growth. Loss or degradation of these habitats limits recruitment, causing population and species declines. Least chub ( Iotichthys phlegethontis ), an endemic cyprinid in the Bonneville Basin, is currently restricted to a few spring complexes in Utah. This species utilizes the warm shallow spring margins as spawning and rearing habitat throughout the summer. This study was conducted to determine effects of temperature on survival and growth of age-0 least chub to understand the importance of temperature in selection of spring margins as rearing habitat. Age-0 least chub were exposed to 5 temperatures (14°C, 17°C, 21°C, 24°C, and 27°C) for 112 days. Growth rates varied significantly with temperature except at 17°C and 27°C, and growth rates were highest at 21°C ( P < 0.001). Maximum growth rate for age-0 least chub, estimated from a 2nd-order polynomial regression, would occur at 22.3°C. These thermal requirements indicate the importance of warm rearing habitats in producing strong year classes and viable populations. However, warm spring margins also enable western mosquitofish, a nonnative competitor and predator of least chub, to thrive in these spring habitats. Broad thermal limits of the least chub suggest that it could persist at cooler temperatures, which would reduce the viability of western mosquitofish populations.     

Thermal tolerances and preferences of fishes of the Virgin River system (Utah, Arizona, Nevada)

Critical thermal maxima (CTM) and thermal preferenda of the common fishes of the Virgin River were examined. Differences in final temperature preferenda and CTM for species with low thermal lability (speckled dace, spinedace, roundtail chub) correspond well with differences in their distribution and abundance in the river. These species shifted their acute thermal preferences relatively little as acclimation temperature increased. For thermally labile species (woundfin, red shiner, desert sucker, and flannelmouth sucker), the final preferendum is a less precise indicator of probably distribution. The woundfin, an endangered fish, has a high CTM (39.5 C at 25 C acclimation) and a labile species preferendum (slope nearest 1) compared to other species in the system. The introduced red shiner likewise has a high CTM and a labile acute preferendum. In cooler temperatures, its acute preferendum shifts more rapidly than does that of the woundfin. At higher temperatures (above 15 C), the red shiner does not shift its acute preferendum as rapidly as does the woundfin. The red shiner, however, has a higher final preferendum. For thermally labile species, influence of acclimation temperature on mean preferendum, together with CTM, provides a better insight into distributional relationships within the system.     

New mites from the Yampa Valley (Acarina: Cryptostigmata: Oribatulidae, Passalozetidae)

A study was made of the soil mites from under different vegetative types near a coal - burning power plant in the Yampa Valley near Hayden, Colorado. The following new species of oribatids were found: Zygoribatula apletosa n.sp., Multoribates haydeni n.sp., Paraphauloppia cordylinosa n.sp., Passalozetes moniles n.sp. &nbsp;     

Observations on the reproduction and embryology of the Lahontan tui chub, Gila bicolor, in Walker Lake, Nevada

Various aspects of the reproduction and embryology of Walker Lake Lahontan tui chub, Gila bicolor , were investigated during the spring&ndash;summer period of 1976, 1977, and 1981. Tui chub were found to spawn in littoral regions of the lake beginning in late May or early June. Early in the season male chub substantially outnumbered females over the spawning grounds, with a normal 1:1 sex ratio gradually approached as the season progressed. The developmental period between fertilization to hatch-out was shortened by increases in water temperature. Selected stages of embryonic development are described from egg fertilization through post-hatch.     

Home-range fidelity and use of historic habitat by adult Colorado pikeminnow ( Ptychocheilus lucius ) in the White River, Colorado and Utah

Twelve wild adult Colorado pikeminnow ( Ptychocheilus lucius ), captured in the tailwaters of Taylor Draw Dam on the White River, Colorado, were implanted with radio transmitters and their movement patterns monitored from 1992 to 1994. The spawning migration of these fish was extensive. In 1993, the only full year of the study, the fish migrated an average of 658 km from the White River to spawning sites in the Yampa or Green rivers and back to the White River. Eight of these fish were translocated in the river upstream of the dam in April 1993. These fish and the 4 others below the dam remained in the river until May 1993. All 12 had migrated down the White River to spawning sites in the Green and Yampa rivers by July 1993. The fish that were located above the dam successfully passed over the dam during their downstream migration. Seven fish migrated upstream toward the Yampa River Canyon spawning site and 5 migrated downstream toward the Green River Desolation/Gray Canyon spawning site. Five of 7 Yampa River fish were found at the spawning site. The other 2 were found 5-8 km downstream of the site. One of 5 Green River fish was found at the spawning site, the other 4 between 16 and 62 km upstream of the site. All fish migrated back to the White River by August 1993 and were found near the dam by October 1993. Two fish were recaptured and translocated above the dam in September 1993. Five fish were located below the dam and 2 above the dam in April 1994. By July 1994 seven of the same fish that had migrated toward the Yampa River in 1993 were found at the Yampa Canyon spawning site. At the same time, 3 of 5 fish that migrated toward the Green River in 1993 were found at the Desolation/Gray Canyon spawning site. This included 2 fish that had been found upstream of the site in 1993. The 12 fish traveled an average of 6 km d -1 (range: 4-10 km d -1 ) during the migration period from May through October 1993. Generally, fish moved faster to the spawning site than back from the site to the White River. These fish moved very little within their home ranges in the White River. Six fish tagged in 1992 moved only 0.1-2.3 km in the tailwater reach below Taylor Draw Dam from September 1992 through April 1993. All fish, after their spawning runs, had moved up to or near the dam by October 1993. These fish were not tracked again until April 1994. Their movement patterns in April 1994 were similar to those observed in April 1993. The greatest amount of fish movement in the White River was displayed by the 8 fish placed above Taylor Draw Dam in April 1993 and the 2 placed in Kenney Reservoir in September 1993. They moved 1.1-40.6 km in the river before and after their spawning migration in spring and autumn 1993. These spawning migrations suggest that adult Colorado pikeminnow in the White River were recruited from both Green and Yampa river spawning populations and were presumably imprinted to these respective spawning sites. Those fish placed above Taylor Draw Dam established home ranges in habitats previously occupied by Colorado pikeminnow before the dam was completed. They remained there until they migrated downstream during the spawning period. Although we did not study fish passage, our study demonstrates that adult Colorado pikeminnow will use habitat if access is provided. Translocation of wild adult fish into historic but unoccupied habitats may be a valuable recovery option.     

Esox lucius (Esocidae) and Stizostedion vitreum (Percidae) in the Green River basin, Colorado and Utah

Northern pike, Esox lucius , stocked in the Yampa River in 1977, invaded the mainstream Green River by 1981 and subsequently increased in range and abundance. The speed of this invasion is indicated by two recaptured pike that moved 78 and 110 km, respectively, downstream in about one year. Pike stomachs (n = 123) were usually empty (54.5%), but some contained fish (43%) and nonfish items (2.4%). Red shiner, Notropis lutrensis , and fathead minnow, Pimephales promelas , predominated among the 12 fish species eaten. Walleye, Stizostedion vitreum , presumably introduced to the Green River drainage in the 1960s, was widely distributed but low in abundance. Most of 61 adult walleye stomachs contained food (60.7%) ; of 6 fish species eaten, channel catfish, lctalurus punctatus , and fathead minnow were most frequently consumed. Northern pike and walleye were captured in habitats occupied by endangered Colorado River fishes, particularly Colorado squawfish, Ptychocheilus lucius . Predation on endangered fishes was not detected, but northern pike and walleye consumed at least three other native fishes. The northern pike may pose a threat to endangered fishes due to its population expansion, piscivory, and resource sharing. Diets of northern pike and walleye species should be further evaluated if their abundance increases.     

Archaeological record of native fishes of the lower Colorado River: how to identify their remains

Archaeological sites in the Salton Basin of southeastern California and along the lower Colorado River provided opportunities to determine which fish species were present prior to extirpations, environmental degradation, and the recession of Lake Cahuilla. These remains also represent the fishes exploited by Native Americans. Bonytail ( Gila elegans ), razorback sucker ( Xyrauchen texanus ), Colorado pikeminnow ( Ptychocheilus lucius ), striped mullet ( Mugil cephalus ), and machete ( Elops affinis ) have been recovered from 117 sites in the Salton Basin, once filled by the Colorado River forming Lake Cahuilla. Bonytail and razorback sucker comprise nearly 99% of the remains. Along the lower Colorado River itself, fragmentary elements of bonytail, razorback sucker, Colorado pikeminnow, and roundtail chub ( G. robusta ) have been recovered, documenting a disappearing native fish fauna. Anatomical details are described that permit identification of diagnostic materials commonly recovered during archaeological excavations.     

Optimal temperatures for growth and upper thermal tolerance of juvenile northern leatherside chub

We examined optimal temperatures for growth and the upper thermal tolerance of juvenile northern leatherside chub ( Lepidomeda copei ). We conducted 2 experiments using the acclimated chronic-exposure method to estimate optimal temperature for growth of age-0 northern leatherside chub (range 12.8–28.3 °C). Upper thermal tolerance was estimated using the critical thermal maximum (CTM) and upper incipient lethal temperature (UILT) methods for fish acclimated at 15, 18, 23, and 28 °C. We also measured stream temperatures in Yellow Creek, Summit County, Utah, during July–August 2006 to compare our results to actual summer stream temperatures. Survival in growth tests was not significantly different between treatment temperatures in either experiment (P > 0.098). The optimal temperature for growth in the 1st trial estimated from the 2nd-order polynomial regression was 23.0 °C, falling outside the range of experimental temperatures (12.8–22.2 °C). The estimated optimal temperature for growth in the 2nd trial was 23.2 °C. In the upper thermal tolerance tests, juvenile northern leatherside chub had CTM values between 29.6 and 35.0 °C; CTM values increased as acclimation temperature increased. Upper incipient lethal temperatures (LT50) ranged from 26.5 to 30.2 °C, increasing with acclimation temperature. Summer stream temperatures in Yellow Creek had a lower mean (14.0–18.1 °C) than did the optimal temperature for growth determined in these studies, but these temperatures exhibited diel fluctuations as large as 15.7 °C.     

Melanism in endangered Mohave tui chub Siphateles bicolor mohavensis Snyder 1918 (Cypriniformes: Cyprinidae)

Although melanism has been reported in a wide variety of taxa, the presence of melanic individuals is relatively rare in fishes. Melanism in Mohave tui chub ( Siphateles bicolor mohavensis ), an endangered endemic of the Mojave Desert in California, is reported from 2 of 4 surveyed populations. The typical body color varies from dark brown to olive brown dorsally and is whitish ventrally; sides are silvery or golden, and fins are pale yellow to dusky red. While conducting population censuses in 2007&ndash;2008, we found 4 melanic Mohave tui chubs from 2 of 4 surveyed habitats. Two of 1049 fish (0.19%) handled from Lake Tuendae (Mojave National Preserve) and 2 of 1516 fish (0.13%) handled from Bud&rsquo;s Pond (Camp Cady Wildlife Area) were melanic. Melanic individuals were dorsally black, gradually fading into blackish brown on the sides; the sides had a golden or silvery sheen, and fins were blackish brown. Though the occurrence of melanism is very rare, it may reflect underlying genetic variation, which is of particular interest to the conservation of rare and endangered species. Aunque se han reportado casos de melanismo en varios taxa, son relativamente poco frecuentes los individuos mel&aacute;nicos entre los peces. Se reporta la presencia de melanismo en 2 de las 4 poblaciones estudiadas de la carpa tui del Mohave ( Siphateles bicolor mohavensis ), una especie end&eacute;mica en peligro de extinci&oacute;n del Desierto de Mojave en California. El color t&iacute;pico de su cuerpo var&iacute;a entre caf&eacute; oscuro y caf&eacute; olivo en el dorso, con el abdomen blancuzco, los costados dorados o plateados y las aletas entre amarillo claro y rojo viol&aacute;ceo. Encontramos 4 carpas tui del Mohave mel&aacute;nicas en 2 de los 4 h&aacute;bitats estudiados al hacer censos poblacionales entre 2007 y 2008. Fueron mel&aacute;nicos 2 de los 1049 peces (0.19%) y 2 de los 1516 peces (0.13%) examinados en el lago Tuendae (Mojave National Preserve) y en el estanque de Bud (Camp Cady Wildlife Area), respectivamente. Los individuos mel&aacute;nicos ten&iacute;an el dorso de color negro que gradualmente se convert&iacute;a en caf&eacute; negruzco hacia los costados, los cuales ten&iacute;an un brillo dorado o plateado. Las aletas eran color caf&eacute; negruzco. Aunque el melanismo es relativamente poco com&uacute;n, podr&iacute;a reflejar la variaci&oacute;n gen&eacute;tica subyacente, la cual es de especial inter&eacute;s para la conservaci&oacute;n de especies raras y en peligro de extinci&oacute;n.     

Status and distribution of the Fish Creek Springs tui chub, Gila bicolor euchila

The Fish Creek Springs tui chub, Gila bicolor euchila , is present in large numbers throughout its native habitat in spite of extensive man-caused habitat disturbance. This subspecies occurs further downstream in Fish Creek than previously reported. &nbsp;     

Trypanoplasma atraria sp. n. (Kinetoplastida: Bodonidae) in fishes from the Sevier River drainage, Utah

A total of 181 fishes belonging to 10 species were captured near Richfield, Utah, and examined for parasites. A new species of hemoflagellate, Trypanoplasma atraria sp. n., was observed in 3 species: Utah chub ( Gila atraria [Girard]), redside shiner ( Richardsonius balteatus [Richardson]), and speckled dace ( Rhinichthys osculus [Girard]). Seven other species of fishes examined in the study area were negative for T. atraria sp. n. The salmonid leech, Piscicola salmositica (Meyer), collected in the same area harbored developmental stages of Trypanoplasma , suggesting a possible leech vector for the hemoflagellate. Characteristics of Trypanoplasma atraria sp. n. place it near T. salmositica , but the new species is twice as large.     

Beaver herbivory of willow under two flow regimes: a comparative study on the Green and Yampa rivers

The effect of flow regulation on plant-herbivore ecology has received very little attention, despite the fact that flow regulation can alter both plant and animal abundance and environmental factors that mediate interactions between them. To determine how regulated flows have impacted beaver ( Castor Canadensis ) and sandbar willow ( Salix exigua ) ecology, we first quantified the abundance and mapped the spatial distribution of sandbar willow on alluvial sections of the flow-regulated Green River and free-flowing Yampa River in northwestern Colorado. We then established 16 and 15 plots (1 m x 2.7 m) in patches of willow on the Green and Yampa Rivers, respectively, to determine whether rates of beaver herbivory of willow differed between rivers (Green versus Yampa River), seasons (fall-winter versus spring-summer), and years (spring 1998-spring 1999 versus spring 1999-spring 2000). Areal extent of willow was similar on each river, but Green River willow patches were smaller and more numerous. Beavers cut more stems during fall and winter than spring and summer and cut over 6 times more stems (percentage basis) on the Green River than on the Yampa River. We attribute the between-river difference in herbivory to higher availability of willow, greater beaver density, and lower availability of young Fremont cottonwood ( Populus deltoids subsp. wislizenii ; an alternative food source) on the Green River. Flow regulation increased willow availability to beaver by promoting the formation of island patches that are continuously adjacent to water and feature a perimeter with a relatively high proportion of willow interfacing with water.