Aquatic vertebrate assemblages of the Upper Clear Creek Watershed, California

We sampled streams in the Upper Clear Creek Watershed in northwestern California in fall 2004 and fall 2005 to document assemblages of aquatic vertebrates and to provide resource managers with information on the importance of these assemblages in terms of regional biodiversity. We used single-pass backpack electrofishing to sample 15 sites in fall 2004 and the same 15 sites plus 4 new sites in fall 2005. We captured 10 fish taxa and 2 species of larval amphibians. Seven of the fish taxa were native species. Of the exotic species, only brook trout ( Salvelinus fontinalis ) occurred at more than 1 site. Ordinations by nonmetric multidimensional scaling indicated a gradient from sites with rainbow trout ( Oncorhynchus mykiss ), Pacific giant salamander ( Dicamptodon tenebrosus ), and tailed frog ( Ascaphus truei ) to sites dominated by riffle sculpin ( Cottus gulosus ), California roach ( Hesperoleucas symmetricus ), and Sacramento sucker ( Catostomus occidentalis ). The gradient in species composition was associated with changes in elevation, gradient, discharge, and substrate. The Upper Clear Creek Watershed represents a unique area of overlap between the North Coast California amphibian fauna and the Central Valley fish fauna with a notable paucity of exotic fishes and amphibians. Preservation of the integrity of native aquatic assemblages is an important goal for aquatic resource management in the region; our results provide a critcial baseline to gauge future management actions.     

Status and life history notes on the native fishes of the Alvord Basin, Oregon and Nevada

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Humpback chub ( Gila cypha ) in the Yampa and Green rivers, Dinosaur National Monument, with observations on roundtail chub ( G. robusta ) and other sympatric fishes

We evaluated distribution, habitat use, spawning, and species associations of the endangered humpback chub ( Gila cypha ) in the Yampa and Green rivers, Dinosaur National Monument, from 1986 to 1989. Adult and juvenile humpback chub were captured in high-gradient reaches of Yampa and Whirlpool canyons where they were rare ( n = 133, G. robusta ) were widely distributed in eddies, pools, runs, and riffles. Humpback chub ( n = 39) and roundtail chub ( n = 242) in reproductive condition were sympatric in eddy habitats during the 5-6 week period following highest spring runoff. River temperatures at this time averaged about 20 C. Nonnative channel catfish ( Ictalurus punctatus ) were abundant in eddies yielding humpback and roundtail chubs, suggesting a potential for negative interactions between the native and introduced fishes.     

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.     

Native plant community composition and genetic diversity associated with long-term weed invasions

Many studies have assessed genetic changes in exotic plant species in their native and introduced ranges, but none have focused on genetic variation in native plant species in response to exotic invasion. We examine characteristics of native plant communities within and outside old (> 25 year) invasions of Acroptilon repens (Russian knapweed) and Cardaria draba (hoary cress). We also document genetic variability of 4 native grass populations ( Hesperostipa comata [needle and thread], Achnatherum hymenoides [Indian ricegrass], Sporobolus airoides [alkali sacaton], and Poa secunda [Sandberg bluegrass]) from 2 areas: adjacent to and within weed invasions. Native plant species richness and diversity did not differ between invaded and noninvaded areas. Inter-simple sequence repeat (ISSR) analysis of individual native perennial grasses of each of the 4 species suggests that populations exposed to long-term coexistence with exotics may differ from adjacent noninvaded populations. We suggest that future research efforts should focus on intraspecific diversity of native plant species to identify possible candidates for restoration following weed control.     

Spatial distribution of ichthyofauna in the northern Alboran Sea (western Mediterranean)

This study describes the four main demersal fish assemblages identified along the continental shelf and slope (30–800 m depth) of the northern Alboran Sea (western Mediterranean), based on the analysis of the MEDITS (International bottom trawl survey in the Mediterranean) 12-year data series. We collected 186 fish species belonging to three classes, 24 orders and 69 families. Taxonomically, the order Perciformes was the most diverse, represented by 18 families and 58 species. Each assemblage had particular characteristics of abundance, biomass, mean fish weight and species richness. The geographical differences associated with the distribution of some species occurred within shelf assemblages. The middle slope was characterised by the highest similarity between samples, probably due to its lower environmental variability compared to that of the other assemblages.     

Planted grasslands and native sod prairie: equivalent habitat for grassland birds?

Little is known about how avian relationships to tracts of native sod prairie compare with avian relationships to single and multiple species of cool- and warm-season grassland plantings. We compared grassland bird species richness and density in 5 grassland cover types ( n = 97) in the tallgrass prairie region of eastern South Dakota and western Minnesota, 2001–2004. Grassland bird species richness was significantly higher in native sod prairies than it was in all planted cover types except warm-season mixes. Grasslands dominated by exotic species did not support as many grassland bird species or have species densities as high as grasslands containing native species. Intermediate wheatgrass monotypes and cool-season mixes comprised of exotic species contained 40%–60% fewer grassland bird species than native sod prairie. Bobolink ( Dolichonyx oryzivorus ) density was 68% and 51% lower in intermediate wheatgrass monotypes and cool-season mixes, respectively, than it was in switchgrass monotypes. Clay-colored Sparrow ( Spizella pallida ) density was 75%–91% higher in native sod prairies than it was in any other cover type. Savannah Sparrow ( Passerculus sandwichensis ) density was 72% higher in native prairie than it was in grasslands dominated by exotic species. We recommend incorporating a diversity of native plant species into grassland plantings for biomass fuels or wildlife, rather than using monotypes or exotic species, to provide habitat for grassland birds. Although replacing croplands with planted grasslands would benefit grassland bird populations, we caution that replacing existing native sod tracts with planted grasslands would be detrimental to populations of several grassland bird species.     

Lahontan cutthroat trout ( Oncorhynchus clarki henshawi ) spawning and downstream migration of juveniles into Summit Lake, Nevada

The only remaining self-sustaining native population of lacustrine Lahontan cutthroat trout ( Oncorhynchus clarki henshawi ) not affected by nonnative salmonids is in Summit Lake, Humboldt County, Nevada. Annual spawning runs in 1993 and 1994 were monitored at a fish trap on Mahogany Creek, the only spawning tributary for Summit Lake. Number of spawners was similar in both years, with 1290 upstream migrants observed in 1993 and 1255 in 1994. In 1993, 137 postspawners (10.6% of upstream migrants) returned to the lake, and in 1994, 434 postspawners (34.6% of upstream migrants) returned downstream through the fish trap. Two distinct groups of subadult Lahontan cutthroat trout were observed moving downstream in 1994. The first group passed downstream between 27 April and 29 July and included 1188 fish (average fork length = 90 mm). Between 1 August and 31 October, 1160 fish (average fork length = 42 mm) moved downstream. Size differences of these 2 groups suggest that the 1st group comprised fish that had overwintered in Mahogany Creek, while the 2nd group were probably young-of-the-year.     

Leafhopper assemblages on native and reseeded grasslands in southwestern Montana

Using sweep samples, we surveyed leafhoppers (Homoptera: Cicadellidae) on grassland sites in the Gallatin Valley of Montana during 1988 and 1991. We sampled 12 sites representing 2 habitat types defined by their dominant plant species in an undisturbed state ( Stipa comata / Bouteloua gracilis and Festuca idahoensis / Agropyron spicatum ). At half of the sites the native plant communities were present, whereas the remainder had been reseeded with either Agropyron spicatum (to replace the S. comata / B. gracilis assemblage ) or Bromus inermis (to replace the F. idahoensis / A. spicatum assemblage). We found at least 66 species of leafhoppers among 44,428 adults collected. Seven taxa comprised 83% of all individuals collected: Doratura stylata (26%), Ceratagallia spp. (18%), Endria inimica (17%), Orocastus perpusillus (7%), Sorhoanus spp. (6%), Athysanella spp. (5%), and Psammotettix lividellus (4%). Sites with similar vegetation had broadly similar leafhopper assemblages, and assemblages differed most between the relatively xeric Stipa comata / Bouteloua gracilis sites and the more mesic sites dominated by Bromus inermis . The composition of a leafhopper assemblage at a site tended to be more similar to those on noncontiguous sites with the same overall vegetation than to those on contiguous sites with different vegetation. These patterns are likely related to the fact that many Cicadellidae are host specialists. In fact, variation in abundance of some of the most common leafhopper taxa on our sites was correlated with the percent cover of their known host plants. Our analyses of the leafhopper assemblages generally support the contention that terrestrial plant associations are among the more useful indicators of insect community composition.     

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.     

Aspects of the biology of the flathead chub ( Hybopsis gracilis ) in Montana

Mature flathead chubs ( Hybopsis gracilis ) were present in mid - July and mid - August collections from the Musselshell River, Montana. The estimated numbers of mature eggs present in eight females were 360–753 per female. The smallest mature female and male collected were 113 and 123 mm in total length, respectively. The male to female sex ratio in collections was about 1:1. Only small differences were detected among the length – weight relationships of males and females and samples taken from various seasons and localities in Montana. Observations on size groups, fish associates, and habitat characteristics of flathead chubs are presented.         

Bird use of riparian vegetation along the Truckee River, Califonia and Nevada

The Truckee River in California and Nevada is subject to diverse water regimes and a corresponding variety of flow rates. Original riparian vegetation has been altered by these variable flow rates and by a variety of human uses resulting in loss of native riparian vegetation from its historic extent. We conducted bird surveys along the Truckee River during spring 193 to (1) determine relationships between birds and the present vegetation; (2) determine the importance of different vegetation types to sensitive bird species that have declined recently in the western United States due to competition from exotic plant species, cowbird ( Molothrus ater ) parasitism, reduction in nesting habitat, or other unidentified reasons; and (3) establish a monitoring program and collect baseline data for future comparisons. The most frequently detected bird species throughout the study was the Brown-headed Cowbird. The greatest number of bird species (98 of 116) was found in the native mixed willow ( Salix spp.) riparian scrub vegetation type. We recommend protecting the remaining native riparian vegetation types for bird habitat along the Truckee River.     

Vertical distribution of adult fish in Pyramid Lake, Nevada

Inshore and limnetic vertical distribution of adult fish in Pyramid Lake, Nevada was determined from late spring to early fall 1977. The benthic (23 m) inshore area exhibited a relatively diverse composition of five species, while the inshore surface and offshore limnetic zones were composed of over 98 percent tui chubs ( Gila bicolor ). Vertical fish distribution was associated with temperature and zooplankton distribution.     

Plant species richness at different scales in native and exotic grasslands in southeastern Arizona

Species richness in Madrean mixed-grass prairies dominated by native or exotic species in southeastern Arizona was characterized at the community and point scales using ten 1-m 2 quadrats nested within each of eight 1000-m 2 plots. In the 1000-m 2 plots average richness was significantly higher in oak savanna (OS, 121.0 species) than in exotic grassland on mesa tops (EMT, 52.0 species), whereas native grassland on mesa slopes (NMS, 92.5 species) and native grassland on mesa tops (NMT, 77.0 species) did not differ significantly in richness from OS or EMT. When richness was partitioned by life form, EMT was notably poorer than other community types in species of perennial grasses, perennial herbs, and summer annuals. In the 1-m 2 quadrats, OS (21.2 species), NMS (20.9 species), and NMT (20.7 species) were significantly richer than EMT (5.9 species). Cover in 1-m 2 plots was significantly higher in EMT than in NMT, NMS, or OS. Species richness at the point scale showed a unimodal relation to canopy cover, with cover accounting for 30% of the variation in number of species in 1-m2 quadrats. Competitive exclusion and allelopathy have perhaps limited species richness at the point scale in exotic grassland. There was no evidence of a species-pool effect between point and community scales, but such an effect between community and landscape scales was supported. Madrean mixed-grass prairies are landscapes with high species richness in comparison to other grassland types in North America, providing a large pool of potential colonizing species at the community scale. Beta-diversity (between communities) within the landscape of the Appleton-Whittell Research Ranch was consequently high despite a relative lack of habitat diversity.     

Geographic patterns of ground-dwelling arthropods across an ecoregional transition in the North American Southwest

We examined the biogeographic patterns of ground-dwelling arthropod communities across a heterogeneous semiarid region of the Southern Rio Grande Rift Valley of New Mexico. Our 3 sites included portions of 5 ecoregions, with the middle site a transition area where all ecoregions converged. We addressed the following 3 questions: (1) Do the species assemblage patterns for ground arthropods across habitats and sites conform to recognized ecoregions? (2) Are arthropod assemblages in distinct vegetation-defined habitats within an ecoregion more similar to each other or to assemblages in similar vegetation-defined habitats in other ecoregions? (3) Is there a detectable edge effect with increased arthropod diversity in the area of converging ecoregions? We encountered 442 target arthropod species from pitfall traps operating continuously for 7 years over a series of different habitats at each of the 3 sites. We examined geographic distributions of spider and cricket/grasshopper species in detail, and they showed affinities for different ecoregions, respectively. Each habitat within a study site supported a unique overall arthropod assemblage; nevertheless, different habitats at the same site were more similar to each other than they were to similar habitats at other sites. Overall arthropod species richness was greatest in the area where all 5 ecoregions converged. Arthropod species and their geographic distributions are poorly known relative to vascular plants and vertebrate animals. Findings from this research indicate that ecoregional classification is a useful tool for understanding biogeographic patterns among arthropods.     

Factors influencing fish assemblages of a high-elevation desert stream system in Wyoming

Seven fish species were found in the Bitter Creek drainage of southwest Wyoming, but only speckled dace ( Rhinichthys osculus ), flannelmouth sucker ( Catostomus latipinnis ), and mountain sucker ( Catostomus platyrhynchus ) were indigenous. No relationships were found between fish standing stocks and habitat features, but species richness was related to elevation and stream width. No fish were found above an elevation of 2192 m. Only the most downstream study read had more than three species present. Two indigenous species, speckled dace and mountain sucker, and a nonnative species, fathead minnow ( Pimephales promelas ), were predominant fishes in the drainage. These three species withstand intermittent stream flows that are common in the drainage.     

Present effects of past wildfires on the diets of stream fish

We investigated present indirect effects from a decade-old burn on the diets of stream fish. Based on soil instability and burn patterns from a 12–14-year-old wildfire complex, we separated 9 streams into 3 conditions: unburned, burned, and burned/scoured (i.e., experiencing a massive scour event 1 year post-burn). In the streams, we measured light levels and water temperatures, and we estimated fish density and biomass. We removed the digestive tracts from 9–15 rainbow trout ( Oncorhynchus mykiss ) from each stream and used a gravimetric procedure to analyze gut contents. Canopy cover development may dictate the composition of dietary items. Greater amounts of aquatic invertebrates and inorganic material were found in trout from streams with reduced overhead canopy. Further, these streams had lower amounts of terrestrial invertebrates and organic materials in the diets of fish. Although trout abundance was not different among the stream treatments, fire-induced, indirect effects on fish diets were still evident more than a decade after the burn. This suggests that recovery rates for trout assemblages may take longer than predicted and may depend on riparian recovery.     

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.     

Relationship of diurnal habitat use of native stream fishes of the eastern Great Basin to pPresence of introduced salmonids

Introduced brown trout, Salmo trutta , are common to many streams of western North America. However, the ecological interactions between brown trout and native stream fishes are not well understood, particularly the nature and extent of antipredator responses of native species. We examined the effects of brown trout presence on diurnal habitat use by 2 small native fishes at a mesohabitat scale (e.g., pool, riffle, run, backwater, etc.). Adult and juvenile southern leatherside chub ( Lepidomeda aliciae , formerly Gila copei ) and juvenile mountain sucker ( Catostomus platyrhynchus ) were located in main channel pools in the absence of brown trout, but they were found almost exclusively in backwaters and cutoff pools (i.e., off-channel habitats) in streams where brown trout were abundant. Off-channel habitat appears to provide a refuge for native fishes in streams with abundant brown trout populations. Altered or degraded streams may not include sufficient off-channel refuge habitats to allow coexistence of native species and introduced brown trout.     

Spawning ecology of finespotted Snake River cutthroat trout in spring streams of the Salt River valley, Wyoming

We studied spawning ecology of cutthroat trout ( Oncorhynchus clarki ) in streams that originate as springs along the Salt River, a Snake River tributary in western Wyoming. We assessed (1) relative numbers of upstream-migrant and resident adults present during the spawning period in spring streams, (2) influence of habitat modification on use of spring streams for spawning, and (3) habitat features used for spawning in spring streams. Four spring streams were studied, 2 with substantial modification to enhance trout habitat and 2 with little or no modification. Modifications consisted primarily of constructing alternating pools and gravel-cobble riffles. Only a small portion of adult fish in spring streams during the spawning period had migrated upstream from the Salt River between March and the middle of June. Larger numbers of adult fish and more redds were observed in the 2 modified streams compared with the 2 streams with little or no modification. Most spawning occurred on constructed riffles with small gravel and over a narrow range of depths and velocities. Cutthroat trout, rainbow trout ( Oncorhynchus mykiss ), and their hybrids were observed in 1 stream with habitat modifications, indicating that measures to halt invasion by rainbow trout, as well as habitat improvement, are needed to preserve this native trout within the Salt River valley.