Life history, abundance, and distribution of Moapa dace ( Moapa coriacea )

Moapa dace ( Moapa coriacea ) is a federally listed endangered fish endemic to the spring-fed headwaters of the Muddy River, Clark County, Nevada. Species life history, abundance, and distribution were studied from March 1984 to January 1989. Reproduction, which was observed year-round, peaked in spring and was lowest in fall. It occurred in headwater tributaries of the Muddy River within 150 m of warm water spring discharge in water temperatures ranging from 30 to 32 C. Females matured between 41 and 45 mm in fork length (FL). Egg abundance increased with female size ( r 2 = .93); counts ranged from 60 for a 45-mm-FL female to 772 for one 90-mm FL. The oldest of eight fish, aged by the opercle method, was a 90-mm-FL, 4+-year-old female. Adults are omnivorous but tended toward carnivory; 75% of matter by volume consumed was invertebrates and 25% plants and detritus. Fish size was generally commensurate with flow, the largest fish occurring in the greatest flow. Adults were near bottom, in focal velocities ranging from 0 to 55 cm/s. Juveniles occupied a narrower range of depths and velocities than adults, and larvae occupied slack water. From December 1984 to September 1987, the total adult population ranged from 2600 to 2800. Although these numbers are higher than previously believed for Moapa dace, they are still sufficiently low to warrant its endangered status. The dependency of Moapa dace's different life history stages to various areas and habitat types of the Warm Springs area suggests that all remaining habitat is necessary for their survival.     

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.     

Conservation status of threatened fishes in Warner Basin, Oregon

Two federally listed fishes, the Foskett speckled dace and Warner sucker, are endemic to Warner Basin in south central Oregon. The Foskett speckled dace is native only to a single spring in Coleman Valley. A nearby spring was stocked with dace in 1979 and 1980, and now provides a second population. The present numbers of dace probably are at their highest levels since settlement of the region. The Warner sucker historically occurred throughout much of the Warner Valley, but its distribution and abundance have been reduced by construction of reservoirs and irrigation dams and the introduction of predatory game fishes. Lentic habitats have become dominated by introduced fishes, particularly white crappie, black crappie, and brown bullhead. The largest remaining population of Warner suckers occurs in Hart Lake, where successful reproduction was documented but there is no evidence of recruitment to the adult population.     

A fish survey of the White River, Nevada

In spring and summer 1991 and 1992, we surveyed fishes of the White River system, Nye and White Pine Counties, Nevada, to determine the status of natives. There are 5 known native fishes to the White River: Lepidomeda albivallis (White River spinedace), Crenichthys baileyi albivallis (Preston White River springfish), Crenichthys baileyi thermophilus (Moorman White River springfish), Catostomus clarki intermedius (White River desert sucker), and Rhinichthys osculus ssp. (White River speckled dace). All 5 had declined in range. Lepidomeda albivallis had experienced the greatest decline, with less than 50 remaining, and these were restricted to a 70-m stream reach. Rhinichthys osculus spp. was most widespread, found in 18 spring systems. Cottus bairdi (mottled sculpin) was collected for the 1st time from the White River system, where it was probably native. Protective measures should be implemented to conserve all native White River fishes to include C. bairdi.     

Arbuscular mycorrhizae in thermal-influenced soils in Yellowstone National Park

Mycorrhizae are common plant-fungal symbioses occurring in most land plants. Despite their ubiquity, little is known about the distribution of arbuscular mycorrhizae (AM) in extreme environments. We surveyed for the presence of AM in thermal sites in Yellowstone National Park (YNP) where soils are characterized by extreme pHs, elevated temperatures, and toxic element concentrations. Plants at 5 sites, growing in soils with rooting-zone temperatures up to 48°C and soil pH values as low as 3.4, were mycorrhizal (colonization levels from 4% to 34%). Soils from a sparsely vegetated thermal area and an adjacent, continuously vegetated transition area differed significantly in rooting-zone temperature (35°C vs. 26°C), acidity (pH 3.8 vs. 5.4), electrical conductivity (2.22 vs. 0.49 mmhos cm -1 ), Fe (181.3 vs. 48.5 mg kg -1 ),Mn (7.2 vs. 98.2 mg kg -1 ), and Zn (2.3 vs. 4.5 mg kg -1 ). Mycorrhizal infectivity potential (MIP) was 77% greater in the transition soils, with colonization levels of 26% and 46% in thermal and transition soils, respectively. Furthermore, colonization of Agrostis scabra , Dichanthelium lanuginosum , and Mimulus guttatus was found to be consistently high throughout the growing season (from 48% to 72%). It is possible that AM are essential for plant life on the edge of thermal areas, and that either or both symbionts are specifically adapted to their environment. Further research is required to elucidate AM function in and specific adaptations to YNP's thermal areas.     

Distribution, movements, and habitat use of razorback sucker ( Xyrauchen texanus ) in a lower Colorado River reservoir, Arizona-Nevada

Distribution, movements, and habitat use of 10 wild adult razorback suckers ( Xyrauchen texanus ) were examined in Lake Mohave, Arizona-Nevada, from November 1994 through July 1997. Movement rates (0.00-17.35 km d -1 ) and ranges ( x = 39 km) were similar to those for riverine populations. All study fish returned to spawning sites used in previous years, but they also visited other spawning areas. Spawning females were significantly ( P = 0.031) more active than males (480 vs. 87 m d -1 ) and moved substantial distances between spawning sites during peak reproduction (1-28 February). Fish became most active (m d -1 , km month -1 ) after spawning and moved to areas known to support higher algal production. Fish were typically within 50 m ( P 30.0 m). Adults were detected throughout the available thermal gradient (12°-30°C), but during summer typically had body temperatures between 18° and 22°C. Vertical movements within the water column showed no correlation with depth or time of day, but seasonal shifts suggest fish may regulate body temperature by seeking specific temperatures during reservoir stratification.     

Seasonal habitat use and selection of Chukars in west central Idaho

We examined radio-marked Chukar ( Alectoris chukar ) habitat use and selection in west central Idaho during spring and summer of 1995 and 1996. Use of habitats also was compared with abundance and distribution of yellow starthistle ( Centaurea solstitialis ), an exotic species that is increasingly abundant in Chukar habitats. During summer Chukars used areas of southeast aspect 12% less ( P = 0.002) and areas of northwest aspect 11% more ( P = 0.008) than in spring. Chukars also used areas that averaged 9% steeper slopes ( P P = 0.054) in summer than in spring. Shrub cover types were used 22% more ( P P P P P < 0.05) than expected, implicating the detrimental effects of this exotic plant on habitat use of Chukars.     

Zonation patterns in the vascular plant communities of Benton Hot Springs, Mono County, California

Vascular plant communities surrounding Benton Hot Springs, Mono County, California, were studied. The springs complex is comprised of two thermal springs, a thermal stream, and a cooling pond. Water temperatures varied from 57 C in one hot spring to 45 C at the cooling pond. The vegetation showed concentric zones about the springs and cooling pond and parallel zones beside the stream. Each zone demonstrated its own dominant plant species with some species being present in two or more zones. A total of six zones were identified plus an algal mat on the springs themselves. Soil factor patterns varied from spring to desert as did vegetational parameters. Soil moisture appeared responsible for most of the patterns observed.     

Occurrence and habitat use of passage neotropical migrants in the Sonoran Desert

Little is known about stopover habitat use by neotropical migratory birds in the deserts of North America. We determined distribution, abundance, and habitat associations of neotropical migrants during spring migration in the Sonoran Desert of southwestern Arizona along large washes that supported xeroriparian scrub vegetation. We detected 91 bird species during surveys, 50 (52%) of which were passage neotropical migrants. Although xeroriparian scrub covered less than 55% of the area surveyed, 97% of all detections of passage migrants were from this vegetation type. By calculating habitat breadth for each species, we classified 87% of passage migrants as xeroriparian specialists. Richness of passage migrants was strongly associated with the presence of overstory (> 2.5 m) mesquite and paloverde. The highest species richness of breeding neotropical migrants was associated with width of the xeroriparian corridor. Habitat characteristics we have shown to be important to neotropical migrants can be preserved and managed by protecting xeroriparian areas, particularly those supporting mature (> 2.5 m) paloverde, mesquite, desert willow, and catclaw acacia trees. Additionally, xeroriparian scrub within the creosote-bursage vegetation type may be particularly important to passage neotropical migrants.     

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.     

Variation in the life history and abundance of three popluations of Bruneau hot springsnails ( Pyrgulopsis bruneauensis )

Bruneau hot springsnail density, size class structure, recruitment, and mortality were measured monthly over approximately 2 years and compared to environmental variables at 3 hot spring sites in southwestern Idaho. Food resources (attached algae) and water chemistry were similar among sites, but temperature, population density, and size structure differed significantly. Density was highest at a warm, fairly constant temperature site. A cooler, highly variable temperature site and a site where temperatures frequently approached or exceeded thermal maxima tolerance limits had lower densities. Size class structure varied seasonally and distinctly among sites, with recruitment occurring year-round at temperatures < 36°C. Mortality affected different size classes at different sites, with smaller snails incurring greatest mortality at site 3 (highest temperature variability). Growth rates were positively correlated with temperatures up to 36° C. Mean snail size differed among sites and also appeared to be related to temperature, with the variable temperature sites having larger snails. Although these snail populations are found in a range of water temperatures, they appear best adapted to springs with mean temperatures between 32° and 33°C and low thermal variance.     

Current studies on the rare Chinese black muntjac

Summary

For several decades there have been no reports on the black muntjac (Muntiacus crinifrons), and it has been listed as an endangered species. During the past few years we have discovered there are black muntjac in 37 countries of four provinces in east China. The geographical distribution is very narrow, and limited to the eastern part of China which lies between 28°–31°N. lat. and 117°–120°E. long. This paper describes the results of our study of the black muntjac. Details are given of the habitat and distributions of the 43 adult specimens captured and studied recently.     

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.     

Burrow occupancy patterns of the Western Burrowing Owl in southern Nevada

Understanding long-term patterns of burrow occupancy for the Western Burrowing Owl ( Athene cunicularia hypugaea ) is necessary for the conservation of this species, especially in arid, desert ecosystems where burrow occupancy data are lacking. Monthly burrow monitoring was conducted over a 4-year period (1997&ndash;2001) in southern Nevada to determine burrow occupancy patterns of Burrowing Owls and to evaluate the effects of burrow type and desert region on burrow occupancy. Burrow occupancy occurred year-round and was most consistent in the Transition region and tended to be lowest in the Mojave Desert region. Peak burrow occupancy occurred during March through May, followed by a gradual decline in occupancy through the summer and fall until January and February, when occupancy was lowest. Occupancy was significantly higher at sites with both culvert and pipe burrows than at sites with earthen burrows in disturbed habitat or earthen burrows in natural habitat. Breeding-season occupancy was not significantly higher in wetter, cooler portions (e.g., Great Basin desert region) of the study area. Results suggest that occupancy is influenced by habitat features&mdash;such as suitable burrows in open areas with low vegetation&mdash;and climatic regime.     

Post-breeding season movements of Columbia spotted frogs ( Rana luteiventris ) in northeastern Oregon

Movements of Columbia spotted frogs ( Rana luteiventris ) were determined after breeding to provide managers with information on habitat requirements. We radio-tagged 47 adults and observed movements occurring with 22 frogs. Eleven frogs remained in breeding ponds, and 11 moved to other ponds or river stretches during spring and summer 1998. Distances frogs traveled to other water bodies ranged from 15 to 560 m. Movements appeared to be influenced by availability of habitat and aquatic conditions. Eleven of 16 frogs located within 100 m of other permanent water sources moved, while no frogs at an isolated breeding pond moved. Frogs moved to river stretches in July where water temperatures averaged 5.6 ° C cooler than ponds. Knowledge of Columbia spotted frog movements and habitat use in summer enables land managers to make decisions on activities that affect aquatic sites, vegetation, and stream structures that may influence frog populations.     

Stream temperatures and the elevational distribution of redband trout in southwestern Idaho

During July to September 1994-1995, I examined water temperatures at the lower end of the elevational distribution of redband trout ( Oncorhynchus mykiss gairdneri ) in 4 streams in the Owyhee Mountains in southwestern Idaho. Maximum water temperatures in Castle, Shoofly, Little Jacks, and Big Jacks creeks during low flows during a drought in 1994 ranged from 26.7° C to 29.0° C. Water temperatures fluctuated 9.5-11° C during the 24-h period maximum temperatures were observed. Stream flows at the lower end of Big Jacks and Little Jacks creeks in 1994 were 3 s -1 and subsided underground 50-130 m downstream pools inhabited by trout. Trout were distributed to lower elevations where drainage basin area was larger in 2 of 3 yr ( P 5 km downstream of the lowest pool inhabited by trout in 1995-1996.     

Changes in the distribution and status of sage-grouse in Utah

Sage-grouse ( Centrocercus spp.) were abundant in all of Utah's 29 counties at the time of European settlement wherever sagebrush ( Artemisia spp.) occurred. Greater Sage-Grouse ( C. urophasianus ) inhabited areas north and west of the Colorado River, and Gunnison Sage-Grouse ( C. minimus ) occupied suitable habitat south and east of the Colorado River. The largest Greater Sage-Grouse populations in Utah are currently restricted to suitable habitats in Box Elder, Garfield, Rich, Uintah, and Wayne Counties. A remnant breeding population of Gunnison Sage-Grouse occurs in eastern San Juan County. We stratified Greater Sage-Grouse populations (1971-2000) by counties where the 1996 to 2000 moving average for estimated spring breeding populations was > 500 (GT500) or < 500 (LT500). Males per lek declined in all populations from 1971 to 2000; however, there were consistently more males observed on GT500 than on LT500 leks. Juveniles per adult hen (including yearling hens) Greater Sage-Grouse in the 1973-2000 fall harvest in Box Elder, Rich, and Wayne Counties did not differ from 2.25, a ratio suggesting sustainable or increasing sage-grouse populations. Declines are attributed to loss, fragmentation, and degradation of sagebrush habitat. Sage-grouse conservation ultimately depends on management and enhancement of remaining sagebrush rangelands in Utah.     

Observations on the reproduction, sources of mortality, and diet of the Kendall Warm Spring dace

The life history of the endangered Kendall Warm Springs dace ( Rhinichthys osculus thermalis ) is largely unknown. Our study of its reproduction, sources of mortality, and diet indicated that Kendall Warm Springs dace seem to be reproductively active throughout the year, but the rate of reproduction appears to decrease during the winter. Males become sexually mature at 34 mm total length and females at 40 mm total length. We observed 2 sources of mortality: (1) emigration from the warm spring over a waterfall into the Green River and (2) predation on larvae by dragonfly ( Libellula saturata ) nymphs. Stomachs of Kendall Warm Springs dace contained small (≤ 1.5 mm total length) benthic invertebrates, primarily dipterans and mollusks.     

Oribatid mite (Acari) community structure in steppic habitats of Burgos Province,central northern Spain

This work is a study of the communities of oribatid mites in steppic areas of Burgos Province, central northern Spain, in relation to different habitat types belonging to natural or disturbed ecosystems. The primary objective was to find the relationship between anthropogenic use of land and several diversity indices. Parameters such as abundance, species richness, real diversity (H′) and equitability (J′) of the mite communities were calculated in 20 soil plots, sampled in spring and autumn 2000, belonging to the predominant habitat types of this area: (1) cultivated lands, (2) abandoned crop lands, (3) grasslands/pastures, and (4) natural oak forests or a pine plantation. The most widespread species in the area as well as the most abundant taxa overall are documented, together with the faunistic checklist of oribatid mites identified in the study. The results show a general decline in the composition of the oribatid community, in terms of species diversity and abundance, from non‐disturbed soils to cultivated lands. The number of species (richness) was usually higher in forest soils than in disturbed ecosystems, in which the most degraded soils showed the lowest number of species. The community analysis shows the differences due to habitat type and ubiquitous bioindicator species.     

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.