Distribution and abundance of pelagic fish in Lake Powell, Utah, and Lake Mead, Arizona-Nevada

Pelagic fish communities (waters with depths > 20 m) of Lakes Powell and Mead were examined quarterly from 1995 to1998 using vertical gill nets and a scientific echosounder. Nets captured a total of 449 fish consisting of striped bass (57%/45% [Lake Powell/Lake Mead]), threadfin shad (24%/50%), common carp (15%/4%), walleye (3%), channel catfish (2%), and rainbow trout ( -1 ). Reservoirs experienced dramatic seasonal and annual fluctuations in pelagic biomass. Lake Powell's biomass peaked at the Colorado River at 709.7 (± 46.5) kg · ha -1 and Lake Mead's reached 291.9 (± 58.2) kg · ha -1 at Las Vegas Wash. These locations supported estimated fish densities of 124,668 fish · ha -1 and 15,131 fish · ha -1 , respectively. Maximum reservoir biomass peaked in August 1996, with Lake Powell supporting 10,852,738 ± 5,195,556 kg (27.6 × 10 7 fish) and Lake Mead 1,926,697 ± 892.994 kg (10.8 × 10 7 fish). Biomass ebbed in May (1996 and 1997), when Lake Mead supported 65% (296,736 kg vs. 453,097 kg) and 62% (101,016 kg vs. 162,262 kg) of biomass levels found in Lake Powell.     

Food habits of Burrowing Owls in southeastern Idaho

Food habits of a population of the Burrowing Owl ( Athene cunicularia ) at the Idaho National Engineering Laboratory, Butte County, were studied. The 421 pellets examined yielded 2,436 prey items of at least 22 prey species. Invertebrates, largely insects, constituted 91 percent of the total prey items, but only 29 percent of the total biomass; mammals constituted 8 percent of the prey items, but 68 percent of the biomass. The prey were mostly nocturnal species; diurnal species were poorly represented.     

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.         

Food habits and nest characteristics of breeding raptors in southwestern Wyoming

Food habits and nest site features of the Golden Eagle ( Aquila chrysaetos ), Prairie Falcon ( Falco mexicanus ), Red-tailed Hawk ( Buteo jamaicensis ), and Ferruginous Hawk ( B. regalis ) were studied near Medicine Bow, Wyoming, during 1981 and 1982. Foods consisted primarily of leporids and sciurids. The Wyoming ground squirrel ( Spemiophilus richardsonii ) dominated the diet of Prairie Falcons, while Golden Eagles preyed on leporids more than did the other raptors. Diet overlap ranged from 59 to 99% between the species. Mean height of Golden Eagle nests was greater than nest height of other species. Most raptor nests (78%) were not visible from other active nests and were in view of roads. Prairie Falcons were the most specialized and Ferruginous Hawks the most versatile raptor species in terms of food habits and use of nest sites.     

Food of larval tui chubs, Gila bicolor, in Pyramid Lake, Nevada

Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 st1\:*{behavior:url(#ieooui) } /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} Four near-surface locations in Pyramid Lake, Nevada, were sampled for larval tui chubs ( Gila bicolor ) during summer and early fall 1979. Numbers of larvae collected were highest in mid-July. Zooplankton was the only food eaten throughout the survey; the cladoceran Moina hutchinsoni was the major species eaten at all locations. Another cladoceran, Diaphanosoma leuchtenbergianum, was also important to the diet of pelagic larvae, and the copepod Cyclops vernalis was eaten in significant quantities by nearshore fish. Changes in diet composition of larval tui chubs during summer corresponded to seasonal succession of zooplankton species in Pyramid Lake.     

Food habits and dietary overlap of nongame insectivorous fishes in Flint Creek, Oklahoma, a western Ozark foothills stream

Insectivorous fishes were sampled from March, 1983 to February 1984, in Flint Creek, Delaware Co., Oklahoma. There was insignificant habitat segregation between Etheostoma spectabile and E. punctulatum and seasonal habitat partitioning between Cottus carolinae and both darters. Mature E. spectabile ate primarily chironomids and mayflies, whereas juveniles fed primarily on microcrustaceans. Mature E. punctulatum consumed fewer Ephemerella and Leptophlebia than E. spectabile , feeding on Stenonema and other crustaceans. Juvenile E. punctulatum fed mainly on amphipods and mayflies, and juvenile E. spectabile ate primarily microcrustaceans. Cottus carolinae elected primarily mayflies in spring - summer and chironomids in January - February. Coefficients of dietary overlap were highest between larger E. spectabile and juvenile E. punctulatum and lowest between immature E. spectabile and mature E. punctulatum . Overlap between the two darters was significantly correlated with differences in mean prey size (p E. spectabile was also significantly correlated to differences in mean prey sizes. Etheostoma spectabile generally preferred smaller prey than E. punctulatum . All three species avoided Stenelmis . Cottus carolinae avoided microcrustaceans. The study showed that resource partitioning among these three insectivorous fishes is affected by complex interactions of habitat and prey electivity, and prey size selectivity.         

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.     

Littoral heterogeneity and diel behavior of white bass ( Morone chrysops ) and carp ( Cyprinus carpio ) in Utah Lake, Utah

Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 st1\:*{behavior:url(#ieooui) } /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} Diel activity and association patterns of white bass ( Morone chrysops ) and carp ( Cyprinus carpio ) in Utah Lake, Utah, were studied over four 24-hr periods during August 1980. Fish were concurrently sampled from two adjacent littoral habitats. Significant differences existed in diel activity patterns in two of three size classes of white bass and in diel association patterns of white bass and carp between the two habitat areas. Differences in habitat structure, and in biological activity between the habitat types, are implicated as the primary determinants of overall diel activity of fish in these littoral areas.        

Late Pleistocene-early Holocene history of coniferous woodlands in the Lucerne Valley region, Mohave Desert, California

The composition of four radiocarbon-dated, late Pleistocene woodrat middens is reported and analyzed. A date of 11,850 ±550 BP records the first reported macrofossil occurrence in this region of late Pleistocene Pinus monophylla-Juniperus osteosperma woodlands. A 7,800 ±350 BP date documents the most recent J. osteosperma woodlands in this presently coniferless desert area, while a date of 12,100 ±400 BP is the oldest record of juniper woodlands among the four middens. Other juniper and creosote bush desert flora radiocarbon dates along with six pollen profiles were obtained. The research suggests that as recently as 7,800 BP this part of the Mohave Desert was subject to a cooler, moister climate than at present, and that the aboriginal food resources of pinyon seeds and juniper berries were probably available to early prehistoric man in this area.     

Food habits of the western whiptail lizard ( Cnemidophorus tigris ) in southeastern New Mexico

This study presents the first food habit assessment for the western whiptail lizard ( Cnemidophorus tigris ) in the shinnery oak – mesquite habitat ( Quercus havardii – Prosopis glandulosa ) of southeastern New Mexico. Short-horned grasshoppers, termites, antlions, beetles, and spiders formed the major portion of the diet during the four-year study. Discriminant analyses were used to evaluate annual, seasonal (monthly), and sexual variation. Incidental food categories were responsible for most of the annual and seasonal variation. Dominant foods varied little between months and years. Sexual variation was more evident; it may act to reduce intraspecific competition for food resources and may be associated with secondary sexual size dimorphism.         

Effects of land clearing on bordering winter annual populations in the Mohave Desert

Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 st1\:*{behavior:url(#ieooui) } /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} Construction of a 10-MWe solar thermal power plant in Daggett, California, involved clearing and leveling 53 ha of desert land. Transient offsite effects of this construction were apparent as a reduced density of annual plants within 100 m downwind of the edge of the cleared area. Schismus arabicus populations recovered within four years, but Erodium cicutarium populations did not. The effects appeared to be related more to an interaction of seed-dispersal mechanisms with the large, open space than to the obvious sand movement and deposition associated with the clearing operations.     

Food habits of clouded salamanders ( Aneides ferreus ) in Curry County, Oregon (Amphibia: Caudata: Plethodontidae)

Stomach contents of 650 clouded salamanders ( Aneides ferreus ), collected monthly throughout the year from Curry County, Oregon, were examined. Samples from three age classes were involved: (1) 489 adults, (2) 131 juveniles, and (3) 30 hatchlings. Foods did not vary by sex, but did vary by age and by season. Hatchlings ate small items, particularly mites, springtails, flies, and small beetles. Juveniles fed mainly on flies, isopods (sowbugs), beetles, mites, and centipedes in winter; beetles, ants, and isopods in spring; ants and beetles in summer; and isopods, beetles, and ants in fall. Adults ate isopods and beetles as their major foods in winter, spring, and fall and isopods, ants, beetles, and earwigs in summer. Four species were exceedingly important as foods for these salamanders: an unidentified isopod, the snout beetle ( Trachyphloeus bifoveatus ), the European earwig ( Forficula auricularia ), and an ant ( Lasius alienus ).       

Food habits of the threatened bat Leptonycteris nivalis (Chiroptera: Phyllostomidae) in a mating roost in Mexico

The objective of this study was to collect and present data on the food plants that a vulnerable migratory nectarivorous bat, Leptonycteris nivalis, used during its seasonal stay at a cave in Tepoztlan, Mexico. This cave is the only mating roost known for this species. Pollen grains from faeces and fur were examined. Little is known about the diet of this bat, especially in the southern half of its distribution. Pollen belonging to 10 plant species was found from five families: Cactaceae (Stenocereus beneckei), Bombacaceae (Ceiba aesculifolia, Pseudobombax ellipticum), Convolvulaceae (Ipomoea arborescens), Fabaceae (Calliandra houstoniana, Bauhinia ungulata), and Amaryllidaceae (Agave dasylirioides, A. horrida, A. inaequidens, A. salmiana). Bats showed the highest dietary diversity in November. There were no significant differences in diet between sexes. Of the four Agave species, two have paniculate inflorescences that are commonly attributed to bat pollination, while the other two had spicate inflorescences, which are considered to be primarily insect‐pollinated.     

Associations of Small Mammals Occurring in a Pluvial Lake Basin, Ruby Lake, Nevada

Ruby Lake is a highly mesic and vegetationally diverse pluvial lake basin of east central Nevada. Small mammal associations were examined in six plant communities at Ruby Lake using transects of live traps. Small mammal activity was recorded for these six habitats plus an additional three other specialized habitats. A total of 11 species of small mammals were trapped from the six habitat types; from the entire study area 26 species were trapped or observed. Two greasewood shrub habitats and a shadscale-spiny hopsage habitat held the highest number of trapped species, 6, 5, and 7, respectively. The mesic haymeadow and spring habitats, as well as the big sagebrush-antelope bitterbrush habitat held 4 trapped species each. Peromyscus maniculatus and Perognathus parvus made up 76% of the total captures and were found in all habitat types except marshlands. Eutamius minimus was found in four of the six habitat types, while Dipodomys ordii , Dipodomys microps , Perognathus parvus , and Microtus montanus were limited to specialized habitats. Mesic adapted, wetland species such as Mustela vison , Ondatra zibethicus , and Sorex vagrans possibly dispersed into Ruby Valley from the northeastern drainages and valleys during the late Pleistocene or Holocene.     

Growth of smallmouth bass ( Micropterus dolomieu ) in Flaming Gorge Reservoir, Wyoming-Utah

Growth of smallmouth bass ( Micropterus dolomieu ) was described for three widely spaced areas progressing downstream in Flaming Gorge Reservoir, Wyoming-Utah. Significant differences among areas were detected only for age-1 fish. Growth in the reservoir was compared with that of populations in other lentic habitats of varying growing season lengths in North America; slow growth in the reservoir was related to the relatively short growing season (less than 90 days).     

Productivity, food habits, and associated variables of Barn Owls utilizing nest boxes in north central Utah

Productivity and food habits of the Barn Owl ( Tyto alba ) utilizing nest boxes in Juab, Utah, and Salt Lake counties, Utah, During 1979-1984 were examined. Average clutch size was 5.8 eggs for the 6-yr period; mean number fledged was 3.9 young per successful nest. While severe weather during the 1981-82 winter did not result in significant decrease in productivity during the 1982 breeding season, it may have resulted in a significant overproduction of female young. Barn Owls in north central Utah fed almost exclusively on mammalian species, particularly Microtus spp. Difference in clutch size between areas and years may be a response to availability as well as abundance of prey.     

Autumn and winter food habits of bobcats in Washington state

The stomach contents were examined from 324 western Washington bobcats ( Felis rufus ) and 123 from eastern Washington taken by hunters from 1976 through 1980, for major prey items as well as sex- and age-related differences in diet. Western Washington bobcats ate primarily mountain beavers ( Aplodontia rufa ) (42% occurrence) and snowshoe hares ( Lepus americanus ) (26%). Within that population females ate larger quantities of smaller prey such as douglas squirrels ( Tamiasciurus douglasi ) and lesser amounts of deer ( Odocoileus sp.) than males. Bobcat diets in eastern Washington were more diverse; main foods consisted of lagomorphs ( Sylvilagus nuttallii, Lepus sp.) (20%), red squirrels ( Tamiasciurus hudsonicus ) (15%), deer (11%), and voles ( Microtus sp.) (11%). Age-related differences were most prevalent in this population, with adults consuming larger quantities of deer and larger prey than did kittens.     

Prey selection and food habits of Burrowing Owls in Colorado

Food habits of Burrowing Owls ( Speotyto cunicularia ) were studied during the breeding seasons of 1990 and 1991 in central Colorado. Concurrent insect availability studies were conducted to determine selection for specific insect families. Analysis of 1445 castings indicated use of only one insect family, the carrion beetles (Silphidae), at a rate greater than expected based on availability in one year. Castings and prey remains showed different dietary components. Prey remains showed greater use of small mammals, moths, amphibians, and passerines, and castings indicated greater use of mice and beetles. Methodology in raptor food habits studies may therefore bias results.     

Timing, distribution, and abundance of kokanees spawning in a Lake Tahoe tributary

We counted kokanee spawners and carcasses every 1-7 days from mid-September through mid-November in 1991 and 1992 in Taylor Creek, a tributary to Lake Tahoe, California-Nevada. Less than 1% of the spawning run entered Taylor Creek before flow from Fallen Leaf Lake was increased on 2 October 1991; in 1992 the peak occurred on 30 September or 1 October after flows increased on 29 September. In both years spawners concentrated in the middle three of five stream reaches below the impassable Fallen Leaf Lake dam. From tab-and-recovery experiments, the average longevity of male spawners in the stream was 3.5 days in 1991 and 2.8 days in 1992, whereas the average female longevity was 2.0 days in 1991 and 2.3 days in 1992. Observed carcasses accounted for less than 10% of spawners counted, suggesting removal by scavengers or high predation on prespawners. An estimated 1928 males and 1309 females spawned in 1991, and 8021 males and 8712 females spawned in 1992. Our estimate of 3237 spawners in 1991 compared favorably to our estimate of 3520 ± 1474 prespawners staging in Lake Tahoe in mid-September. An index of kokanee abundance in Lake Tahoe has historically been based on 1-day surveys every 1 November since 1960; however, estimated total spawner abundance was 19 times higher than the annual index of 158 spawners in 1991, 141 times higher than the index count of 100 spawners in 1992. The index count and mean fork lengths of spawners (278 ± 10 mm [2 SE] for males, and 248 ± 3 mm for females) in 1991 and 1992 were the lowest on record.