Occurrence of native Colorado River cutthroat trout ( Oncorhynchus clarki pleuriticus ) in the Escalante River drainage, Utah

Field surveys were conducted during 1997 and 1998 documenting the distribution and abundance of Colorado River cutthroat trout ( Oncorhynchus clarki pleuriticus ) in Escalante River tributaries. This documented occurrence of native trout in the Escalante River drainage of southern Utah represents an expansion of the known historic range of this subspecies as reported before the 1990s. We found 5 populations of native trout ranging in biomass from 3.0 to 104.2 kg ha -1 and occupying 13.2 km of stream of 130 km of estimated historic habitat. Current distribution and abundance of Colorado River cutthroat trout were compared to early introductions of nonnative trout stocked for sport fishing purposes. Native cutthroat trout have been displaced by nonnative cutthroat trout ( O. c. bouveri ), rainbow trout ( O. mykiss ), brook trout ( Salvelinus fontinalis ), and brown trout ( Salmo trutta ) except where they were isolated by physical or biological barriers. Displacement may have been more extensive except for the remoteness of the drainage and relatively recent introductions of nonnative trout. These conditions limited the overall amount of the drainage stocked, numbers of nonnative trout stocked, and time over which stocking occurred. Discoveries of native trout populations within the Escalante River drainage have allowed expanded conservation of this subspecies by adding new populations to what was known to exist and by increasing the known natural range of this fish.     

Effects of elevation and genetic introgression on growth of Colorado River cutthroat trout

Inland populations of cutthroat trout have suffered dramatic declines and some subspecies are considered threatened or endangered. Understanding patterns of variation and factors that influence life history in populations is important for conservation and management. We determined effects of elevation, sex, and genetic introgression (with Yellowstone cutthroat trout, Oncorhynchus clarkii lewisi , and rainbow trout, Oncorhynchus mykiss ) on growth rates of Colorado River cutthroat trout ( Oncorhynchus clarkii pleuriticus ) in the Sheep Creek drainage in the Uinta Mountains of Utah. In this high-elevation system, native trout grew slowly and matured relatively late. Elevation, sex, and genetic introgression all had significant effects on growth rates. Growth rates were lower at higher elevations. Males were slightly larger than females, and cutthroat trout in locations that were more introgressed grew faster than those at nonintrogressed locations. Both abiotic effects and effects of introduced salmonids must be addressed in long-term management programs to ensure the sustainability of native trout populations.     

Current status of cutthroat trout subspecies in the western Bonneville Basin

Recent discoveries of native cutthroat trout populations in desert mountain ranges on the western fringe of the Bonneville Basin have prompted intensified management efforts by state and federal agencies. Analysis of Snake Valley cutthroat specimens in Trout Creek, Deep Creek Mountain Range, Utah, indicate this is a pure strain of the trout which once inhabited Pleistocene Lake Bonneville and which was thought to be extinct in Utah. The Snake Valley cutthroat is similar to Salmo clarki utah of the eastern Bonneville Basin; however, electrophoretic and morphomeristic analysis show unique genetic differences brought about by long - term isolation (8,000 years) from the remainder of the Bonneville Basin cutthroat. This cutthroat is a common ancestor to several other limited cutthroat populations within the basin in Nevada. In May 1977 the BLM withdrew from mineral entry about 27,000 acres within the Deep Creek Mountains for protection of this salmonid cutthroat and other unique resources on the range. Results of 1977 stream surveys on the Pilot Peak Mountain Range, Utah, indicate the presence of the threatened Lahontan cutthroat, Salmo clarki henshawi, in one isolated stream.     

Distribution and abundance of native Bonneville cutthroat trout ( Oncorhynchus clarki utah ) in southwestern Utah

The Bonneville cutthroat trout ( Oncorhynchus clarki utah ; BCT) was once abundant throughout the Bonneville Basin. In southwestern Utah, however, only 3 local populations of the subspecies were known to exist in 1977, when conservation efforts to protect and replicate them began. By 1995 remnant populations were known in 6 streams, and replicate populations had been established in an additional 16. Populations of BCT in southwestern Utah streams were survey by electrofishing in 1994 and 1995 to describe the subspecies' status. Estimated densities of age-1 and older BCT ranged from 118 to 546 fish per km. Biomass estimates ranged from 8 to 64 kg per ha. Several age groups of BCT were collected at most locations. Six populations were classified as self-sustaining, 9 as expanding through natural recruitment, 6 as new, and 1 as hybridized. Overall status of BCT in southwestern Utah has improved since 1977, but conservation measures must continue to maintain a positive trend.     

Diets of sympatric Lahontan cutthroat trout and nonnative brook trout: implications for species interactions

Nonnative brook trout ( Salvelinus fontinalis ) have been implicated in declines of stream-living Lahontan cutthroat trout ( Oncorhynchus clarki henshawi ), a threatened trout endemic to the Lahontan Basin of northeastern California, southeastern Oregon, and northern Nevada. Brook trout may displace Lahontan cutthroat trout through 2 mechanisms: interspecific predation and competition for food. To evaluate the evidence for these alternatives, we examined stomach contents of 30 trout of each species captured in the North Fork Humboldt River, northeastern Nevada, to compare number, size, and taxonomic composition of prey. Taxonomic dietary overlap was high (81.4%) between brook and Lahontan cutthroat trout. Both species were nonselective in their feeding habits. Lahontan cutthroat trout consumed over 2.5 times as many prey on average, but brook trout consumed significantly larger prey. No trout of either species occurred in fish diets. Only a single fish, a Paiute sculpin ( Cottus beldingi ), was found in stomachs, and the majority (>90%) of prey consisted of insect taxa. Size and number of prey consumed were positively related to fish size for Lahontan cutthroat trout, but not for brook trout. These results do not provide compelling evidence to suggest feeding by Lahontan cutthroat trout is limited by presence of large numbers of brook trout in the North Fork Humboldt River. However, fundamental differences in each species utilization of food in this system indicate that a better understanding of observed differences may help to explain the variable success of brook trout invasions across stream habitats in the Lahontan Basin and their potential effects on Lahontan cutthroat trout.     

Comparative tolerance of four stocks of cuttthroat trout to extremes in temperature, salinity, and hypoxia

Four stocks of cutthroat trout ( Oncorhynchus clarki ) were exposed to high temperature, high salinity, and low dissolved oxygen to determine inherent differences. The fish tested included 2 stocks of Bonneville cutthroat trout ( O. c. utah ), a lacustrine stock derived from Bear Lake and a fluvial-origin stock from southern Utah (Manning Meadow Reservoir). The other 2 stocks tested were from Electric Lake (largely Yellowstone cutthroat trout, O. c. bouvieri ) and Jackson Hole, Wyoming (fine-spotted Snake River cutthroat trout, O. c. subsp.). Temperature tests were either critical thermal maximum (CTM) or 96-hour trials using juveniles acclimated between 12.5° C and 18.0° C. Two CTM end points were temperature at first loss of equilibrium (CTM eq ) and onset of spasms (CTM s ). There were no significant differences in CTM eq among test fish acclimated to 18.0° C, but CTM s was significantly higher for Bear Lake Bonneville (30.0°C) than for Snake River (29.6° C) or southern Bonneville (29.7° C) stocks. With fish acclimated at 13.0° C, there were no significant differences among the stocks in CTM eq or CTM s . Differences among stocks varied significantly among nine 96-hour tests. Overall, it appeared that the southern Bonneville stock had slightly better survival at warmer temperatures than other stocks. In 24-hour survival tests at high salinities, the Snake River stock had the lowest tolerance, with significant mortality occuring at 18% (29.5 mS · cm -1 conductivity). The southern Bonneville stock had the highest tolerance, with no mortality until 22% (38 mS · cm -1 ). Bear Lake Bonneville and Electric Lake stocks had 60% and 30% mortality, respectively, at 21% (36 mS · cm -1 ). Hypoxia tolerance measured by resistance time, 24-hour mortality, or probit analysis (LEC 50 ) did not differ among stocks. The 24-hour LEC 50 was 2.34 mg O 2 · L -1 for all stocks combined.     

Phylogenetic divergence in a desert fish: differentiation of speckled dace within the Bonneville, Lahontan, and upper Snake river basins

Historical events have had a great impact on the biogeography of fishes of western North America. We examined the genetic variation of the speckled dace ( Rhinichthys osculus ) to determine the effects on this species of extensive hydrological changes during the last 10 million years in the Bonneville and Lahontan basins of the Great Basin and the upper Snake River Basin. Eight hundred sixty-nine base pairs of the mitochondrial gene cytochrome b were sequenced from 97 individuals representing 22 populations within these 3 basins, as well as from 2 individuals of longnose dace ( Rhinichthys cataractae ) that served as outgroups. Additionally, 13 speckled dace sequences representing 3 Bonneville populations were used from GenBank. Phylogenetic relationships were reconstructed using maximum parsimony and maximum likelihood criteria. Analysis of molecular variance was used to determine population structure and to estimate the amount of gene flow across the community boundaries. Three distinct clades were reconstructed representing the Lahontan Basin, the northern Bonneville and upper Snake River basins, and the southern Bonneville Basin. Additionally, most of the population structuring was explained by variation among basins (65.33%). Speckled dace demonstrated high genetic variation. As hypothesized, the northern and southern Bonneville specimens formed separate clades; however, the southern Bonneville clade was basal to a sister clade formed by the northern Bonneville/upper Snake River and Lahontan clades. These relationships indicate that Pliocene connections between the Snake, Lahontan, and Bonneville drainages, rather than more recent Pleistocene connections, best explain population structuring in speckled dace.     

The scotopic visual sensitivity of four species of trout: a comparative study

We compared the maximum scotopic visual sensitivity of 4 species of trout from twilight (mesotopic) to fully dark-adapted vision. Scotopic vision is the minimum number of photons to which a fully dark-adapted animal will show a behavioral response. A comparison of visual sensitivity under controlled laboratory conditions showed that brown trout ( Salmo trutta ) and brook trout ( Salvelinus fontinalis ) had maximum scotopic thresholds (1.1 × 10 –4 μmol ? m –2 s –1 , ～0.005 lux) 2 times lower than rainbow trout ( Oncorhyncus mykiss ) and Snake River cutthroat trout ( Oncorhynchus clarki bouvieri ), which did not differ from each other (2.1 × 10 –4 μmol ? m –2 s –1 , ～0.01 lux). A literature review tended to corroborate these results in that brown trout and brook trout were reported to be more active during the night and at twilight than cutthroat trout and rainbow trout. We also measured light intensity within open versus shaded reaches during the day, dusk, and night in 3 Rocky Mountain streams. The scotopic sensitivity of brown trout and brook trout was sufficient to allow foraging during all twilight periods and under average nighttime light intensities in open and shaded reaches, whereas the scotopic sensitivity of rainbow trout and cutthroat trout may restrict their foraging to relatively bright nocturnal conditions (twilight or a moonlit night). Native cutthroat trout restoration efforts may have greater success in open versus shaded stream reaches in the Rocky Mountains and elsewhere.     

Host-parasite studies of Trichophrya infesting cutthroat trout ( Salmo clarki ) and longnose suckers ( Catostomus catostomus ) from Yellowstone Lake, Wyoming

Trichophrya sp. (Protozoa) on the gills of cutthroat trout ( Salmo clarki ) and longnose suckers ( Catostomus catostomus ) was studied using light and electron microscopy and tracer techniques. All cutthroat trout, 14 cm in total length and above, from Yellowstone Lake, Yellowstone National Park, Wyoming, were infested with the suctorian. No trichophryans were found on fry or fingerling cutthroat trout. Sixty percent of the examined longnose suckers from the same location were infested. Light microscopy disclosed extensive pathology of gill epithelium in longnose suckers infested with Trichophrya that was not observed for infested cutthroat trout. Electron micrographs show damage to immediate host gill cells by both parasites, depicted by a reduction and lack of mitochondria. Both parasites form attachment helices (0.52 × 0.04 μ m), which may originate in the protozoan cell membrane and function for maintenance of parasite position on the host cell. There was no uptake of 14 C, injected into host fish, via the attachment helices by the parasite that further substantiated the mechanical function for the spiral structure. Protozoan feeding on host tissue may be accomplished by use of necrotic gill tissue and mucus.        

Size selection of food by cutthroat trout, Salmo clarki, in an Idaho stream

The mean size of food and amount of food consumed by cutthroat trout from Palisades Creek in southeastern Idaho increased with trout length. Number of organisms of terrestrial origin, number of aquatic larvae, number of ants, and number of berries from redstem dogwood were related to trout length. The size range and number of taxa consumed increased with trout size, indicating that as trout get larger, they broaden their feeding menu. The minimum size of food consumed was relatively constant for all trout, but larger trout appeared to feed more from the stream bottom. Trout may have a minimum length of food, below which items cannot be detected as food. Other possible factors affecting the feeding of cutthroat trout are mentioned.         

The effects of varied densities on the growth and emigration of adult cutthroat trout and brook trout in fenced stream enclosures

We evaluated the effects of various density treatments on adult fish growth and emigration rates between Bonneville cutthroat trout Oncorhynchus clarki utah and brook trout Salvelinus fontinalis in stream enclosures in Beaver Creek, Idaho. We used 3 density treatments (low, ambient, and high fish densities) to evaluate density-related effects and to ensure a response. Intraspecific ambient-density tests using cutthroat trout only were also performed. Results indicated an absence of cage effects in the stream enclosures and no differences in fish growth between ambient-density stream-enclosure fish and free-range fish. Brook trout outgrew and moved less than cutthroat trout in the stream enclosures, especially as density increased. In all 3 density treatments, brook trout gained more weight than cutthroat trout, with brook trout gaining weight in each density treatment and cutthroat trout losing weight at the highest density. At high densities, cutthroat trout attempted to emigrate more frequently than brook trout in sympatry and allopatry. We observed a negative correlation between growth and emigration for interspecific cutthroat trout, indicating a possible competitive response due to the presence of brook trout. We observed similar responses for weight and emigration in trials of allopatric cutthroat trout, indicating strong intraspecific effects as density increased. While cutthroat trout showed a response to experimental manipulation with brook trout at different densities, there has been long-term coexistence between these species in Beaver Creek. This system presents a unique opportunity to study the mechanisms that lead cutthroat trout to coexist with rather than be replaced by nonnative brook 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.     

Sources of variation in counts of meristic features of Yellowstone cutthroat trout ( Oncorhynchus clarki bouvieri )

We determined variability in counts of meristic features (pyloric caecae, vertebrae, pelvic fin rays, gillrakers, basibranchial teeth, scales above the lateral line, and scales in the lateral series) of Yellowstone cutthroat trout ( Oncorhynchus clarki bouvieri ) by 3 independent readers, by the same reader on 3 different occasions, and among fish from 12 sampling sites within a 650-km 2 watershed. Genetic purity of the cutthroat trout was determined by electrophoretic analysis. Significant differences in meristic counts were observed among 3 readers and among sampling sites, but not among 3 occasions by a single reader. Scale counts were within the reported range for Yellowstone cutthroat trout, but counts of other structures (pyloric caecae, gillrakers, vertebrae) were as similar to rainbow trout as to Yellowstone cutthroat trout. Meristic counts identified the fish as cutthroat trout; however, variation among readers and sampling sites, as well as within the species, limits their use when identifying genetically pure cutthroat trout or assessing possible integration with rainbow trout.     

Evaluation of fish diplostomatosis in Strawberry Reservoir following rotenone application: a five-year study

Strawberry Reservoir, Wasatch County, Utah, was treated with rotenone in August 1990. For 5 yr following treatment, about 2000 fish from 5 different species were examined for eye metacercariae ( Diplostomum ). Incidence dropped from 88.0% before to 0.1% after treatment for cutthroat trout ( Oncorhynchus clarki ), from 93.0% to 0.1% for rainbow trout ( O. mykiss ), and from 19.0% to 10.0% for redside shiner ( Richardsonius balteatus ). Average numbers of metacercariae per eye also dropped from 6.8 to 0.1 for cutthroat trout, from 23.1 to 0.1 for rainbow trout, and from 18.9 to 0.1 for redside shiner. Kokanee salmon ( O.nerka ), introduced into the reservoir 1 yr after treatment, had a 0.9% prevalence rate and average of 0.1 metacercariae per eye. Rotenone affected almost all organisms in the system. Low incidence of diplostomatosis after treatment indicates that rotenone effectively destroyed many intermediate hosts (fish, snails), which in turn probably affected parasite burdens in definitive hosts (gulls). These changes in metacercariae per host probably occurred because of the complex life cycle of the organism, which is similar to the other trematodes. Rotenone is a specific inhibitor of electron transport complex I and can be devastating to parasites with complex life cycles. Through a combination of factors, parasite numbers have decreased in Strawberry Reservoir.     

Parasites of the cutthroat trout, Salmo clarki, and longnose suckers, Catostomus catostomus, from Yellowstone Lake, Wyoming

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;} Twenty-five cutthroat trout ( Salmo clarki ) and eight longnose suckers ( Catostomus catostomus ) from Yellowstone Lake, Wyoming, were collected and examined for parasites in 1985. Cutthroat trout had at least six different species of parasites that included both protozoans and helminths. The greatest number of parasite species on one fish was nine. Parasites added to the known list for cutthroat trout from Yellowstone Lake, Wyoming, were: Myxosoma sp., Diphyllobothrium ditremum, Diphyllobothrium dendriticum, Diplostomum baeri, and Posthodiplostomum minimum. These data were compared with a previous survey (1971) and a checklist of parasites of cutthroat trout in North America. There are 17 species of parasites and two fungal species reported for cutthroat trout from Yellowstone Lake. Trichophrya catostomi, Diplostomum spathaceum, and Ligula sp. were observed in the small sample of longnose suckers.        

Aquatic parameters and life history observations of the Great Basin spadefoot toad in Utah

The distribution and breeding habitats of the Great Basin spadefoot toad ( Scaphiopus intermontanus ) were investigated in the Bonneville Basin of western Utah. The permanent springs and man-made reservoirs used for breeding were largely found below the 1600 m elevation. The pH's ranged between 7.2 and 10.4 and the total dissolved solids between 170 and 4800 mg/l. The springs were less alkaline than the rain-filled reservoirs. The lack of aquatic vegetation was a common feature of the reservoirs and most of the springs. Observations of breeding without rain are noted as well as the lack of breeding with rain. The snout – vent lengths of adult spadefoots are greater in the Bonneville Basin than in other parts of the Great Basin. Utilization of permanent water sources and stimuli for emergence and breeding, as well as the larger adult size of S. intermontanus in the Bonneville Basin, are discussed in relation to the diverse precipitation patterns, the sparseness of the water sources, and the Holocene history of the Great Basin.      

Status and life history notes on the native fishes of the Alvord Basin, Oregon and 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;} Three fishes, two species of Gila, and an undescribed subspecies of cutthroat trout, are endemic to the Alvord Basin. Historically, the Alvord cutthroat trout, Salmo clarki ssp., inhabited the larger creeks of the basin but has been extirpated in pure form because of introgression with introduced rainbow trout, Salmo gairdneri. Gila boraxobius is restricted to the thermal waters of Borax Lake and its outflows in the northern part of the basin. This species is endangered because of alteration of its fragile habitat. The Alvord chub, G. alvordensis, is recorded from 16 localities throughout the basin, including springs, creeks, and reservoirs. Although G. alvordensis as a species is not in jeopardy, many populations are small and could be easily eliminated by habitat destruction or by the introduction of exotic fishes. Competition with exotic guppies, Poecilia reticulata, has extirpated the Thousand Creek Spring population of Alvord chubs. Both species of Gila are opportunistic omnivores, consuming primarily chironomids, microcrustaceans, and diatoms. The Borax Lake chub also consumed large numbers of terrestrial insects, but specialized feeding on molluscs was noted in the West Spring population of Alvord chubs. Borax Lake chubs spawn throughout the year; however, most spawning occurs in early spring. Borax Lake chubs mature at a small size, occasionally less than 30 mm standard length, and seldom live more than one year. Alvord chubs are typically much larger than the Borax Lake species and live at least into their fifth year.     

Geographical review of the historical and current status of Ospreys ( Pandion haliaetus ) in Utah

A small numbers of Ospreys ( Pandion haliaetus ) are known to have nested historically in Utah. A precise baseline figure is unavailable, but the 19th-century Osprey population in Utah probably consisted of at least 15 breeding pairs scattered in 4 geographic regions. Human persecution is believed to have caused the abandonment of nesting territories along the Wasatch Front and in the western Uinta Mountains by 1900 and 1960, respectively. Osprey populations in the southern plateaus and Green River areas, however, began increasing in the late 1970s. Several recent nesting attempts and numerous summer sightings at nontraditional and abandoned historical sites in Utah suggest the Osprey is also expanding its range in Utah. High productivity for local pairs and long-range dispersal from more northerly Osprey populations are discussed as sources for the current surge in Utah's Osprey population, which now consists of approximately 35 breeding pairs.     

Incidence of the leech Helobdella stagnalis on the Colorado River in west central Colorado

Fifty-seven fish of three genera were taken from the Colorado River in west central Colorado and examined for external parasites. No external parasites were found on Ictalurus. Seven percent of the Hybognathus and 100 percent of the Catastomus were infected with a Hirudinean of the species Helobdella stagnalis.