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.     

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.     

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.     

Electrophoretic study of cutthroat trout populations in Utah

Thirty - nine Utah streams were sampled for cutthroat trout. Of these, 31 contain cutthroat or cutthroat / rainbow hybrid populations. By using starch gel electrophoresis, these populations were segregated into three groups. One group consisted predominately of fish from the Sevier River (of the Bonneville Basin) and Colorado drainages. A second was primarily populations from the Bear River Drainage (Bonneville Basin) as well as some scattered populations along the Wasatch Front (Bonneville Basin). The third consisted of Wasatch Front populations and populations that have hybridized with rainbow trout. Since different subspecies of cutthroat trout are native to the Colorado and Bonneville drainages, one would expect the populations from within the Bonneville Basin to be more similar to one another and less similar to the Colorado River populations. That this did not occur raises questions concerning the evolutionary relationships of the subspecies and the populations. It is clear that at least a northern (Bear River) and southern (Sevier River) form of the Bonneville cutthroat exists. The Wasatch Front may represent an intermediate zone where these two forms intergrade.         

Evidence for variability in spawning behavior of interior cutthroat trout in response to environmental uncertainty

The fluctuating characteristics (numbers, biomass, condition, and young-adult ratios) of the Lahontan (Humboldt) cutthroat trout population in Chimney Creek, Nevada, are discussed in relationship to the unpredictable and unstable habitat in which the population occurs. One possible means of adapting to environmental capriciousness, staggered spawning, occurred during 1982, and clues as to the cause of this unusual event are sought by examining the runoff hydrographs of a nearby watershed for 1981 through 1984. The management values of the environmental tolerance of these native trout with respect to restoring viable trout fisheries in degraded Great Basin streams are also considered.     

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.     

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.     

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.     

Diplostomiasis in native and introduced fishes from Yellowstone Lake, Wyoming

Totals of 101 native Yellowstone cutthroat ( Oncorhynchus clarki bouvieri ), 27 introduced lake trout ( Salvelinus namaycush ), and 40 introduced longnose sucker ( Catostomus catostomus ) from Yellowstone Lake, Wyoming, USA, were examined for eye flukes. Metacercariae of the trematode fluke Diplostomum were in vitreous humor and/or lens of 94% of Yellowstone cutthroat trout, 92% of lake trout, and 78% of longnose sucker. Longnose sucker had 7% prevalence of infection in both lens and vitreous humor of metacercariae, while Yellowstone cutthroat trout had 3% and lake trout 8%. Diplostomum spathaceum was in lens tissue of 5% of infected Yellowstone cutthroat trout and 93% of longnose sucker; Diplostomum baeri was in vitreous humor of 92% each of infected Yellowstone cutthroat trout and lake trout. Morphological characteristics indicate that a single species infected the lens of Yellowstone cutthroat trout and longnose sucker, while another species infected lake trout. Impacts of the parasite interchange between native and introduced fishes of Yellowstone Lake, Wyoming, are unknown but should be monitored each year.     

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.     

Discovery of a large population of the rare winter stonefly Isocapnia mogila Ricker in the Mad River, California (Plecoptera, Capniidae)

Isocapnia mogila , a rare winter stonefly, is found in good numbers in Humboldt County, California. In the 50 years since this species was described, very few specimens were recorded from only 4 sites in California and Oregon. Emergence seems to be higher in the fall and early winter than in the late winter and spring.     

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.     

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.     

Redescription of the Tyee Sucker, Catostomus tsiltcoosensis (Catostomidae)

We resurrect Catostomus tsiltcoosensis, the Tyee sucker of Oregon coastal rivers, from the synonymy of Catostomus macrocheilus and compare it with its congeners. Catostomus tsiltcoosensis is superficially similar to disjunctly distributed Catostomus occidentalis of the Sacramento drainage and Catostomus ardens of the Upper Snake River and Bonneville Basin. However, the gill raker structure, wide frontoparietal fontanelle, location of the ninth cranial foramen, scale radii patterns, and cytochrome b sequences clearly align C. tsiltcoosensis with C. macrocheilus rather than C. occidentalis. Differences in counts of infraorbital pores and dorsal fin rays, in body depth proportions, and in cytochrome b sequences distinguish C. tsiltcoosensis and C. macrocheilus. Within C. tsiltcoosensis, specimens from each of the 4 main drainages (north to south—Siuslaw, Umpqua, Coos, and Coquille) were reciprocally monophyletic based on cytochrome b data but showed no differences in the morphological features examined. Both C. tsiltcoosensis and another Oregon coastal taxon Catostomus rimiculus were paraphyletic based on cytochrome b. Although such discordant mitochondria results can be due to introgression, incomplete lineage sorting, and paralogy, other evidence suggests that introgression and lateral transfer of mitochondria explains the cytochrome b pattern in C. rimiculus. We speculate that lateral transfer might also be responsible for the pattern in C. tsiltcoosensis, except that the Coquille River population appears not to have been included in recent transfers.     

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.     

Status and conservation of salmonids in relation to hydrologic integrity in the Greater Yellowstone Ecosystem

Native salmonid status was evaluated with an index quantifying distribution and abundance of cutthroat trout ( Oncorhynchus clarki ) and grayling ( Thymallus arcticus ) in 41 watersheds comprising the Greater Yellowstone Ecosystem. We assessed hydrologic integrity with a percentile-based index measuring cumulative effects of reservoirs, surface water withdrawals, and consumptive water use. Status of native salmonids was poor in 70% of the watersheds; exceptions occurred in a north-south core extending from the Upper Yellowstone southward through the national parks to Bear Lake. Hydrologic integrity was highest in headwater areas and lowest in lower-elevation watersheds. Status of native and nonnative salmonid populations currently existing in the ecosystem was positively correlated with hydrologic integrity ( r = 0.58), indicating that the hydrologic index performed well on a watershed scale in quantifying suitability of stream environments for salmonids. However, native trout status and hydrologic integrity were similarly correlated ( r = 0.63) only when watersheds receiving the lowest possible native salmonid index score were removed from analysis because these watersheds were uniformly distributed across hydrologic integrity. We infer that nonphysical factors such as interactions with introduced fish species have played an important role in the disappearance of native salmonids. The highest priority for conservation is preservation of core watersheds, where both hydrologic integrity and native trout status are high. Restoration opportunities exist in the Teton, Idaho Falls, Willow Creek, Central Bear, and Bear Lake watersheds, where viable cutthroat trout populations remain but are threatened by habitat degradation.     

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.     

Different life histories of brook trout populations invading mid-elevation and high-elevation cutthroat trout streams in Colorado

Brook Trout ( Salvelinus fontinalis ), native to eastern North America, have invaded many montane cold-water systems of western North America, and these invasions are implicated in the decline of native cutthroat trout ( Oncorhynchus clarki ). If fisheries biologists are to be effective in managing brook trout invasions, demographic models that predict invasion success will need to incorporate life history variation in different environments. We tested whether brook trout populations invading streams at 2 different elevations varied in life history characteristics that influence population dynamics and potential invasion success. In the high-elevation stream (3195 m), water temperatures were colder and brook trout apparently grew more slowly (i.e., had shorter lengths-at-age), became sexually mature 2 years later, and had life spans 2 to 3 times longer than those in the mid-elevation stream (2683 m). This flexibility in life history may allow brook trout to maximize their chance of establishment and invasion success among elevations. We propose that in mid-elevation streams fast growth and early maturity maximize fitness and can lead to rapid establishment and high population growth rates. In high-elevation streams, slow growth, later maturity, and a long reproductive life span may allow brook trout to successfully establish populations in these marginal habitats where recruitment is often poor.     

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.        

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

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