Mountain Sucker Research Articles

Rapid colonisation post‐displacement contributes to native fish resilience

AbstractNative freshwater fish are experiencing global declines. Determining what drives native fish resilience to disturbance is crucial to understanding their persistence in the face of multiple stressors. Fish colonisation ability may be one factor affecting population resilience after disturbance. We conducted displacement experiments in headwater streams in Wyoming, USA, to evaluate mottled sculpin (Cottus bairdii) and mountain sucker (Catostomus platyrhynchus) colonisation ability. Specifically, we (1) determined whether fish could colonise sites rapidly after displacement, (2) evaluated site‐level factors affecting colonisation, and (3) compared species‐level differences in movement and colonisation capabilities. Mountain sucker recovered to pre‐displacement abundances within 6–11 weeks, but mottled sculpin were still at slightly reduced abundances. For both species, the majority of colonists were unmarked new individuals and size–structure was similar to pre‐displacement size–structure. Fish colonisation was best predicted by pre‐displacement abundance and an interaction between per cent riparian cover and species identity. The slower colonisation rate of mottled sculpin may relate to movement ability as average daily movement rate and movement extent were significantly greater for mountain sucker. Our results demonstrate that colonisation is one mechanism allowing fish populations to be resilient in the face of disturbance and that species' traits provide insight into fish colonisation capabilities. Experimental approaches provide mechanistic insight into colonisation dynamics, enhancing our understanding of native fish resilience in degraded stream ecosystems and their response to restoration actions.

Certain detection of uncertain taxa: eDNA detection of a cryptic mountain sucker (Pantosteus jordani) in the Upper Missouri River, USA

AbstractA lineage of the Mountain Sucker species complex (Pantosteus jordani) exists as a genetically and morphologically distinct taxon restricted to the Missouri River basin. This species is thought to be declining throughout its range and is assumed to be extirpated from the southern portion of its distribution. We developed a quantitative PCR‐based environmental DNA assay for P. jordani to help define and monitor its current range. The assay is both specific to P. jordani and sensitive to low amounts of DNA, with a detection limit of 10 DNA copies per reaction. In vitro experiments involved testing DNA from twenty tissue samples, collected from the Missouri River basin in Montana and Wyoming. The assay efficiently detected DNA of all P. jordani samples and did not amplify DNA of any closely related nontarget species. Additionally, 29 environmental DNA samples were taken in 19 waterbodies within P. jordani range and its presence or absence was determined prior to sampling at six of 29 sites. All sites where P. jordani was known absent produced negative results, and all sites where it was known present were confirmed with environmental DNA detections. The new assay was able to detect P. jordani at ten sites which were not previously known to contain individuals, demonstrating that this tool has the potential to rapidly expand the current understanding of this taxon's distribution.

Warmer temperatures interact with salinity to weaken physiological facilitation to stress in freshwater fishes.

Management of stressors requires an understanding of how multiple stressors interact, how different species respond to those interactions and the underlying mechanisms driving observed patterns in species’ responses. Salinization and rising temperatures are two pertinent stressors predicted to intensify in freshwater ecosystems, posing concern for how susceptible organisms achieve and maintain homeostasis (i.e. allostasis). Here, glucocorticoid hormones (e.g. cortisol), responsible for mobilizing energy (e.g. glucose) to relevant physiological processes for the duration of stressors, are liable to vary in response to the duration and severity of salinization and temperature rises. With field and laboratory studies, we evaluated how both salinity and temperature influence basal and stress-reactive cortisol and glucose levels in age 1+ mottled sculpin (Cottus bairdii), mountain sucker (Catostomus platyrhynchus) and Colorado River cutthroat trout (Oncorhynchus clarki pleuriticus). We found that temperature generally had the greatest effect on cortisol and glucose concentrations and the effect of salinity was often temperature dependent. We also found that when individuals were chronically exposed to higher salinities, baseline concentrations of cortisol and glucose usually declined as salinity increased. Reductions in baseline concentrations facilitated stronger stress reactivity for cortisol and glucose when exposed to additional stressors, which weakened as temperatures increased. Controlled temperatures near the species’ thermal maxima became the overriding factor regulating fish physiology, resulting in inhibitory responses. With projected increases in freshwater salinization and temperatures, efforts to reduce the negative effects of increasing temperatures (i.e. increased refuge habitats and riparian cover) could moderate the inhibitory effects of temperature-dependent effects of salinization for freshwater fishes.

Anthropogenic land‐use change intensifies the effect of low flows on stream fishes

Abstract As ecosystems experience simultaneous disturbances, it is critical to understand how multiple stressors interact to affect ecological change. Land‐use change and extreme flow events are two important stressors that could interact to affect fish populations. We evaluated the individual and interactive effects of discharge and land‐use change associated with oil and natural gas development on populations of two stream fishes over a 7‐year period. We used repeated‐state (i.e. abundance trends) and rate (i.e. colonization and persistence) responses to advance our understanding of flow‐ecology relationships in a multiple‐stressor framework. Overall, fish abundance, colonization and persistence declined as discharge decreased. The effect of land‐use change associated with oil and natural gas development differed between species, with the abundance of Mottled Sculpin declining and Mountain Sucker increasing as land‐use change increased. We found both synergistic and antagonistic interactions between discharge and land‐use change. Land‐use change intensified the effect of low flows for Mottled Sculpin and lead to greater variability in responses to flow for Mountain Sucker. These differences between species' responses are likely due to differences in their physiological tolerances and behavioural adaptations to disturbance. Synthesis and applications. Our research provides empirical evidence for the complex interactions that can arise between discharge and anthropogenic land‐use change. Management efforts to reduce inputs of sediments and chemical contaminants associated with land‐use change (e.g. silt fences, vegetative buffers) and promote quality refuge habitats (i.e. in‐stream habitat restoration) could help mitigate the negative effects of low‐flow extremes on stream fishes. Further development of flow‐ecology relationships in a multiple‐stressor framework will help guide management of stream fishes, and provide a better understanding of the mechanisms underlying responses of different species.

A mechanistic understanding of ecological responses to land‐use change in headwater streams

AbstractAnthropogenic activities, such as oil and natural gas development (ONGD), have significantly altered the landscape. It is often challenging to identify the mechanistic processes underlying ecological responses to land‐use change (LUC). In aquatic ecosystems, alterations to habitat and food availability and water quality associated with increased LUC are key mechanistic pathways that deserve management consideration. We used structural equation modeling to evaluate how LUC associated with ONGD could influence macroinvertebrate and fish across 40 sites in six headwater streams in the Wyoming Range of the Upper Green River Basin, Wyoming. The most important mechanistic pathway varied, but responses were frequently driven by a direct effect of LUC or related to changes in food availability and water quality. Habitat complexity was the least important mechanistic pathway in our models. Our results also highlight that responses may reflect an organism's degree of habitat or resource specialization and/or sensitivity to changes in water quality. Habitat pathways were more important for habitat specialists (e.g., Mottled Sculpin, Cottus bairdii), food pathways were more important for food specialists (e.g., Colorado River Cutthroat Trout, Oncorhynchus clarki pleuriticus; Mountain Sucker, Catostomus platyrhynchus), and sensitivity to increased salinity was important for intolerant species (e.g., O. clarki, C. bairdii, and predatory macroinvertebrates). Continued identification of the specific mechanisms underlying species’ responses to increased LUC will aid in the conservation of ecologically and economically important species.

Evaluating relationships between native fishes and habitat in streams affected by oil and natural gas development

Oil and natural gas (ONG) development can affect aquatic ecosystems through water contamination, water withdrawals and disturbance of soil and vegetation (surface disturbance) from infrastructure development. Research on how these potential sources of watershed and aquatic ecosystem impairment can affect fish assemblages is limited. Fish–habitat relationships were evaluated across stream sites experiencing differing levels of ONG development. Colorado River cutthroat trout, Oncorhynchus clarkii pleuriticus (Cope), and mottled sculpin, Cottus bairdii Girard, presence and abundance were associated with habitat conditions predominantly found in the less disturbed streams, such as higher proportion of shrub cover, greater stream depths and gravel substrate. Mountain sucker, Catostomus platyrhynchus (Cope), appeared to be a habitat generalist and was able to persist in a wide range of conditions, including degraded sites. Natural resource managers can use habitat preferences of these fish species to establish the development plans that mitigate negative effects of ONG development by protecting the aquatic habitats they rely upon.

Lacustrine Spawning by Mountain Suckers (Catostomus platyrhynchus) on Boulder Mountain, Utah

Abstract. Facultative spawning in lakes is an uncommon and notable behavior among catostomids and other fish species that typically spawn in streams. I describe what may be the first documented case of lake-spawning behavior by mountain suckers (Catostomus platyrhynchus).

Habitat and Fish Assemblage Associations and Current Status of Northern Leatherside ChubLepidomeda copeiin Western Wyoming

Human activities have extensively altered native fish assemblages and their habitats in the western United States. Conservation and restoration for long-term persistence of these fishes requires knowledge of their distributional patterns and life history requirements. Northern leatherside chub Lepidomeda copei (hereafter northern leatherside) is a cyprinid native to the Snake and Bear River Basins of Wyoming, Idaho, Nevada, and Utah, and it is believed to have declined in distribution relative to historical records. To address information gaps in the species' ecology and assess its status in the state, the objectives of this study were first to document the distribution (2010–2011) of northern leatherside in Wyoming and then to examine habitat factors related to the entire fish assemblage and to evaluate specific habitat associations of northern leatherside in the Bear River Basin, Wyoming. In the Bear River and Upper Snake River Basins, we documented the distribution of northern leatherside and compared it to the previously known distribution. Across the Bear River Basin, we used habitat measurements to assess abiotic features related to the distribution and abundance of northern leatherside. Northern leatherside was found across the Bear River Basin and was present in 2 streams each in the Upper Snake River and Green River Basins in Wyoming. Populations in Wyoming appear to represent the core of northern leatherside range, and our work provided a finer-scale delineation of the species' occurrence. Northern leatherside was collected from a variety of habitats, but multivariate analyses and occurrence modeling indicated it was associated with increased channel depth and depth variability, and positively associated with other native fishes (including mountain sucker Catostomus platyrhynchus, redside shiner Richardsonius balteatus, and speckled dace Rhinichthys osculus). These findings on the distribution and ecology of northern leatherside provide important new information to assist successful management and conservation efforts within Wyoming and across the species' range.

The Intestinal Parasites of an Assemblage of Stream Fishes in Central Utah

Abstract. Parasite communities of stream fish assemblages in the western United States are poorly known. We investigated the intestinal parasites of an assemblage of stream fishes in Spanish Fork River in central Utah, USA. Two species, mottled sculpin (Cottus bairdii) and redside shiner (Richardsonius balteatus), had no observable parasites. In the other 3 species, southern leatherside chub (Lepidomeda aliciae), mountain sucker (Catostomus platyrhynchus), and longnose dace (Rhinichthys cataractae), we identified metacercia of an unidentified trematode. We found adult cestodes in southern leatherside chub only. Prevalence and intensity of parasites was highest in southern leatherside chub. Reasons for differential prevalence and intensity of parasites among host fish species are unknown, but there seems to be no relationship to trophic position or habitat use in this fish community.

Genetic structure of a disjunct peripheral population of mountain sucker Pantosteus jordani in the Black Hills, South Dakota, USA

A peripheral population of mountain sucker, Pantosteus jordani, located in the Black Hills of South Dakota, USA, represents the eastern-most range of the species and is completely isolated from other populations. Over the last 50 years, mountain sucker populations have declined in the Black Hills, and now only occur in 40 % of the historic local range, with densities decreasing by more than 84 %.We used microsatellite DNA markers to estimate genetic diversity and to assess population structure across five streams where mountain suckers persist. We evaluated results in the context of recent ecological surveys to inform decisions about mountain sucker conservation. Significant allele frequency differences existed among sample streams (Global FST = 0.041) but there was no evidence of isolation by distance. Regionally, genetic effective size, Ne, was estimated to be at least 338 breeding individuals, but Ne within streams was expected to be less. Despite almost complete demographic isolation and reduced population size, there appears to be little evidence of inbreeding, but genetic drift and local isolation due to fragmentation probably best explains genetic structure in this peripheral mountain sucker population. Recommended strategies for population enhancement include restoration of stream connectivity and habitat improvement. Moreover, repatriation and assisted movement (i.e., gene flow) of fishes should maximize genetic diversity in stream fragments in the Black Hills region.

Factors from multiple scales influence the distribution and abundance of an imperiled fish – mountain sucker in the Black Hills of South Dakota, USA

An understanding of the factors associated with the distribution of fishes is fundamental to stream ecology, and can be used to assess and prioritize conservation areas. Mountain sucker Catostomus platyrhynchus is generally stable across its range in Western North America, but recent studies have documented declines at finer spatial scales near the periphery of its range, including the Black Hills of South Dakota. Despite its wide-ranging distribution, little information exists on mountain sucker autecology or community dynamics. The objective of this study was to evaluate the hierarchical influence of physical and biological variables on the distribution and abundance of mountain sucker in streams of the Black Hills, South Dakota, USA. We evaluated the support for candidate models that incorporated multiple spatial scales and potential biotic interactions to model mountain sucker presence and abundance using an information theoretic approach. Mountain sucker presence was best explained by a combination of reach-scale habitat and fish assemblage variables, including a negative influence of trout abundance. Mountain sucker abundance increased with periphyton coverage, a food resource. These models increase understanding of mountain sucker ecology, can be used to assess and prioritize areas of conservation interest for this native fish in the Black Hills, and can identify management actions that will provide the most effective conservation strategies for this species.

Estimating the Ages of Mountain SuckerCatostomus platyrhynchusfrom the Black Hills: Precision, Maturation, and Growth

Although mountain sucker Catostomus platyrhynchus is considered secure across its range, it has declined in parts of its range and is listed in South Dakota as a species of greatest conservation need. To our knowledge, no research has identified which calcified structure provides the most precise age estimates for mountain sucker, and little is known about mountain sucker population dynamics. To identify which structure provided the most precise age estimates, we compared age estimates from scales, sectioned pectoral fin rays, whole asteriscus otoliths, and polished asteriscus otoliths collected from 110 mountain sucker from 2 creeks in the Black Hills of South Dakota. Additionally, we quantified growth, age, and size at maturation for one population of mountain sucker in the Black Hills. Polished otoliths had the greatest precision of the 4 structures used, followed by sectioned pectoral fin rays. Mountain sucker reached an average size of 100 mm total length (TL) during their fourth growing season and reached an average maximum attainable size of 219 mm TL. Mountain sucker began to mature at age 3, with nearly all being mature by age 5. In the Black Hills, the shortest mature male was 95 mm TL and the shortest mature female was 101 mm TL. We recommend using polished otoliths to estimate the ages of mountain sucker. If a nonlethal structure is desired to estimate the ages of mountain sucker, we recommend using sectioned pectoral fin rays. Future research should be directed to fill the many knowledge gaps in the biology and ecology of mountain sucker (e.g., juvenile habitat use in the Black Hills). As these knowledge gaps are addressed, management actions could be taken to conserve this species in the parts of its range where it is declining.

Comparative Swimming Performance of Five Catostomus Species and Roundtail Chub

Abstract.—Decreased habitat connectivity and competition with nonnative species have led to declines of many freshwater fishes. An understanding of swimming performance can aid in the conservation of these fishes; however, acquiring sufficient numbers of rare and threatened species to perform swimming studies can be logistically challenging and ecologically costly. In order to determine whether swimming data for common sucker species may be substituted for that of similar but rare sucker species, we compared the swimming abilities of two rare western catostomids, Bluehead Sucker Catostomus discobolus and Flannelmouth Sucker C. latipinnis, as well as one catostomid with a less well understood status, Mountain Sucker C. platyrhynchus, with those of the common White Sucker C. commersonii and Longnose Sucker C. catostomus. We also examined Roundtail Chub Gila robusta because they are often included in conservation efforts involving Bluehead Sucker and Flannelmouth Sucker. The critical swimming velocities (Ucrit), standardized by body length, of Bluehead Sucker and Longnose Sucker differed significantly from those of White Sucker. However, there was no significant difference between the Ucrit of Mountain Sucker, Flannelmouth Sucker, and White Sucker. During constant acceleration trials, Bluehead Sucker exhibited the greatest swimming ability, reaching a mean maximum velocity of 4.56 ± 1.28 body lengths per second (BL/s; mean ± SD), followed by Mountain Sucker (3.56 ± 0.57 BL/s), White Sucker (3.28 ± 0.90 BL/s), Longnose Sucker (2.97 ± 0.31 BL/s), and Flannelmouth Sucker (2.22 ± 0.42 BL/s). Additionally, key behavioral differences in the swimming behaviors of the fishes studied were observed. We conclude that swimming performance data for common White Sucker should not be used in place of data for rarer species. Comprehensive swimming studies should be conducted on individual sucker species before implementing conservation strategies involving fish passageways or barriers.Received November 6, 2013; accepted February 28, 2014

Shape variation in a benthic stream fish across flow regimes

Evolution of fish body shapes in flowing and non-flowing waters have been examined for several species. Flowing water can select for fish body shapes that increase steady swimming efficiency, whereas non-flowing water can favor shapes that increase unsteady swimming efficiency. Benthic stream fishes often use areas near the substrate that exhibit reduced or turbulent flow, thus it is unclear which swimming forms would be favored in such environments, and how shape might change across flow regimes. To test the relationship between fish body shape and flow regime in a benthic stream fish, we used geometric morphometric techniques to characterize lateral body shape in mountain sucker (Catostomus platyrhynchus) across flow rates, using stream gradient as an indicator of stream flow. Mountain suckers from low-flow environments were more streamlined, consistent with steady swimming body shapes, whereas mountain suckers from high flows had deeper bodies, consistent with unsteady swimming body shapes. In addition, smaller individuals tended to have more robust body shapes. These patterns are opposite to those predicted for stream fishes in the mid-water column. The benthic stream environment represents a distinct selective environment for fish shape that does not appear to conform to the simple dichotomy of flowing versus non-flowing water.

Influence of Introgression and Geological Processes on Phylogenetic Relationships of Western North American Mountain Suckers (Pantosteus, Catostomidae)

Intense geological activity caused major topographic changes in Western North America over the past 15 million years. Major rivers here are composites of different ancient rivers, resulting in isolation and mixing episodes between river basins over time. This history influenced the diversification of most of the aquatic fauna. The genus Pantosteus is one of several clades centered in this tectonically active region. The eight recognized Pantosteus species are widespread and common across southwestern Canada, western USA and into northern Mexico. They are typically found in medium gradient, middle-elevation reaches of rivers over rocky substrates. This study (1) compares molecular data with morphological and paleontological data for proposed species of Pantosteus, (2) tests hypotheses of their monophyly, (3) uses these data for phylogenetic inferences of sister-group relationships, and (4) estimates timing of divergence events of identified lineages. Using 8055 base pairs from mitochondrial DNA protein coding genes, Pantosteus and Catostomus are reciprocally monophyletic, in contrast with morphological data. The only exception to a monophyletic Pantosteus is P. columbianus whose mtDNA is closely aligned with C. tahoensis because of introgression. Within Pantosteus, several species have deep genetic divergences among allopatric sister lineages, several of which are diagnosed and elevated to species, bringing the total diversity in the group to 11 species. Conflicting molecular and morphological data may be resolved when patterns of divergence are shown to be correlated with sympatry and evidence of introgression.

Long Term Trends and Outlook for Mountain Sucker in the Black Hills of South Dakota

The extirpation of native fishes is a major concern in North America, and an understanding of population trends of imperiled fishes is critical to their management and conservation. Mountain sucker Catostomus platyrhynchus is a stream fish native to the Intermountain Region of western North America, and populations in the Black Hills of South Dakota represent the easternmost range of the species. Recently, stream surveys raised concerns about the status of mountain sucker populations in South Dakota. The purpose of this study was to document the current distribution of mountain sucker in the Black Hills of South Dakota for comparison with historic records. We analyzed stream fisheries survey data collected between 1960 and 2010 and found that mountain sucker density generally declined at three nested spatial scales: sample reach, stream, and watershed. At 14 sample reaches and two streams mountain sucker appear extirpated, whereas in remaining areas they persist in varying densities. In 2009–2010, populations exceeding densities of 0.01 fish·m−2 persisted only in Whitewood, Elk, Boxelder, and Bear Butte Creeks, and tributaries to Upper Rapid Creek. Our study documents the decline of a native fish in the Black Hills of South Dakota, and a comprehensive ecosystem management approach is needed to mitigate further loss of mountain sucker and co-occurring native species, while at the same time maintaining a highly valued non-native salmonid fishery.

An Assessment of the Lethal Thermal Maxima for Mountain Sucker

Temperature is a critical factor in the distribution of stream fishes. From laboratory studies of thermal tolerance, fish ecologists can assess whether species distributions are constrained by tolerable thermal habitat availability. The objective of this study was to use lethal thermal maxima (LTM) methodology to assess the upper thermal tolerance for mountain sucker Catostomus platyrhynchus, a species of greatest conservation need in the state of South Dakota. Adult fish were captured from wild populations in the Black Hills of South Dakota and acclimated to 20, 22.5, and 25 °C. Four endpoints (3 sublethal, 1 lethal) were recorded, with death being the most precise (lowest SE, easily discernible). The LTM for mountain sucker was 34.0 °C at 25 °C acclimation, 33.2 °C at 22.5 °C acclimation, and 32.9 °C at 20 °C acclimation. Compared to co-occurring species in the Black Hills, the LTM of mountain sucker is higher than that of salmonids but lower than that of 3 cypriniforms. Mountain sucker LTM is intermediate compared to other species in the family Catostomidae. These results suggest that the mountain sucker is not currently limited by water temperatures in the Black Hills but may be affected by stream warming as a result of climate change.

New Host and Locality Records for Gyrodactylus wardi Kritsky and Mizelle, 1968 (Monogenoidea: Gyrodactylidae), from Suckers, Catostomus spp. (Catostomidae), in Idaho

Gyrodactylus wardi Kritsky and Mizelle, 1968, is reported from the external surfaces of the mountain sucker, Catostomus platyrhynchus, and Utah sucker, Catostomus ardens, from the Cub River in Idaho. This report represents new host and locality records for G. wardi. Unidentified species of Gyrodactylus also occur on the external surfaces of the Utah sucker in Idaho. A previously published report of Gyrodactylus atratuli Putz and Hoffman, 1957, on Catostomus catostomus in Labrador is incorrect and represents G. wardi.

Irrigation Canals as Sink Habitat for Trout and Other Fishes in a Wyoming Drainage

AbstractIrrigation canals can be a major source of mortality for fish in the Rocky Mountain region. Our study looked at how fish were affected by the irrigation canal system in the Smiths Fork, a tributary to the Bear River in western Wyoming. There are two native species of conservation concern in the Smiths Fork drainage: Bonneville cutthroat trout Oncorhynchus clarkii utah and northern leatherside chub Lepidomeda copei. Our objectives were to determine the relative abundance of each species within the canals and the fate of trout (Bonneville cutthroat trout and brown trout Salmo trutta) that enter canals. During the summer of 2003 we sampled 30 sites within the Covey Canal system, which is the largest canal system withdrawing water from the Smiths Fork. Because fish were observed to accumulate at certain spots in the canal system, we developed a sampling scheme that incorporated both random sample sites and sites known to attract fish. We estimated that between 6,300 and 10,400 fish encompassing 10 species were entrained in this canal system. The two most abundant species were speckled dace Rhinichthys osculus (29% of all fish) and mountain sucker Catostomus platyrhynchus (37% of all fish). Bonneville cutthroat trout and northern leatherside chub each comprised 2% of the total entrained fish. We implanted 30 Bonneville cutthroat trout and 13 brown trout with radio transmitters to determine whether entrained trout could leave the canal system when water levels were reduced in late summer. We found that 77% of the transmitter‐implanted fish died within the canals, indicating that this system functions as sink habitat for Bonneville cutthroat trout and brown trout. Based on this mortality rate, we estimated that 120 Bonneville cutthroat trout (95% confidence interval, 75‐165) and 299 brown trout (280‐317) perished in the Covey Canal system during the summer of 2003.

Distribution modelling to guide stream fish conservation: an example using the mountain sucker in the Black Hills National Forest, USA

Abstract Conservation biologists need tools that can utilize existing data to identify areas with the appropriate habitat for species of conservation concern. Regression models that predict suitable habitat from geospatial data are such a tool. Multiple logistic regression models developed from existing geospatial data were used to identify large‐scale stream characteristics associated with the occurrence of mountain suckers (Catostomus platyrhynchus), a species of conservation concern, in the Black Hills National Forest, South Dakota and Wyoming, USA. Stream permanence, stream slope, stream order, and elevation interacted in complex ways to influence the occurrence of mountain suckers. Mountain suckers were more likely to be present in perennial streams, and in larger, higher gradient streams at higher elevations but in smaller, lower gradient streams at lower elevations. Applying the logistic regression model to all streams provided a way to identify streams in the Black Hills National Forest most likely to have mountain suckers present. These types of models and predictions can be used to prioritize areas that should be surveyed to locate additional populations, identify stream segments within catchments for population monitoring, aid managers in assessing whether proposed forest management will potentially have impacts on fish populations, and identify streams most suitable for stream rehabilitation and conservation or translocation efforts. When the effect of large brown trout (Salmo trutta) was added to the best model of abiotic factors, it had a negative effect on the occurrence of mountain suckers. Negative effects of brown trout on the mountain sucker suggest that management of recreational trout fisheries needs to be balanced with mountain sucker conservation in the Black Hills. However, more spatially explicit information on brown trout abundance would allow managers to understand where the two species interact and where recreational fisheries need to be balanced with fish conservation. Copyright © 2008 John Wiley & Sons, Ltd.