Wayne A. Hubert

Fish assemblages and habitat gradients in a Rocky Mountain-Great Plains stream : biotic zonation and additive patterns of community change

Abstract We examined the importance of zonation and species additions in explaining longitudinal changes in the fish assemblage of a Rocky Mountain stream that descends onto the Great Plains of Wyoming. Community changes along an elevational gradient from 2,234 to 1,230 m above mean sea level reflected a combination of zonation and downstream addition of species. Zonation was evident on a broad spatial scale as a result of stream temperatures. A coldwater trout (Salmonidae) assemblage dominated headwater reaches but was replaced by a warmwater minnow–sucker (Cyprinidae–Catostomidae) assemblage below 2,000 m. Within the warmwater zone, fish community change was due mainly to the addition of new species downstream. Headwater sites were dominated by members of the insectivore feeding guild, and other trophic guilds were added downstream. The major gradient of habitat change downstream consisted of a decrease in pool habitat and increases in stream width, depth, current velocity, turbidity, and proportion of ...

Effort Needed to Estimate Species Richness in Small Streams on the Great Plains in Wyoming

Abstract Our objective was to define the sampling effort needed with electrofishing gear or seines to capture all of the fish species present in sampling reaches on small streams of the Great Plains. The study was conducted because of recent interest in assessing the status of fishes in small streams of the Great Plains, which have lacked information that would enable sampling protocols to be developed. Based on the wetted widths (2–11 m) of sampling reaches, we defined the sampling effort needed to capture 90% and 100% of the fish species present. For electrofishing gear, sampling three 50-m-long units of the stream assured capture of 90% of the fish species present, and sampling four 50-m-units assured capture of 100%. When seines were used, sampling of four 50-m-long units captured 90% of the fish species present, and six 50-m-long units assured capture of 100%. As wetted width increased, the length of stream that needed to be sampled remained relatively constant; accordingly, the surface area of strea...

Winter Stream Conditions and Use of Habitat by Brook Trout in High-Elevation Wyoming Streams

Abstract Winter stream conditions at elevations between 2,280 and 3,205 m above mean sea level and the use of winter habitat by adult brook trout Salvelinus fontinalis above 2,990 m were evaluated in 1983–1984 and 1984–1985. Little surface ice was observed at elevations above 2,900 m, which was associated with high snow accumulation; moderate surface ice and anchor ice formation were observed at elevations from 2,550 to 2,900 m; extensive surface ice formation occurred at 2,550 m. Little snow accumulated at 2,550 m and surface ice physically excluded substantial brook trout habitat. In late fall, brook trout at elevations above 2,990 m tended to move into low-gradient areas where they remained active throughout the winter. During winter, brook trout appeared to select for areas with maximum velocities of 15 cm/s or less, measured during summer low flow, and for deeper water, but not for substrate type.

Yearling Greater Sage-Grouse Response to Energy Development in Wyoming

Abstract Sagebrush (Artemisia spp.)-dominated habitats in the western United States have experienced extensive, rapid changes due to development of natural-gas fields, resulting in localized declines of greater sage-grouse (Centrocercus urophasianus) populations. It is unclear whether population declines in natural-gas fields are caused by avoidance or demographic impacts, or the age classes that are most affected. Land and wildlife management agencies need information on how energy developments affect sage-grouse populations to ensure informed land-use decisions are made, effective mitigation measures are identified, and appropriate monitoring programs are implemented (Sawyer et al. 2006). We used information from radio-equipped greater sage-grouse and lek counts to investigate natural-gas development influences on 1) the distribution of, and 2) the probability of recruiting yearling males and females into breeding populations in the Upper Green River Basin of southwestern Wyoming, USA. Yearling males avoided leks near the infrastructure of natural-gas fields when establishing breeding territories; yearling females avoided nesting within 950 m of the infrastructure of natural-gas fields. Additionally, both yearling males and yearling females reared in areas where infrastructure was present had lower annual survival, and yearling males established breeding territories less often, compared to yearlings reared in areas with no infrastructure. Our results supply mechanisms for population-level declines of sage-grouse documented in natural-gas fields, and suggest to land managers that current stipulations on development may not provide management solutions. Managing landscapes so that suitably sized and located regions remain undeveloped may be an effective strategy to sustain greater sage-grouse populations affected by energy developments.

Expulsion of Dummy Transmitters by Rainbow Trout

Abstract Surgically implanted dummy transmitters were expelled from the body cavity of 13 of 22 rainbow trout Salmo gairdneri within 42–175 d after they were implanted. Encapsulation of the dummy transmitters by the intestine and passage through the anus appeared to be the mechanism of expulsion.

Single-Pass Electrofishing Predicts Trout Abundance in Mountain Streams with Sparse Habitat

Abstract Fish abundances in mountain streams are typically estimated over a reach with multiple-pass-removal electrofishing techniques, but such estimates are time consuming and they potentially harm fish. Recent research has indicated that a single electrofishing pass can provide an index of trout abundance in some streams, but applicable circumstances were not clarified. We sampled 30 stream reaches in northwestern Wyoming to determine if the number of trout captured with a single electrofishing pass could be used to predict trout abundance as estimated by a multiple-pass-removal maximum-likelihood model. Stream width, depth, channel slope, instream cover, and substrate were also assessed to determine their possible influences on the relationship between the number of fish captured with a single pass and multiple-pass estimates. We found that trout samples from a single electrofishing pass accurately indexed the abundance of trout in small mountain streams with little instream cover and low fish densiti...

Standard Sampling of Inland Fish: Benefits, Challenges, and a Call for Action

Abstract There are many examples of how standardization of procedures in production and data collection have led to remarkable advances in industry and science, but standardization is lacking regarding protocols for sampling fish populations in inland, freshwater systems. Reasons given why biologists often resist standardized sampling protocols include perceptions that differences in regions invalidate standard techniques; use of standard sampling is costly and reduces innovation by regional biologists; the variation already present in nature masks any gains introduced by standardization; and historical trend data is lost. We examine these reasons and provide procedures that may serve as a template by describing how development and implementation of standardized sampling protocols were achieved by the Washington Department of Fish and Wildlife. These procedures included obtaining support from high-level management within the agency and input from a wide variety of sources; emphasizing benefits to manageme...

Relations of geomorphology to stream habitat and trout standing stock in small Rocky Mountain streams

Abstract Evidence that drainage basin morphology and trout standing stock are related through a functional link between geomorphic features and stream habitat quality is presented. Numerous significant univariate correlations were found between geomorphic variables, stream habitat variables, and trout standing stock in both high-elevation forest and low-elevation rangeland streams. Canonical correlations between geomorphic variables and stream habitat variables provided insight into the form of the functional link. Multiple-regression equations predicting trout standing stock were dominated by geomorphic variables. When geomorphic variables alone were incorporated into regression models they predicted trout standing stock as accurately as did stream habitat variables.

Modified Habitat Suitability Index Model for Brown Trout in Southeastern Wyoming

Abstract The habitat suitability index (HSI) model for brown trout Salmo trutta in stream systems, developed by the U.S. Fish and Wildlife Service, was tested with data from 30 reaches on nine streams in southeastern Wyoming. The HSI was not significantly correlated (P > 0.05) with brown trout standing stock. We analyzed 14 individual suitability index variables from the HSI model plus 25 other habitat variables for their relation to standing stock. Two HSI model variables and seven of the additional variables had significant correlations with brown trout standing stock. When these nine variables were used in multiple regression analysis, the best model (R2 = 0.52) for predicting standing stock (S, kg/hectare) of brown trout included measures of cover and flow regime: S = 1.71MTCR + 114.3 V14 - 0.60; MTCR is a measure of cover availability and V14 is the average annual base flow expressed as a percent of average annual daily flow. An index of fishing pressure was also developed and found to significantly ...

Geomorphic Influences on the Distribution of Yellowstone Cutthroat Trout in the Absaroka Mountains, Wyoming

Abstract Influences of large-scale abiotic, geomorphic characteristics on distributions of Yellowstone cutthroat trout Oncorhynchus clarki bouvieri are poorly understood. We sampled 151 sites on 56 perennial streams in the Greybull–Wood river drainage in northwestern Wyoming to determine the effects of geomorphic variables on Yellowstone cutthroat trout distributions. Channel slope, elevation, stream size, and barriers to upstream movement significantly influenced the presence and absence of Yellowstone cutthroat trout. Wild populations of Yellowstone cutthroat trout were not found upstream of barriers to fish migration, at sites with channel slopes of 10% or greater, or at elevations above 3,182 m. Based on channel slope alone, logistic regression models correctly classified presence or absence of Yellowstone cutthroat trout in 83% of study sites. The addition of elevation and stream size in the models increased classification to 87%. Logistic models tested on an independent data set had agreement rates ...