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Most subspecies of interior cutthroat trout Oncorhynchus clarki have suffered dramatic declines in range and number. We assessed the status of genetically pure Yellowstone cutthroat trout O. clarki bouvieri on predominantly public lands in three major watersheds of northwestern Wyoming (Greybull River and North and South Forks of the Shoshone River) between 1994 and 1997. These river basins encompass the majority of remaining habitat outside of Yellowstone National Park with potential to contain Yellowstone cutthroat trout, and little information on them was available. Only 26% of the 104 streams found to contain trout still support genetically pure Yellowstone cutthroat trout. Extant Yellowstone cutthroat trout occupied 245 of 822 km of the perennial streams that contained trout, suggesting native trout have been displaced by or hybridized with exotic salmonids in nearly three‐quarters of the available habitat in these watersheds. The four remaining populations were widely separated in the watersheds and had populations that ranged from 900 to 23,000 age‐1 and older individuals and that appeared genetically and demographically viable. However, because the threats of hybridization and competition remain, the current cutthroat trout populations cannot be considered secure or likely to persist over the long term. Yellowstone cutthroat trout have suffered larger than expected declines in their distribution in Wyoming outside of Yellowstone National Park largely because of nonnative salmonid introductions and invasions. We recommend immediate management intervention to control exotic salmonids and reestablish large, genetically pure, allopatric populations of Yellowstone cutthroat trout.

Influences of large-scale abiotic, geomorphic characteristics on distributions of Yellowstone cutthroat trout Oncorhynchus clarki bouvieri arc 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 Yellowslone 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 as high as 91% between actual and predicted fish presence. Large-scale geomorphic variables influence Yellowstone cutthroat trout distributions, and logistic functions can predict these distributions with a high degree of accuracy.

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Scales and otoliths (sagittae) were collected from black crappies Pomoxis nigromaculatus sampled during the spring of 1991 in Red Plum Reservoir and Roy Lake, South Dakota. Red Plum Reservoir contained a slow‐growing black crappie population, whereas Roy Lake had a fast‐growing population. Annuli in scales and otoliths were identified independently by three readers. Within‐structure (i.e., among‐reader) and between‐structure agreements in both population samples were 94% or greater for both scales and otoliths from fish of all ages. Our results indicated that for black crappies from South Dakota waters, precision of ages determined from scales and otoliths was similar.

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The piscicide rotenone is commonly used to remove nonnative fishes from natural aquatic systems. While the effects of rotenone on fish are well documented, the effects of this chemical on amphibians are less well known. We determined the toxicity of the rotenone formulation CFT Legumine (5% rotenone) to three ages—Gosner age ranges 21–25, 30–35, and 40–45—of tadpoles of the Columbia spotted frog Rana luteiventris and the boreal toad Anaxyrus boreas under laboratory conditions. Tadpoles of both species were exposed to 0.1, 0.5, and 1.0 mg/L CFT Legumine (0.005, 0.025, and 0.050 mg/L rotenone, respectively) in static, 96‐h exposure trials; surviving individuals were placed in rotenone‐free water and raised until metamorphosis. In an additional experiment, Columbia spotted frog tadpoles were exposed to 1.0 mg/L CFT Legumine for 1, 2, 3, or 4 h before being placed in rotenone‐free water for the duration of a 96‐h exposure period. Tadpole mortality increased with increases in CFT Legumine concentration and exposure period. Individuals exposed to 1.0 mg/L of product experienced significantly greater mortality than did control tadpoles (P < 0.001), with 99–100% mortality occurring in the youngest age‐group (Gosner 21–25) in both species. In Columbia spotted frog tadpoles, mortality decreased as age increased, while age did not affect mortality in boreal toad tadpoles. Rotenone produced no biologically significant effects on growth or metamorphosis. Our findings suggest that the use of 1.0 mg/L CFT Legumine to remove nonnative fish may cause significant mortality to larval amphibians if they are exposed for 96 h; exposures to lower dosages (0.5 mg/L of product) or for shorter durations (≤4 h), however, resulted in less mortality. Fisheries managers can use these results to improve amphibian conservation in fish restoration areas and reduce the impacts on larval amphibian populations.

Translocations are frequently used to increase the abundance and range of endangered fishes. One factor likely to affect the outcome of translocations is fish movement. We introduced embryos from five Westslope Cutthroat Trout Oncorhynchus clarkii lewisi populations (both hatchery and wild) at five different locations within a fishless watershed. We then examined the movement of age‐1 and age‐2 fish and looked for differences in movement distance among source populations and among introduction sites; we also examined the interactions among age, population, and introduction site. At age 1, most individuals (90.9%) remained within 1,000 m their introduction sites. By age 2, the majority of individuals (58.3%) still remained within 1,000 m of their introduction site, but considerably more individuals had moved downstream, some more than 6,000 m from their introduction site. We observed a significant interaction between age and source population (F 4, 1077 = 15.45, P < 0.0001) as well as between age and introduction site (F 41, 1077 = 11.39, P < 0.0008), so we presented results in the context of these interactions. Within age‐groups, we observed differences in movement behavior among source populations and among donor populations of Westslope Cutthroat Trout. We discuss these findings in light of previous research on juvenile salmonid movement.Received April 20, 2012; accepted June 3, 2013