Carter G. Kruse

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...

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 ...

Status of Yellowstone Cutthroat Trout in Wyoming Waters

Abstract 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 water...

Proposed Standard Weight (Ws ) Equations for Interior Cutthroat Trout

Abstract We developed standard weight (Ws ; length-specific standard weight for the species) equations for inland cutthroat trout Oncorhynchus clarki using the regression-line-percentile technique. Length and weight data from samples of 117 cutthroat trout populations (48 lentic and 69 lotic) over the interior range of the species were used. Separate Ws equations were developed for lentic and lotic populations, as well as an overall equation. Relative weight (Wr ; individual weight/Ws ) values did not change systematically with increasing fish length. No significant differences in mean Wr were found among subspecies of cutthroat trout. Differences between lotic and lentic populations suggested the need for two separate equations.

Toxicity of the Piscicide Rotenone to Columbia Spotted Frog and Boreal Toad Tadpoles

Abstract 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 concentratio...

Performance of Juvenile Cutthroat Trout Translocated as Embryos from Five Populations into a Common Habitat

AbstractThe distributions of most native trout species in western North America have been severely reduced, and conservation of many of these species will require translocation into vacant habitats following removal of nonnative species. A critical question managers have is “Does it matter which donor sources are used for these translocations?” We present a case study that addressed this question for a large native trout translocation project in Montana. We introduced embryos from five source populations of Westslope Cutthroat Trout Oncorhynchus clarkii lewisi to a large, fishless watershed in Montana following removal of nonnative fish with piscicides. Source populations providing embryos for translocations were three nearby ( 350 km from the translocation site), and a population in captivity for one generation comprised of i...

Effects of CFT Legumine (5% Rotenone) on Tadpole Survival and Metamorphosis of Chiricahua Leopard Frogs Lithobates chiricahuensis, Northern Leopard Frogs L. pipiens, and American Bullfrogs L. catesbeianus

AbstractAmphibians may experience collateral effects if exposed to CFT Legumine (5% rotenone), a piscicide that is used to remove invasive fish. A series of 48-h static toxicity tests assessed the acute effects of CFT Legumine on multi-aged tadpoles of the federally listed Chiricahua leopard frog Lithobates chiricahuensis, the widespread northern leopard frog L. pipiens, and the increasingly invasive American bullfrog L. catesbeianus. At the earliest Gosner stages (GS 21–25), Chiricahua leopard frogs were more sensitive to CFT Legumine (median lethal concentration [LC50] = 0.41–0.58 mg/L) than American bullfrogs (LC50 = 0.63–0.69 mg/L) and northern leopard frogs (LC50 = 0.91 and 1.17 mg/L). As tadpoles developed (i.e., increase in GS), their sensitivity to rotenone decreased. In a separate series of 48-h static nonrenewal toxicity tests, tadpoles (GS 21–25 and GS 31–36) of all three species were exposed to piscicidal concentrations of CFT Legumine (0.5, 1.0, and 2.0 mg/L) to assess postexposure effects on...