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Fort Collins, CO, United States

Diedrich D.J.,Western Washington University | Diedrich D.J.,Colorado School of Mines | Sofield R.M.,Western Washington University | Ranville J.F.,Colorado School of Mines | And 3 more authors.
Archives of Environmental Contamination and Toxicology | Year: 2015

A series of toxicity tests were conducted to investigate the role of chronological age on zinc tolerance in juvenile brown trout (Salmo trutta). Four different incubation temperatures were used to control the maturation of the juveniles before zinc exposures. These 96-h exposures used flow-through conditions and four chronological ages of fish with weights ranging from 0.148 to 1.432 g. Time-to-death (TTD) data were collected throughout the exposure along with the final mortality. The results indicate that chronological age does not play a predictable role in zinc tolerance for juvenile brown trout. However, a relationship between zinc tolerance and fish size was observed in all chronological age populations, which prompted us to conduct additional exploratory data analysis to quantify how much of an effect size had during this stage of development. The smallest fish (0.148-0.423 g) were shown to be less sensitive than the largest fish (0.639-1.432 g) with LC50 values of 868 and 354 μg Zn/L, respectively. The Kaplan-Meier product estimation method was used to determine survival functions from the TTD data and supports the LC50 results with a greater median TTD for smaller fish than larger juvenile fish. These results indicate that fish size or a related characteristic may be a significant determinant of susceptibility and should be considered in acute zinc toxicity tests with specific attention paid to the expected exposure scenario in the field. © 2015 Springer Science+Business Media. Source


Iii H.C.,Michigan State University | Riley S.J.,Michigan State University | Winterstein S.R.,Michigan State University | Hiller T.L.,Michigan State University | And 3 more authors.
Wildlife Society Bulletin | Year: 2011

White-tailed deer (Odocoileus virginianus) create positive and negative effects incurred by stakeholders throughout the midwestern United States. Knowledge of deer ecology and stakeholder values for deer are needed to match the level of acceptable impacts with the capabilities of management. To address this challenge, we 1) quantified how landscape characteristics in southwestern and south-central Michigan, USA affect the distribution and population characteristics of deer throughout agro-forested landscapes, 2) quantified factors affecting stakeholder acceptance capacity for deer, and 3) present a deer management framework based on desired levels of impacts in relation to existing conditions. We investigated ecological components by radiocollaring deer during 2001-2006 and analyzed their movements, survival, and mortality factors in landscapes with diverse land-ownerships. Sociological components were investigated through interviews and questionnaires sent to 3,520 households. Southern Michigan residents identified a visible deer herd (a perceptual cue to the naturalness of the area) as a positive impact. Concerns about deer, especially deer-vehicle collisions, were weighed against positive impacts in determining acceptable levels of deerhuman interactions. Nonhunting, nonfarming rural residents, a stakeholder of increasing size and influence, perceived impacts distinct from those perceived by hunters and farmers. Small annual home ranges of yearlings-adults (77-202 ha) and fawns (60-116 ha) and high survival rates (yearling-adult = 0.40-0.94, fawns = 0.51-0.76) may be attributed to the parcelization of land, habitat quality, and positive values stakeholders hold for deer. Knowledge of the impacts perceived and the effect of impacts on acceptance capacity for deer may enable managers to develop management actions that complement existing programs and address stakeholder values. Knowledge of deer ecology, landscape characteristics, and responses of stakeholders to deer are critical for managing the impacts of white-tailed deer. © 2011 The Wildlife Society. Source


Walters D.M.,U.S. Geological Survey | Zuellig R.E.,U.S. Geological Survey | Crockett H.J.,Fort Collins Service Center | Bruce J.F.,U.S. Geological Survey | And 3 more authors.
Transactions of the American Fisheries Society | Year: 2014

Many native cyprinids are declining throughout the North American Great Plains. Some of these species require long reaches of contiguous, flowing riverine habitat for drifting eggs or larvae to develop, and their declining populations have been attributed to habitat fragmentation or barriers (e.g., dams, dewatered channels, and reservoirs) that restrict fish movement. Upstream dispersal is also needed to maintain populations of species with passively drifting eggs or larvae, and prior researchers have suggested that these fishes migrate upstream to spawn. To test this hypothesis, we conducted a mark-recapture study of Flathead Chub Platygobio gracilis within a 91-km reach of continuous riverine habitat in Fountain Creek, Colorado. We measured CPUE, spawning readiness (percent of Flathead Chub expressing milt), and fish movement relative to a channel-spanning dam. Multiple lines of evidence indicate that Flathead Chub migrate upstream to spawn during summer. The CPUE was much higher at the base of the dam than at downstream sites; the seasonal increases in CPUE at the dam closely tracked seasonal increases in spawning readiness, and marked fish moved upstream as far as 33 km during the spawning run. The upstream migration was effectively blocked by the dam. The CPUE of Flathead Chub was much lower upstream of the OHDD than at downstream sites, and <0.2% of fish marked at the dam were recaptured upstream. This study provides the first direct evidence of spawning migration for Flathead Chub and supports the general hypothesis that barriers limit adult dispersal of these and other plains fishes. Received March 12, 2013; accepted July 2, 2013. © 2014 Copyright Taylor and Francis Group, LLC. Source

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