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USGS - science for a changing world

Charles B. Yackulic

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Dams throughout western North America have altered thermal regimes in rivers, creating cold, clear “tailwaters” in which trout populations thrive. Ongoing drought in the region has led to highly publicized reductions in reservoir storage and raised concerns about potential reductions in downstream flows. Large changes in riverine thermal regimes may also occur as reservoir water levels drop, yet this potential impact has received far less attention. We analyzed historic water temperature and fish population data to anticipate how trout may respond to future changes in the magnitude and seasonality of river temperatures. We found that summer temperatures were inversely related to reservoir water level, with warm...
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These data were used to examine drivers behind changes in water temperature downriver of dams across the western U.S. from 1995-2015 and the influence of such changes on rainbow trout recruitment and rainbow and brown trout adult length. First, we linked reservoir storage capacity and dam size to the warmest monthly water temperature per water year (WY) to assess the influence of low storage capacity (shallow reservoirs) on downstream water temperature. We then took results from previously published Generalized Linear Mixed Models (GLMM) that assessed the influence of physical and biological predictors (e.g., flow, trout density, reservoir metrics) on trout recruitment and adult size and added mean annual, maximum...
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These data were used to examine the effectiveness of a non-lethal tool (Bioelectrical Impedance Analysis, "BIA") to estimate the physiological condition of endangered and threatened fishes in the Colorado River Basin. We conducted laboratory trials using hatchery-raised Humpback Chub and Bonytail and wild-captured Roundtail Chub, where fish were subjected to different feeding trials to elucidate a response in physiological condition and different temperature treatments to approximate field conditions. At the end of each 6-week trial fish were removed from tanks, lateral and dorsal measurements of BIA were taken, and fish were sacrificed for proximate composition analysis (lipid, protein, water, ash, dry mass, energy...
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1. Invertebrate drift is a fundamental process in streams and rivers. Studies from laboratory experiments and small streams have identified numerous extrinsic (e.g. discharge, light intensity, water quality) and intrinsic factors (invertebrate life stage, benthic density, behaviour) that govern invertebrate drift concentrations (# m−3), but the factors that govern invertebrate drift in larger rivers remain poorly understood. For example, while large increases or decreases in discharge can lead to large increases in invertebrate drift, the role of smaller, incremental changes in discharge is poorly described. In addition, while we might expect invertebrate drift concentrations to be proportional to benthic densities...
Categories: Publication; Types: Citation; Tags: Freshwater Biology
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This code was created to run a bioenergetics-based model of movement for Galapagos tortoises. It calculates energetic surplus or deficit at a daily time scale based on inputted temperature (6 times a day) and NDVI value (a single value per days), as well as the mass of an individual. It then uses dynamic programming to determine the optimal timing of movement between two foraging habitats, given time-series of NDVI in each habitat, and temperatures in both habitats and in a transition zone between habitats. The model relies on a variety of empirically derived relationships, including allometric relationships, derived for different groups of organisms (i.e., some relationships are based on analyses across multiples...
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