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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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Background Characterizing the movement patterns of animals is an important step in understanding their ecology. Various methods have been developed for classifying animal movement at both coarse (e.g., migratory vs. sedentary behavior) and fine (e.g., resting vs. foraging) scales. A popular approach for classifying movements at coarse resolutions involves fitting time series of net-squared displacement (NSD) to models representing different conceptualizations of coarse movement strategies (i.e., migration, nomadism, sedentarism, etc.). However, the performance of this method in classifying actual (as opposed to simulated) animal movements has been mixed. Here, we develop a more flexible method that uses the same...
Categories: Publication; Types: Citation; Tags: Movement Ecology
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1. The reasons that lead some animals to seasonally migrate, and others to remain in the same area year-round, are poorly understood. Associations between traits, such as body size, and migration provide clues. For example, larger species and individuals are more likely to migrate.2. One explanation for this size bias in migration is that larger animals are capable of moving faster (movement hypothesis). However, body size is linked to many other biological processes. For instance, the energetic balances of larger animals are generally more sensitive to variation in food density because of body size effects on foraging and metabolism and this sensitivity could drive migratory decisions (forage hypothesis).3. Identifying...
Categories: Publication; Types: Citation; Tags: Journal of Animal Ecology
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