Predator-prey interactions in reservoirs
I conducted my M.S. Research, funded by the Ute Tribe Fish and Wildlife Department, with Dr. Phaedra Budy across an array of impoundments in northeast Utah in order to achieve a better understanding of predatory fish growth and performance.
Using a multifaceted approach of observation, field experimentation, and modeling, I addressed two primary objectives:
1) Quantify the effects of reservoir water level fluctuations on predator-prey interactions; and,
2) Determine factors limiting growth and performance of predators in Ute reservoirs
Using a multifaceted approach of observation, field experimentation, and modeling, I addressed two primary objectives:
1) Quantify the effects of reservoir water level fluctuations on predator-prey interactions; and,
2) Determine factors limiting growth and performance of predators in Ute reservoirs
Reservoir water level: linking visual foraging and prey densities
In reservoirs, seasonal drawdown can alter the physical environment and may influence predatory fish performance. We investigated the performance of lake trout Salvelinus namaycush in a western reservoir by coupling field measurements with visual foraging and bioenergetic models at four distinct states (early summer, mid-summer, late summer, and fall). The models suggested that trout prey, juvenile kokanee Oncorhynchus nerka, are limited seasonally by suitable temperature and dissolved oxygen. Accordingly, prey densities were greatest in late summer when reservoir volume was lowest and fish were concentrated by stratification. Prey encounter rates (up to 68 fish·day-1) and predator consumption are also predicted to be greatest during late summer. However, our models suggested that turbidity negatively correlates with prey detection and consumption across reservoir states. Under the most turbid conditions, lake trout did not meet physiological demands; however, during less turbid periods, consumption reached maximum bioenergetic efficiency. Overall our findings demonstrated that rapid reservoir fluctuations and associated abiotic conditions can influence predator-prey interactions, and our models described the potential impacts of water level fluctuation on valuable sport fishes.
Klobucar, S.L. and P. Budy. 2016. Consequences of seasonal variation in reservoir water level for predatory fishes: linking visual foraging and prey densities. Canadian Journal of Fisheries and Aquatic Sciences 73(1): 53 - 64.
Klobucar, S.L. and P. Budy. 2016. Consequences of seasonal variation in reservoir water level for predatory fishes: linking visual foraging and prey densities. Canadian Journal of Fisheries and Aquatic Sciences 73(1): 53 - 64.
Trying to push a square peg through a round hole: western waters stocking woes
In managed reservoirs, species interactions within novel fish assemblages can be difficult to predict and dependent on physical factors influenced by climatic change (e.g., temperature regimes and reservoir elevation). When numerous and novel suites of large-bodied fishes are stocked to meet angling desires, there is potential for competition among apex species. At both coarse and fine scales, we have been examining the interspecific interactions among piscivores in western reservoirs using a multifaceted approach (e.g., meta-analyses, stable isotopes, bioenergetics). We have documented an apparent mismatch between predators stocked, forage supply, and temperature regime.
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As a postgraduate researcher, I co-lead research funded by the Utah Division of Wildlife Resources, with Dr. Carl Saunders (Budy post-doc alum) and Dr. Phaedra Budy to better understand the success and potential impacts of introduced burbot (Lota lota) in Flaming Gorge Reservoir, a valuable sport fishery on the Wyoming/Utah border. Our two main objectives were:
1) Determine the potential food web impacts of burbot, specifically with regard to sport fish in Flaming Gorge Reservoir; and,
2) Investigate movement and life-history of burbot in Flaming Gorge Reservoir, to help determine potential control and/or removal strategies
media coverage: Salt Lake Tribune; KSL Outdoors
1) Determine the potential food web impacts of burbot, specifically with regard to sport fish in Flaming Gorge Reservoir; and,
2) Investigate movement and life-history of burbot in Flaming Gorge Reservoir, to help determine potential control and/or removal strategies
media coverage: Salt Lake Tribune; KSL Outdoors
A Lota lota consumption: trophic dynamics of nonnative burbot in a valuable sport fishery
While the native range of burbot is circumpolar, there are relatively few studies regarding the potential direct and indirect competitive interactions between burbot and popular sport fishes; even less is known about burbot as an invader. In their native range, adult burbot are generally described as piscivorous while juvenile burbot consume mostly macroinvertebrates, but these feeding habits likely vary seasonally. Additionally, burbot are long-lived, highly fecund, and mostly occupy coldwater habitats. These factors, along with their recent success within Flaming Gorge Reservoir (FGR), make burbot a threat to popular sport fish in FGR through direct and indirect competition for prey resources.
In this study, we investigated the spatial distribution and population status of burbot throughout FGR, and assessed the direct and indirect impacts of burbot on valued sport fish, especially trophy lake trout, in the reservoir. We sampled burbot and lake trout in distinct zones of FGR to assess the extent and stage of the invasion spatially. We collected diet and stable isotope samples, and extended our findings using a bioenergetics model, to quantify predation potential and competition. Collectively, we used these data to predict how this novel invader could affect the fishery into the future. Our findings provide critical information for management, especially if non-native burbot populations should continue to expand.
Klobucar, S.L., W.C. Saunders, and P. Budy. 2016. A Lota lota consumption: trophic dynamics of nonnative burbot in a valuable sport fishery. Transactions of the American Fisheries Society 145: 1386 - 1398.
Tracking and assessing spawning locations and early life history strategies of burbot in Flaming Gorge Reservoir, WY/UT
In their native range, burbot display a range of life histories, including lacustrian, adfluvial, and fluvial. However, across habitats, seasonal movements by burbot associated with spawning (December – February) can be extensive (> 50 km). Preliminary evidence from the Utah Division of Wildlife Resources and Wyoming Game and Fish Department suggested that exotic burbot inhabiting Flaming Gorge Reservoir may also travel long distances throughout the year. To understand the mechanisms driving the expansion of burbot throughout FGR, and thus their potential impacts on the reservoir, we determined the extent, timing, and destination of seasonal movements associated with winter spawning. We described heterogeneity among tagged burbot in movement patterns, identified and confirmed potential spawning locations, and described the timing of larval fish emergence.
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[cover photo: the fall inflow of Twin Pots Reservoir, UT-- this refill period drastically reduces water clarity, and water level rises rapidly]