Welcome to the interactive web schedule for the 2019 Midwest Fish & Wildlife Conference! Please note, this event has passed. To return to the main Conference website, go to: www.midwestfw.org.
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CONFERENCE SCHEDULE UPDATES & CHANGES: As a result of the prolonged government shutdown, we experienced a number of cancellations and changes to the schedule. Cancellations and changes are listed here (as of January 26, 2019).
AUTHORS: Andres Prada, University of Illinois at Urbana-Champaign; Amy George, Ben Stahlschmidt, Duane Chapman – USGS Columbia Environmental Research Center; Rafael O. Tinoco, University of Illinois at Urbana-Champaign
ABSTRACT: To monitor and control the spread of invasive fish species, such as grass carp (Ctenopharyngodon idella), we need to know where to find them. Natural streams have complex cross sections with varied bed roughness and in-stream obstructions that alter flow conditions and influence the transport of grass carp during its early life stages. To identify how changes in mean velocity, vorticity, and turbulence levels affect the drifting and swimming patterns of eggs and larval grass carp, we conducted a series of laboratory experiments in a recirculating flume. Live diploid grass carp eggs were stocked and monitored for 80 consecutive hours. We investigated three scenarios: 1) a gravel bump, 2) vertical rigid pier, and 3) rigid submerged vegetation. We used quantitative imaging to track eggs and larvae throughout the duration of each test, obtaining their preferred spatial distribution, as well as drifting and swimming trajectories under each flow scenario. We found clear correlations between the larval spatial distributions and flow conditions characterized through particle image velocimetry. Differences between identified trajectories for eggs and larvae at various developmental stages show a clear active response to spatially heterogeneous flow fields, where larvae actively avoided areas of high shear, preferring zones of lower turbulence and low vorticity levels. Data show that there is not only a threshold mean velocity which exceeds the swimming ability of the larvae, but also thresholds for turbulence statistics that define whether the eggs or larvae can be found at specific zones in natural streams. Since the three chosen scenarios generate turbulence and coherent flow structures at multiple scales at various orientations, our findings can be applied to inform detection and capture methods in natural streams.
