Midwest Fish & Wildlife Conference 2019

AUTHORS: Rebecca A. Dillon, Aquatic Ecology Laboratory, Department of Evolution, Ecology, and Organismal Biology, The Ohio State University; Joseph D. Conroy, Inland Fisheries Research Unit, Division of Wildlife, Ohio Department of Natural Resources; Stuart A. Ludsin, Aquatic Ecology Laboratory, Department of Evolution, Ecology, and Organismal Biology, The Ohio State University

ABSTRACT: Hypolimnetic hypoxia has been shown to affect individual behavior, food web structure and interactions, and ecosystem function in aquatic ecosystems worldwide. While recent research has explored the impact of hypolimnetic hypoxia on coastal marine and large-lake food webs, less is known about the effects of hypoxia on reservoir food webs, especially pelagic ones. To address this gap, we examined how the spatial distribution of primary consumers (zooplankton) and secondary consumers (i.e., zooplanktivorous fish, clupeids; vertically migrating, hypoxia-tolerant, macroinvertebrates, Chaoborus spp.) varied between periods of normoxia (spring) and hypoxia (summer) in two small (surface area = 13.5, 11.7 km²), shallow (average depth = 6.6, 5.7 m) Ohio reservoirs. We tested the hypothesis that hypolimnetic hypoxia increases spatial overlap among zooplanktivorous fish, macroinvertebrates, and their potential zooplankton at night, whereas it reduces their overlap during the day because hypoxia-tolerant macroinvertebrates can use the hypoxic hypolimnion (and their zooplanktivorous fish predators cannot). We used net tows and hydroacoustics to describe the distribution and spatial overlap of zooplankton, Chaoborus, and zooplanktivorous fish during both day and night, and simultaneously measured physiochemical attributes (e.g., temperature, dissolved oxygen concentration, light levels). We found partial support for our hypothesis, as the overlap (determined from visual examination of net tow and hydroacoustics data) between fish and zooplankton was always high during periods with hypoxia, and was only high at night during normoxia. The overlap between Chaoborus and zooplankton was higher at night than during the day during periods of both normoxia and hypoxia, as Chaoborus were found at all depths during the day. Fish, Chaoborus, and zooplankton had the greatest spatial overlap at night during hypoxic periods. Our findings highlight the potential for hypoxia to alter pelagic food-web interactions in reservoir ecosystems.

AUTHORS: Richard R. Budnik, Ohio Department of Natural Resources, Division of Wildlife, Inland Fisheries Research Unit; Geoffrey B. Steinhart, The Ohio State University, Department of Evolution, Ecology and Organismal Biology, Aquatic Ecology Laboratory; Joseph D. Conroy, Ohio Department of Natural Resources, Division of Wildlife, Inland Fisheries Research Unit; Richard D. Zweifel, Ohio Department of Natural Resources, Division of Wildlife; Stuart A. Ludsin, The Ohio State University, Department of Evolution, Ecology and Organismal Biology, Aquatic Ecology Laboratory

ABSTRACT: Increased temperatures due to climate change will likely decrease the quality and quantity of habitat available to reservoir sport fish, although the extent of the effect will likely be variable by species. We developed bioenergetics models to estimate growth rate potential (GRP), a metric of habitat quality, for Largemouth Bass, saugeye, and White Crappie during a 13-year span (2005–2016) in three Ohio reservoirs that varied in productivity (summer 2012–2014 concentrations: chlorophyll a 7–55 µg/L; total phosphorus 21–106 µg/L). We contrasted these baseline measures of habitat quality with projected future changes in GRP and high-quality habitat (HQH; GRP > 0) availability under stabilizing (RCP 4.5) and increasing (RCP 8.5) carbon emission scenarios which estimate air temperatures will increase 2.5 and 4.8 degrees C by 2099. Our simulations predicted Largemouth Bass, saugeye, and White Crappie GRP would decrease an average of 0.001 g/g/day, 0.003 g/g/day, and 0.007 g/g/day, respectively, under RCP 4.5, and 0.005 g/g/day, 0.004 g/g/day, and 0.013 g/g/day under RCP 8.5. The average reduction of HQH was greatest for saugeye (20% loss) under RCP 4.5 and for White Crappie (45% loss) under RCP 8.5. Largemouth Bass HQH was the least affected with an average reduction of < 9% under both scenarios in all reservoirs. Temperature increases in the highest productivity reservoir led to the greatest reduction in habitat quality and quantity among reservoirs. These outcomes, as shaped by temperature changes, have the potential to influence not only the performance of individual fish but also will affect population dynamics, trophic interactions, and fish community structure.

AUTHORS: Eric J. Gates, University of Illinois Urbana-Champaign; Anthony Porreca, Illinois Natural History Survey; Joseph Parkos III, Illinois Natural History Survey; David H. Wahl, University of Illinois Urbana-Champaign.

ABSTRACT: Lentic ecosystems are negatively affected by habitat degradation due to reservoir senescence and riparian zone development. The addition of coarse woody habitat (CWH) and artificial habitat (e.g., plastic fish attractors) is a popular management strategy used to enhance systems that have experienced declines in habitat availability. However, the mechanisms by which CWH and artificial habitat additions influence aquatic food webs remain understudied. We introduced either artificial habitat structures or CWH (Quercus alba) into ten 0.04-ha experimental ponds to test whether macroinvertebrate communities and largemouth bass growth differed between introduced habitats. The experiment ran for three months and structures were allowed to condition for one month prior to stocking juvenile largemouth bass. Macroinvertebrate communities were similar between habitat types. However, more taxa were found on the artificial structures and macroinvertebrate communities colonizing CWH appeared to increase relative to artificial habitat by the end of experiment. Largemouth bass growth did not differ between CWH and artificial habitat. Although not specifically tested, macroinvertebrate communities appeared to be influenced by the presence and amount of periphyton colonizing habitat structures. Our results indicate that habitat material itself was not as important as providing a stable substrate for primary production and subsequent macroinvertebrate colonization. Longer experiments may be necessary to determine the maximum influence of these habitats on primary and secondary productivity, particularly as CWH conditions.

AUTHORS: Elisa Baebler, Missouri Cooperative Fish and Wildlife Research Unit, The School of Natural Resources, University of Missouri; Craig Paukert, U.S. Geological Survey, Missouri Cooperative Fish and Wildlife Research Unit, The School of Natural Resources, University of Missouri

ABSTRACT: Downstream of hydropeaking dams, water depth and velocity fluctuate rapidly, which leads to short-term changes in physical habitat supporting aquatic organisms. While some fish species have been extirpated from flow-regulated systems, other species flourish, which may be related to the persistence of critical habitats complementary to these life histories. We used radio telemetry to evaluate the influence of season and streamflow on the habitat selection of two common, native fishes downstream of Bagnell Dam in central Missouri from April 2016 to June 2017. We studied Spotted Bass (Micropterus punctulatus), nest-guarding, sight feeding, habitat generalists and Shorthead Redhorse (Moxostoma macrolepidotum), fluvial dependent, migratory, benthic feeders. Spotted Bass selected moderate depths near submerged cover in all seasons and slow velocities during spring and summer. Conversely, Shorthead Redhorse preferred moderately deep and faster flowing habitats during spring and summer and used slow velocities and shallow depths during winter. Spotted Bass and Shorthead Redhorse selected velocity, depth, submerged cover, and distance to shore during stable and/or fluctuating flows, suggesting that fish may respond to streamflow over short time periods (daily). Spotted Bass used slow velocities (less than 0.4 m/s) in both fluctuating and stable flows, whereas, Shorthead Redhorse preferred fast velocities (greater than 1.0 m/s) in stable flows but did not select velocity during fluctuating flows. Shorthead Redhorse and Spotted Bass habitat selection illustrates that even native fish that prosper in regulated rivers have habitat requirements which may be better met through managing flow releases to maintain river habitats that support native fish of multiple guilds.

AUTHORS: Kathryn Renik, Dr. Andrew Hafs, Dr. Jeffrey Ueland – Bemidji State University

ABSTRACT: Developments in geographic information systems (GIS) and improved global positioning system (GPS) unit accuracy have allowed for advancement and are increasingly being used to collect spatial data in ecological studies. Benefits include decreased error in the field and ease of usability, allowing for quicker and more accurate field measurements. The objective of this study was to quantify the accuracy of predicted Brook Trout Salvelinus fontinalis habitat from spatially interpolated GIS maps generated using a Trimble Geo7x handheld GPS unit. Brook Trout habitat variables were collected at data points throughout 40 (200m) stream reaches during summer 2018 in Northeastern Minnesota. Data was recorded directly onto the Geo7x GPS unit and two different data point types were collected, data points for creating interpolated habitat maps (“map data points”) and reference data points.  A habitat suitability index model was utilized to predict Brook Trout habitat and produce spatially interpolated GIS maps by kriging. Quantification of interpolated map accuracy was determined by comparing the interpolated values to the reference data points. An error matrix was used to calculate overall accuracy, user’s accuracy, producer’s accuracy, and the kappa coefficient, allowing us to determine the ability of interpolated maps to accurately predict Brook Trout habitat. Accurate Brook Trout habitat maps provide management not only with tools to successfully manage the species, but also with illustrative visual aides that allow for improved communication within agencies and among the public.