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SFS Annual Meeting

Thursday, May 23, 2019
09:00 - 10:30

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09:00 - 09:15: / 250 DE BOTTOM-UP EFFECTS OF LAKE TROUT SUPPRESSION IN YELLOWSTONE LAKE

5/23/2019  |   09:00 - 09:15   |  250 DE

BOTTOM-UP EFFECTS OF LAKE TROUT SUPPRESSION IN YELLOWSTONE LAKE Lake Trout (Salvelinus namaycush) were introduced into Yellowstone Lake, Wyoming causing a 90% decline in the native Yellowstone Cutthroat Trout (Oncorhynchus clarkii bouvieri) population. In addition to gillnetting, the National Park Service investigated alternative suppression to target the embryos of Lake Trout, including depositing Lake Trout carcasses on spawning sites causing embryo mortality from low dissolved oxygen concentrations, but the effects on nutrient cycling and the foodweb are unknown. We analyzed water samples for nutrients, algae and invertebrates for 15N, and measured ammonium uptake rate by algae throughout the open water season to investigate the degree to which carcasses altered nutrient cycling and these nutrients moved through the foodweb. Ammonium concentrations were 4x higher compared to previous data indicating mineralization of carcasses. Chlorophyll a concentrations increased following carcass deposition indicating increased algae biomass. Isotope samples are currently being analyzed. We expect that 15N from carcasses will be incorporated into algae and invertebrates quickly. Additionally, we predict phytoplankton and periphyton will take up more nitrogen after carcasses were deposited. Understanding how carcass deposition alters the foodweb will help managers understand the effectiveness of alternative suppression and subsequent effects on the ecosystem.

Lusha Tronstad (Co-Presenter/Co-Author), University of Wyoming, Wyoming Natural Diversity Database, tronstad@uwyo.edu;


Todd Koel (Co-Presenter/Co-Author), Yellowstone National Park, todd_koel@nps.gov;


Michelle Briggs (Co-Presenter/Co-Author), Montana State University, michelle.briggs32@gmail.com;


Lindsey Albertson (Co-Presenter/Co-Author), Montana State University , lindsey.albertson@montana.edu;


Hayley Glassic (Co-Presenter/Co-Author), Montana Cooperative Fishery Research Unit, hcg0509@gmail.com;


Christopher Guy (Co-Presenter/Co-Author), U.S. Geological Survey, Montana Cooperative Fishery Research Unit, Montana State University, cguy@montana.edu;


Dominique Lujan (Primary Presenter/Author), University of Wyoming, dlujan1@uwyo.edu;


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09:15 - 09:30: / 250 DE DO OMNIVORES MEDIATE THE EFFECTS OF DEGRADATION?

5/23/2019  |   09:15 - 09:30   |  250 DE

DO OMNIVORES MEDIATE THE EFFECTS OF DEGRADATION? Anthropogenic activities have led to habitat degradation in streams throughout much of North America. In particular, cattle grazing has caused a loss of riparian vegetation resulting in higher water temperatures and an increase in nutrient runoff. The effects of habitat degradation on food quality and quantity for aquatic consumers could have large implications for stream communities. Since omnivores feed at multiple trophic levels, they increase community complexity and may increase the resistance and resilience of altered communities. To test the hypothesis that omnivores positively impact community stability in degraded habitats, I established mesocosms using 1000L cattle tanks with two disturbance factors: decrease in shade mimicking a degraded riparian zone and an increase in nutrients representing cattle inputs, and the presence or absence of the omnivorous speckled dace (Rhinichthys osculus). Stability was determined by analyzing differences in invertebrate, zooplankton, and algal biomass across treatments. By understanding the role omnivory plays in degraded aquatic systems, we can gain insight into both the management and restoration of these ubiquitous habitats.

Hannah Moore (Primary Presenter/Author), Murray State University, hmoore17@murraystate.edu;


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09:30 - 09:45: / 250 DE CHARACTERIZING LIMNOLOGICAL PARAMETERS IN KANSAS SMALL IMPOUNDMENTS ACROSS A GRADIENT OF GIZZARD SHAD DENSITIES

5/23/2019  |   09:30 - 09:45   |  250 DE

CHARACTERIZING LIMNOLOGICAL PARAMETERS IN KANSAS SMALL IMPOUNDMENTS ACROSS A GRADIENT OF GIZZARD SHAD DENSITIES Gizzard shad (Dorosoma cepedianum) are important prey for sportfish in small impoundments. However, overabundant shad create problems by depleting zooplankton and translocating nutrients from benthic detritus into the water column, compounding eutrophication. Understanding how gizzard shad regulate pelagic food webs in small impoundments may aid managers in anticipating and managing water quality issues stemming from extrinsic nutrient input. As a baseline for a gizzard shad eradication project, we compared a suite of limnological parameters across a gradient of shad densities. We anticipated high primary productivity and zooplankton communities dominated by rotifers and copepods in impoundments with high shad densities. Shad densities in 12 impoundments were estimated from standardized fall gill-net sampling between 2015-2018. Compartments of the pelagic food web in these impoundments were also sampled in June, August, and October 2017 and 2018. Spearman’s rank correlation indicated no association between shad density (gill-net CPE) and nutrient concentrations, chlorophyll a or Secchi depth, but cladoceran densities were negatively correlated with higher shad densities (? = -0.18, p = 0.013). A high degree of among-impoundment variation in environmental factors might have limited our ability to detect a relationship with shad abundance.

Elizabeth Renner (Primary Presenter/Author), Kansas State University, earenner@ksu.edu;


Keith Gido (Co-Presenter/Co-Author), Kansas State University, kgido@ksu.edu;


Ben Neely (Co-Presenter/Co-Author), Kansas Department of Wildlife, Parks and Tourism, ben.neely@ks.gov;


Jeff Koch (Co-Presenter/Co-Author), Kansas Department of Wildlife, Parks and Tourism, jeff.koch@ks.gov;


Connor Chance-Ossowski (Co-Presenter/Co-Author), Kansas Department of Wildlife, Parks and Tourism, connor.ossowski@ks.gov;


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09:45 - 10:00: / 250 DE FISHERIES FOOD WEB EFFECTS OF ZEBRA MUSSELS AND SPINY WATER FLEA IN LARGE NORTH TEMPERATE LAKES

5/23/2019  |   09:45 - 10:00   |  250 DE

FISHERIES FOOD WEB EFFECTS OF ZEBRA MUSSELS AND SPINY WATER FLEA IN LARGE NORTH TEMPERATE LAKES Zebra mussels Dreissena polymorpha (ZM) and spiny water flea Bythotrephes longimanus (SWF) are non-native aquatic invasive species (AIS) in North America. Both species can dramatically alter zooplankton biomass, phytoplankton communities, and water clarity; however, how these impacts transmit to higher levels of the food web is not well understood. We compared trophic position and percent littoral versus pelagic resource contribution to age-0 and adult sport fish across nine large (> 6,400 ha) Minnesota lakes at various stages of invasion by ZM and SWF. We also quantified changes in growth of age-0 walleye, Sander vitreus, and yellow perch, Perca flavescens, using historical data. We found substantial variation in the percent littoral resource contribution to fish across lakes which followed patterns of invasion status. Walleye and yellow perch in invaded lakes relied more heavily on pelagic resources, despite reductions in pelagic plankton biomass. Furthermore, age-0 walleye grew more slowly and were on average 14 and 12% smaller at the end of the growing season when ZM and SWF were present, respectively. These findings suggest that continued reliance on pelagic energy resources following AIS establishment may have negative consequences for sport fish.

Gretchen Hansen (Co-Presenter/Co-Author), University of Minnesota, ghansen@umn.edu;


Tyler Ahrenstorff (Co-Presenter/Co-Author), Minnesota Department of Natural Resources, tyler.ahrenstorff@state.mn.us;


Heidi Rantala (Co-Presenter/Co-Author), Minnesota Department of Natural Resources, heidi.rantala@state.mn.us;


Valerie Brady (Co-Presenter/Co-Author), Natural Resources Research Institute, University Minnesota Duluth, vbrady@d.umn.edu;


Josh Dumke (Co-Presenter/Co-Author), Natural Resources Research Institute, University of Minnesota, jddumke@d.umn.edu;


Will French (Co-Presenter/Co-Author), Minnesota Department of Natural Resources, will.french@state.mn.us;


Jodie Hirsch (Co-Presenter/Co-Author), Minnesota Department of Natural Resources, jodie.hirsch@state.mn.us;


Katya Kovalenko (Co-Presenter/Co-Author), Natural Resources Research Institute, Univ. Minnesota Duluth, philarctus@gmail.com;


Ryan Maki (Co-Presenter/Co-Author), Voyageurs National Park, ryan_maki@nps.gov;


Bethany Bethke (Primary Presenter/Author), Minnesota Department of Natural Resources, bethany.bethke@state.mn.us;


Holly Wellard Kelly (Co-Presenter/Co-Author), University of Minnesota-Duluth NRRI, hwellard@d.umn.edu;


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10:00 - 10:15: / 250 DE USING PROXY DATA TO INFER PREDATOR PREY INTERACTIONS IN STREAM

5/23/2019  |   10:00 - 10:15   |  250 DE

USING PROXY DATA TO INFER PREDATOR PREY INTERACTIONS IN STREAM Food webs are a powerful way to represent the diversity, structure, and function of ecological systems. However, the accurate description of food web structure requires significant allocation of time and resources, limiting their widespread use in ecological studies. However, methods exist for the inference of feeding interactions using proxy variables. Here, we predict the presence of trophic interactions between species based on population-level data (e.g. body size and local abundance), and compare our results to known food web structure. We show that this model performs well at predicting individual species interactions, and that these individual predictions scale up to the network level, resulting in food web structure of inferred networks being similar to their empirical counterparts. Our results indicate that inferring food web structure using proxy variables can be an efficient way of estimating food web structure. The model presented here can facilitate the investigation of variation in food web structure across spatiotemporal and environmental gradients, and can aid in our understanding of the mechanisms leading to predator-prey interactions.

Justin Pomeranz (Primary Presenter/Author), University Canterbury, jfpomeranz@gmail.com;


Ross Thompson (Co-Presenter/Co-Author), University of Canberra, ross.thompson@canberra.edu.au;


Timothée Poisot (Co-Presenter/Co-Author), University of Montreal, timothee.poisot@umontreal.ca;


Jon Harding (Co-Presenter/Co-Author), University Canterbury, jon.harding@canterbry.ac.nz;


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