Browsing by Author "Hansen, Gretchen J A"

Now showing 1 - 5 of 5
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    Data and R code for analysis of walleye and yellow perch age-0 length in Minnesota's Large Lakes
    (2019-12-10) Hansen, Gretchen J A; Bethke, Bethany J; Ahrenstorff, Tyler D; Dumke, Josh; Hirsch, Jodie; Kovalenko, Katya E; LeDuc, Jaime F; Maki, Ryan P; Rantala, Heidi M; ghansen@umn.edu; Hansen, Gretchen; Minnesota Aquatic Invasive Species Research Center (MAISRC)
    Invasive species represent a threat to aquatic ecosystems globally; however, impacts can be heterogenous across systems. Documented impacts of invasive zebra mussels (Dreissena polymorpha) and spiny water fleas (Bythotrephes cedarstroemi; hereafter Bythotrephes) on native fishes are variable and context dependent across locations and time periods. Here, we use a hierarchical Bayesian analysis of a 35-year dataset on two fish species from 9 lakes to demonstrate that early life growth of ecologically important fishes are influenced by these aquatic invasive species. Walleye (Sander vitreus) grew more slowly throughout their first year of life, and were on average 12 or 14% smaller at the end of their first summer following invasion by Bythotrephes or zebra mussels, respectively. Yellow perch (Perca flavescens) growth was less affected by invasion. Yellow perch on average grew more slowly in their first year of life following invasion by zebra mussels, although this effect was not statistically distinguishable from zero. Early life growth of both walleye and yellow perch was less tightly coupled to degree days in invaded systems, as demonstrated by increased variance surrounding the degree day-length relationship. Smaller first-year size is related to walleye survival and recruitment to later life stages and has important implications for lake food webs and fisheries management. Future research quantifying effects of zebra mussels and Bythotrephes on other population-level processes and across a wider gradient of lake types is needed to understand the mechanisms driving observed changes in walleye growth.
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    Data and R code supporting “Non-linear water clarity trends and impacts on littoral area in Minnesota lakes”
    (2021-04-19) Vitense, Kelsey; Hansen, Gretchen J A; viten003@umn.edu; Vitense, Kelsey; University of Minnesota Fisheries Systems Ecology Lab
    This repository contains the data and R code used to conduct the analyses in the article "Non-linear water clarity trends and impacts on littoral area in Minnesota lakes" in Limnology and Oceanography Letters.
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    Data in support of Connecting habitat to species abundance: the role of light and temperature in the abundance of walleye in lakes
    (2022-01-25) Mahlum, Shad; Vitense, Kelsey; Corson-Dorsch, Hayley; Platt, Lindsay; Read, Jordan; Schmalz, Patrick; Treml, Melissa; Hansen, Gretchen J A; smahlum@umn.edu; Mahlum, Shad; Department of Fish, Wildlife, and Conservation Biology
    This repository contains the data used to conduct the analyses in the article " Connecting habitat to species abundance: the role of light and temperature in the abundance of walleye in lakes.”
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    Data in Support of Predicting climate change impacts on poikilotherms using physiologically guided species abundance models
    (2022-07-14) Schliep, Erin M; North, Joshua S; Kundel, Holly; Custer, Christopher A; Ruzich, Jenna K; Hansen, Gretchen J A; ghansen@umn.edu; Hansen, Gretchen J A; University of Minnesota Dr. Hansen Research Team
    Fish catch and effort data for three species caught in gill nets and trap nets between 1988 and 2019 as part of Minnesota Department of Natural Resources (MNDNR) fisheries surveys conducted during the summer and early fall are included from over 1,300 Minnesota lakes. The three fish species included are: bluegill (Lepomis marochirus) a warm-water adapted species, yellow perch (Perca flavescens) a cool-water adapted species, and cisco (Coregonus artedi) a cold-water adapted species. Additional data concerning lake characteristics and surrounding land cover were also included. Mean July lake surface temperature was calculated using simulated daily water temperatures. Watershed land use including agricultural, barren, forest, grass, shrub, urban, and wetland cover, was determined using the 2016 National Land Cover Database. Secchi, a measure of water clarity was calculated from remotely sensed Secchi depth courtesy of Max Glines. Lastly, lake area and maximum depth were obtained from MNDNR public databases.
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    Data in Support of Widespread declines in walleye recruitment following zebra mussel invasion in Minnesota lakes
    (2023-04-26) Kundel, H; Hansen, Gretchen J A; kunde058@umn.edu; Kundel, H; University of Minnesota Dr. Hansen Research Team
    Invasive zebra mussels (Dreissena polymorpha) alter lake ecosystems and can negatively affect first-year growth of walleye (Sander vitreus), potentially lowering walleye overwinter survival and recruitment success. Zebra mussel effects also vary among lakes, and walleye resilience to the effects of zebra mussels may vary depending on lake characteristics (e.g., depth, clarity) or fish community composition. To test these hypotheses, we used data from 1,438 surveys across 348 lakes collected between 1993 and 2019 to measure walleye recruitment, defined as relative abundance of age-0 walleye in their first fall. We fitted Bayesian hierarchical models to quantify the effects of zebra mussels on walleye recruitment while accounting for the effects of lake temperature, surface area, and water clarity. A before-after-control-impact (BACI)-like design was used to account for potential changes in recruitment due to factors other than zebra mussel invasion. Age-0 walleye recruitment to their first fall was ~41% lower (95% credible interval of 38 - 44%) in lakes containing zebra mussels compared to uninvaded lakes. Invaded lakes had higher recruitment prior to zebra mussel invasion than lakes that remain uninvaded. Conversely, walleye recruitment increased slightly (7% (95% credible interval 2 - 11%)) in lakes without zebra mussels over the same time period. Walleye recruitment was higher in larger lakes and lakes with lower water clarity. Water temperature, as indexed by degree days (base 5 °C), did not affect walleye recruitment. Our results demonstrate negative effects of zebra mussel invasion on walleye population dynamics at a landscape scale.