Browsing by Subject "Bythotrephes"
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Item Bythotrephes lake abundances and gear ensnarement abundances on Island Lake and Lake Mille Lacs, Minnesota, in 2017 and 2018(2022-07-14) Branstrator, Donn K; Brady, Valerie J; dbranstr@d.umn.edu; Branstrator, Donn K; University of Minnesota Duluth and NRRIThe repository contains two Excel data files, one based on samples collected from Island Lake Reservoir (Duluth MN) in 2017 (filename: IslandSpiny2017) and the other collected from Lake Mille Lacs (Garrison MN) in 2018 (filename: MilleLacsSpiny2018). Large portions of the analyzed data were first published in the referenced journal article. This article should be read for an overview of the locations where samples were collected and the nature of the data. Briefly, the data are measurements of the numbers and characteristics of spiny water flea (Bythotrephes) ensnared on various types of angling gear and the numbers and characteristics of spiny water flea collected by net tows at the locations and times that the angling gear types were deployed.Item 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 CenterInvasive 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.Item Hypoxia tolerance of the invasive zooplankton Bythotrephes longimanus and the native zooplankton Leptodora kindtii(2015-12) Sorensen, MichaelA predatory species of Eurasian zooplankton, Bythotrephes longimanus (spiny water flea), has been invading lakes and damaging food webs across the central part of North America since the early 1980s. In an effort to understand its niche, I investigated its short term survival under low dissolved oxygen (D.O.) concentrations in the laboratory and compared it to the native predatory zooplankton Leptodora kindtii. Both species are large-bodied, strongly selected by zooplanktivorous fish, and known to commonly engage in diel vertical migration. Trial conditions were chosen to mimic the hypolimnion of a eutrophic temperate zone lake during late summer. Tested B. longimanus (n=690) exhibited a pooled hypoxia tolerance limit (LC50) of 1.65 mg/L D.O. (95% confidence interval: 1.59, 1.72), while that of L. kindtii (n=380) was 0.58 mg/L D.O. (0.51, 0.65). Both species were more tolerant of hypoxia than zooplanktivorous fish, which cannot generally withstand prolonged exposure to D.O. concentrations lower than 2 mg/L. However, B. longimanus was significantly less tolerant than L. kindtii, and may exhibit greater spatial overlap with zooplanktivorous fish in seasonally-hypoxic lakes. These lab-based physiological results are consistent with landscape-scale observations that B. longimanus successfully invades primarily mesotrophic and oligotrophic lakes while L. kindtii thrives across a wider range of lakes, including eutrophic ones. The combined effects of climate change and cultural eutrophication throughout the 21st Century will likely increase the occurrence of temperate lake hypoxia, and provide a barrier to B. longimanus invasion of North American lakes.Item Long-Term Population Growth And Food Web Impacts Of The Spiny Water Flea (Bythotrephes Longimanus) Revealed From Sediment Records(2020-03) DeWeese, NicholeThe spiny water flea (Bythotrephes longimanus) is an invasive predacious zooplankton species that has well-documented impacts on aquatic food webs. However, few studies have examined long-term population dynamics and food web impacts of the species. This study used Bythotrephes subfossils, as well as subfossils from potential prey and competitor taxa (bosminids, daphniids, Simocephalus, and Leptodora kindtii) and pigment concentrations in 210Pb dated sediment cores from Mille Lacs Lake and Kabetogama Lake in Minnesota, USA to estimate first invasion and population growth of Bythotrephes and corresponding impacts on the lower food web. Bythotrephes evidence was found nearly 100 years prior to first detection in each lake, potentially making these lakes the earliest invaded lakes in North America. Bythotrephes subfossils slowly accumulated until around 1990, when accumulation rates rapidly increased. Two-piece linear models provided a good fit for Bythotrephes annual accumulation rates (a proxy for population size), and modelled lag phases lasted approximately 70 years in each lake. Of the native zooplankton species, Bosmina was the only species group that declined in correspondence with Bythotrephes population growth. Bosmina antennules and mucros were measured to analyze if morphological changes occurred as Bythotrephes populations grew, but these feature lengths did not consistently change over time. Sediment pigment concentrations did not increase with Bythotrephes population growth as expected in either lake. This research suggests that 1) Bythotrephes could be present in lakes decades before detection in zooplankton net samples, 2) populations take several decades to overcome lag phases, and 3) that other ecosystem factors may be more important than Bythotrephes in driving long-term food web changes in these lakes.