Lars G. Rudstam
Steven A. Pothoven
David Warner
Dmytro S. Krystenko
James M. Watkins
Toby J. Holda
2021
<p><i>Mysis diluviana</i><span> is one of the most abundant zooplankton by biomass in the Laurentian Great Lakes of North America, a predator of other zooplankton and an important prey for fishes. Studies of long-term trends in Lake Michigan have shown 2005–2016 densities to be 50–80% lower than 1990s densities, but these observations have been based on annual monitoring that is either spatially or seasonally limited. We combined Lake Michigan </span><i>Mysis</i><span> data from three annual programs and the 2015 Cooperative Science and Monitoring Initiative to achieve broad spatial coverage during spring, summer, and fall of 2015 and broad depth coverage during spring 2016. Lake-wide, annual density and biomass were 82 (SE: 10) </span><i>Mysis</i><span>/m</span><sup>2</sup><span> and 200 (SE: 36) mg dry mass/m</span><sup>2</sup><span>. Density and biomass estimates were highest offshore, generally higher in the north basin, and seasonally highest in summer. Annual lake-wide averages for depths >30 m were better captured by seasonally-extensive annual programs than spatially-extensive annual programs, although spring sampling may bias annual values low. </span><i>Mysis</i><span> cohorts grew 0.026 mm/d (age-0) and 0.007 to 0.027 mm/d (age-1). Annual mortality was 81–98%. Reproduction was fall-spring and seasonal lake-wide estimates ranged from 0.6 to 19.1% females brooding, 13–20 embryos/brood, and 3–46 embryos/m</span><sup>2</sup><span>. Annual production (423 mg dry mass/m</span><sup>2</sup><span>/yr, SE: 31) was lower than all but one previous estimate from lakes Michigan, Huron, and Ontario. While </span><i>Mysis</i><span> tend to persist, low </span><i>Mysis</i><span> production may be a concern for prey fishes that feed on </span><i>Mysis</i><span>.</span></p>
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10.1016/j.jglr.2020.11.012
en
Elsevier
Lake-wide annual status of Mysis diluviana population in Lake Michigan in 2015
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