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Lake-wide, annual status in Mysis diluviana in Lake Michigan in 2015

Toby HoldaCBFS scientists Holda, Rudstam, and Watkins teamed up with NOAA fishery biologist Pothoven, USGS research fisheries biologist Warner, and National University of Life and Environmental Sciences of Ukraine professor Khyrstenko to investigate Lake Michigan Mysis diluviana population during 2015. Mysids are small 5 -20 mm long shrimp-like crustaceans that are both predators on smaller zooplankton and a major prey of fish in the Great Lakes. They migrate from the bottom into the water column at night and have to be sampled under red light as they avoid even low light levels but cannot perceive red light. The researchers were able to take a lake-wide, year-long, perspective the Lake Michigan Mysis population, looking at spatial and seasonal patterns in abundance and estimating annual life history rates. This paper presents the most detailed study of the mysid population in Lake Michigan since the 1970s. Mysids represented 10-13% of the total zooplankton biomass in the lake in 2015. Density and biomass were higher offshore as mysids prefer deep, cold water. Size structure analysis indicated generation times of 2 years making this animal the most long-lived zooplankton in the lake. More worrisome was that mysid production in Lake Michigan in 2015 was lower than most previous estimates in any of the Great Lakes. Lower annual secondary production by Mysis is a concern for fish managers as many of the important forage fish species feed heavily on Mysis. The paper “Lake-wide, annual status of the Mysis diluviana population in Lake Michigan in 2015” in the Journal of Great Lakes Research is available online for free download until Feb 11, 2021: Link: https://authors.elsevier.com/a/1cHq71MRgTf7sm