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Mysis ecology in the Great Lakes

Jim Watkins, Lars Rudstam, Toby Holda, Patrick Boynton, Taylor Herne (Cornell University), Brian O’Malley, Dave Warner (USGS), Steve Pothoven (NOAA-GLERL), Kelly Bowen, Warren Currie (DFO Canada), Rosaura Chapina, Jason Stockwell (University of Vermont), David Jude (University of Michigan), Dmytro Khrystenko (National University of Life and Environmental Sciences of Ukraine), Alexander Karatayev, Lyubov Burlakova (Buffalo State College), Sture Hansson (Univ Stockholm, Sweden , Steve Chipps (South Dakota State). Funded by: US EPA GLNPO and GLFC

Mysids are an important native species in all the Great Lakes as well as other inland lakes. Understanding mysid ecology is an essential component of understanding these systems as the species is both a major predator on zooplankton and a major prey for alewife, smelt and native coregonids. Historic declines in mysids, changing prey-fish communities, and oligotrophication in the Great Lakes have caused scientists to question the long-term reliability of mysids as a food source and to further investigate population dynamics and drivers of change.  In 2021, we published a manuscript on Michigan mysids from the CSMI year of 2015 (Holda et al. 2021) and are working on a manuscript documenting historic and recent (1997-2019) trends in mysid abundance and recent life history across all five lakes.

Diel vertical migration (DVM) is an important component of food web interactions and population assessments in the Great Lakes. Mysis is assumed to undergo DVM and migrate into the pelagia at night. Consequently, Mysis assessment protocols rely on nocturnal pelagic sampling. Mysis, however, exhibit partial DVM (PDVM) – Mysis have been observed on the bottom at night in lakes Ontario, Superior, and elsewhere. The proportion of Mysis populations which exhibit PDVM is unknown, as are the factors which cause some individuals to remain benthic at night. Recent data from Lake Champlain challenge conventional assumptions about Mysis DVM – a substantial portion of the population does not migrate and is thus unavailable to pelagic gear. In 2020 we surveyed mysids with both a dropdown camera and mysid nets both day and night in Lake Michigan. We will also continue this research in lakes Huron, Superior, and Ontario in 2022-2023.  If the night benthic component of Mysis populations is high, then a re-evaluation of profundal food web structure/function and outcomes of management actions would be necessary to include more realistic estimates of Mysis biomass and distribution. Moreover, if PDVM is related to seasonal patterns in reproductive status, energy reserves, body sizes or environmental conditions, then sampling protocols can be modified to account for these drivers of Mysis behavior when determining lake-wide biomass estimates. An analysis of the energetics costs of migration was completed using data from western US (Chipps et al. 2022).