Testing diel vertical migration cues in fish and Mysis with surface drones in Lake Superior

Numerous organisms participate in diel vertical migrations (DVM) in pelagic waters in lakes and oceans. In the Laurentian Great Lakes, the omnivorous crustacean Mysis diluviana (hereafter Mysis) are a key food web component and prey item for fish. Mysis migrate upwards at night to feed on other plankton and then retreat to deeper water at day with predatory fish paralleling these movements. Studying this DVM cycle in the Great Lakes has often been limited either temporally or spatially because of logistical challenges. However, high endurance surface drones are now available that allow DVM patterns to be studied over large spatial and temporal scales. We deployed two uncrewed surface vessels equipped with 120 kHz Simrad EK80 transducers in western Lake Superior from August to September of 2022 to measure fish and Mysis vertical distributions in the water column. We utilized existing laboratory-derived mechanistic models of Mysis preferred depth to predict their location within the water column across the sampling period and compared this to in situ distributions observed in Lake Superior to understand drivers of this species’ diel migrations. Mysis were highly responsive to light (even changes in moonlight), choosing to descend as light levels rose. Further, we observed that Mysis generally remained suspended above the bottom of the lake, weakening benthic-pelagic coupling by these organisms. Fish were often found under the Mysis during the night, and amongst the Mysis during the day. The use of autonomous drones equipped with acoustics instrumentation facilitates fish and Mysis observations across large spatial scales and opens new opportunities to answer questions about the ecological role of vertical migrations in lake food webs.

Presentation Preference: Oral

Primary Presenter: Thomas Evans, Cornell University (tme33@cornell.edu)

Authors:

Kayden Nasworthy, Cornell University  (kcn33@cornell.edu)

Lars Rudstam, Cornell University  (lgr1@cornell.edu)

Suresh Sethi, Brooklyn College  (suresh.sethi@brooklyn.cuny.edu)

Daniel Yule, U.S. Geological Survey, Great Lakes Science Center, Lake Superior Biological Station  (dyule@usgs.gov)

Hannah Blair, Cornell University  (hbb59@cornell.edu)

James Watkins, Cornell University  (jmw237@cornell.edu)

Peter Esselman, U.S. Geological Survey Great Lakes Science Center  (pesselman@usgs.gov)