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CONFERENCE SCHEDULE UPDATES & CHANGES: As a result of the prolonged government shutdown, we experienced a number of cancellations and changes to the schedule. Cancellations and changes are listed here (as of January 26, 2019). 
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Tuesday, January 29 • 3:20pm - 3:40pm
(FISHERIES: INVASIVE SPECIES 2) Spawning Chronology and Environmental Factors Associated with Grass Carp Reproduction in the Sandusky River

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AUTHORS: Nicole R. King, University of Toledo Lake Erie Center; Madeline G. Tomczak, University of Toledo; Patrick M. Kocovsky, US Geological Survey; Christine M. Mayer, University of Toledo Lake Erie Center; Song S. Qian, University of Toledo Lake Erie Center

ABSTRACT: Invasive grass carp have been documented in the Great Lakes since 1975. Although occasional individuals have been captured, it was assumed that most were sterile escapees from stocked ponds. However, spawning was documented in the Great Lakes in 2015 with the collection of eight eggs from the Sandusky River, Ohio, a Lake Erie tributary. In 2016 no eggs were found despite extensive effort, likely because no high discharge events occurred, and grass carp, like some other non-native carps, spawn during high flows. Monitoring continued in 2017 with increased sampling effort including the addition of a second net and adaptive sampling after egg detection to follow the spatial extent of the egg mass. In 2017 the Sandusky River yielded 7,000+ eggs during two high flow events. The earliest developmental stage, three (stage one= no cell division, thirty= hatch) occurred at the most upstream site and the latest developmental stage (twenty five) near the river mouth. Egg stages were more variable at downstream sites and during lower flows; slower moving eggs are more likely to hatch in the river and survive to larvae. The pattern of egg stages and spatial distribution over time indicated spawning likely occurred several times or over a prolonged period. Although the hydrograph indicates that grass carp spawn during high flows, it is unknown what proximal cues initiate spawning and what specific conditions increase the likelihood of egg survival. We back calculated spawning time based on egg stage, collection location, and temperature to determine what specific factors may trigger spawning. Furthermore, we examined the conditions that likely support egg hatching and survival within the river. Preliminary analysis indicates several spawning bouts over a <10 hour time period. The ability to predict the timing and location of GC spawning and recruitment potential has implications for future control efforts.

Tuesday January 29, 2019 3:20pm - 3:40pm EST