Quantifying a potential mechanism between ice cover and cisco recruitment success: what role does light play in cisco embryonic development and larval survival?

Mark Vinson (USGS, mvinson@usgs.gov), Taylor Stewart (University of Vermont), Jason Stockwell (University of Vermont)

Over the past several decades, Coregonus recruitment has dwindled to unprecedented levels for unknown reasons. Coregonus species are fall spawners whose embryos incubate under ice throughout the winter and hatch in spring. Recent changes in ice cover coupled with poor Coregonus recruitment (ciscoes in particular) has led to speculation about the relationship between ice cover and embryo and larval survival for more than a decade with limited rectification. Potential mechanisms by which early ice cover might influence cisco recruitment success include the reduction of physical wave action, lower and more stable winter and spring water temperatures, and less light reaching the lake bottom. The objective of this project was to study Cisco from Lakes Superior and Ontario to experimentally measure how Cisco embryos respond to different ice regimes. We report on the effect of light on Cisco embryo development and the effect of incubation temperatures on Cisco larvae survival and growth. Our results have implications for Cisco propagation and for identifying a mechanism underlying poor Cisco recruitment.