Movements and habitat use of cisco along a nearshore-offshore gradient in northern Lake Huron

Christopher Holbrook (USGS, cholbrook@usgs.gov), Todd Hayden (USGS), David Fielder (Michigan DNR), Kevin McDonnell (USFWS), Thomas Binder (USGS), Aaron Fisk (University of Windsor)

Historically, the Great Lakes supported large and diverse cisco populations until overfishing, establishment of invasive species, and habitat loss resulted in large-scale extirpation during the mid 19th century.  Managers have prioritized recovery of cisco in Lake Huron and implemented a restoration stocking program with the goal to reestablish naturally spawning populations in Saginaw Bay using gametes collected from cisco spawning aggregations in the Les Cheneaux Islands.  Understanding the movement ecology and habitat preferences of cisco in the Les Cheneaux Islands are important for identifying stocking locations and prioritizing habitat restoration efforts.  We report results from our study to track cisco movements and habitat occupancy on a large acoustic receiver array encompassing a nearshore-offshore gradient in northern Lake Huron. Our results suggest cisco occupy areas within the Les Cheneaux Islands and nearshore Lake Huron during winter and spring but habitat use expanded during the summer and early fall to include offshore regions of Lake Huron.  A model of habitat occupancy trained on observed cisco presence and absence from acoustic telemetry and combined with a suite of environmental and spatio-temporal features predicted that cisco generally occupied habitats within 3 km of shore and within 30 km of the Les Cheneaux Islands where they were tagged during spawning. Distance from release location, water temperature and time of year were the most important features for predicting cisco presence in northern Lake Huron. Depth experienced by cisco was consistent among seasons (~20 m) and movement patterns were repeated over multiple years. Our results suggested that the Les Cheneaux Islands cisco population does not undertake basin-wide movements, but is strongly associated with the complex shoreline habitat characterized by bays and channels around the Les Cheneaux Islands and the northern shore of Lake Huron.