How many cisco should be stocked, and at what life stage?

Contributing Authors

Benjamin Rook (USGS,, Michael Hansen (USGS), Charles Bronte (USFWS)

Executive Summary

Historically, members of the coregonine complex (Coregonus spp.) were the most abundant and ecologically important fish species in the Great Lakes (especially the cisco C. artedi), but anthropogenic influences caused nearly all populations to collapse by the 1970s. Managers have begun exploring the feasibility of reintroducing and restoring populations throughout the basin, but questions regarding hatchery propagation and stocking must be addressed before large-scale restoration can proceed. We used historical and contemporary stock-recruit parameters previously estimated for ciscoes in Wisconsin waters of Lake Superior, with estimates of suitable rearing habitat area and natural mortality, to estimate how many fry, fall fingerling, and age-1 hatchery fish are needed for cisco stocking in the Great Lakes. Estimated stocking densities were similar to those for related European Coregonus species and suggest that basin-wide stocking will require at least 1.0-billion fry, 766-million fall fingerlings, or 563-million age-1 fish. Because our results suggest that basin-wide stocking will require numbers of fish considerably greater than current or planned production capacity, simultaneous stocking throughout the Great Lakes is not feasible at present. To maximize effectiveness of available production capacity, available resources could be concentrated on critical cisco spawning areas, such as (1) Saginaw and Thunder bays in Lake Huron, (2) Green Bay in Lake Michigan, (3) the islands near Sandusky, Ohio in Lake Erie, and (4) near Hamilton, Ontario, and Bay of Quinte in Lake Ontario.
How Many Ciscoes Are Needed for Stocking in the Laurentian Great Lakes? | Journal of Fish and Wildlife Management

Funded In

Funding Agency


Restoration Framework Phase

Project Impact



Project Subjects