Spawning Habitat Unsuitability: An Impediment to Cisco Rehabilitation in Lake Michigan?

Abstract

The cisco Coregonus artedi was one of the most important native prey fishes in Lake Michigan and in the other four Laurentian Great Lakes. Most of the cisco spawning in Lake Michigan was believed to have occurred in Green Bay. The cisco population in Lake Michigan collapsed during the 1950s, and the collapse was attributed in part to habitat degradation within Green Bay. Winter water quality surveys of lower Green Bay during the 1950s and 1960s indicated that the bottom dissolved oxygen (DO) concentration was less than 2 mg/L throughout much of the lower bay, and most cisco eggs would not successfully hatch at such low DO concentrations. To determine present-day spawning habitat suitability in lower Green Bay, we compared cisco egg survival in lower Green Bay with survival at a reference site (St. Marys River, Michigan–Ontario) during 2009. We also conducted winter water quality surveys in lower Green Bay and the St. Marys River during 2009 and 2010. Cisco egg survival in lower Green Bay averaged 65.3%, which was remarkably similar to and not significantly different from the mean at the St. Marys River site (64.0%). Moreover, the lowest bottom DO concentrations recorded during the winter surveys were 11.2 mg/L in lower Green Bay and 12.7 mg/L in the St. Marys River. These relatively high DO concentrations would not be expected to have any negative effect on cisco egg survival. We conclude that winter water quality conditions in lower Green Bay were suitable for successful hatching of cisco eggs and that water quality during the egg incubation period did not represent an impediment to cisco rehabilitation in Lake Michigan. Our approach to determining spawning habitat suitability for coregonids would be applicable to other aquatic systems.

Received May 14, 2011; accepted July 6, 2011

ACKNOWLEDGMENTS

We thank the Chippewa Ottawa Resource Authority biologists and MDNR biologists who captured adult ciscoes from the St. Marys River. We are also grateful to Martha Wolgamood (Wolf Lake State Fish Hatchery) for advice and assistance; Matt Hughes and Scott Zajac (Wolf Lake State Fish Hatchery) for hatchery assistance; Peter Boma for piloting the airboat and assisting in the field; Jeff Allen and Glen Black for scuba diving efforts during egg retrieval; Jon Molenhouse, Brandon Spude, Michael Fainter, and David Sena for dedicated efforts in the winter water quality survey work; Geoffrey Steinhart and his graduate students at Lake Superior State University for winter water quality survey work at the St. Marys River site; and Christine Joseph, Minako Kimura Edgar, and Lacey Mason for GIS assistance. We appreciate the storage space and logistical support provided by the U.S. Fish and Wildlife Service Green Bay Fishery Resources Office (New Franken, Wisconsin). Harold Mohr kindly provided winter access to the St. Marys River site. Doran Mason and Craig Stow reviewed the draft manuscript and made helpful suggestions for its improvement. Use of trade, product, or firm names does not imply endorsement by the U.S. Government. This research was funded by a Great Lakes Fish and Wildlife Restoration Act grant (U.S. Fish and Wildlife Service) to E.S.R and C.P.M. This article is Contribution Number 1656 of the U.S. Geological Survey, Great Lakes Science Center and is Contribution Number 1595 of the Great Lakes Environmental Research Laboratory.