Are cisco and lake whitefish competitors in the Great Lakes? Implications for future reintroduction efforts

Benjamin Rook (USGS, brook@usgs.org), Michael Hansen (USGS retired), Charles Bronte (USFWS)

The overall objective of this project was to evaluate historical commercial gill net fishery data available for State of Michigan waters of Lakes Superior, Michigan, and Huron for evidence of potential negative interactions between Cisco Coregonus artedi and Lake Whitefish C. clupeaformis. Catch per effort (CPE; kg/km of net) data from 20 individual commercial fishery management units (statistical districts) were corrected for lake- and species-specific changes in gill net efficiency (twine material) and used to test for correlations (positive and negative) between these species during 1929–1970. Akaike’s Information Criterion corrected for small sample size (AICc) was used to evaluate 13 a priori spatial models. The top three spatial models all had similar levels of support (ΔAICc < 3.0) and were used to determine if Cisco and Lake Whitefish CPE were correlated. Collectively, the top three spatial models had a 97% probability of containing the correct model of all models considered. Cisco and Lake Whitefish CPE were either not correlated or positively correlated for 12 of 13 pairwise (Cisco–Lake Whitefish) comparisons in these models. Although these findings cannot establish cause-and-effect, they do strongly suggest no interaction between Cisco and Lake Whitefish historically, and can be used to guide future coregonine restoration efforts throughout the Great Lakes.