Historically, Cisco Coregonus artedi and Lake Whitefish C. clupeaformis were abundant throughout the Laurentian Great Lakes, but overharvest, habitat degradation, and interactions with exotic species caused most populations to collapse by the mid-1900s.  Strict commercial fishery regulations and improved environmental and ecological conditions allowed Cisco to partially recover only in Lake Superior, whereas Lake Whitefish recovered in all the upper Great Lakes (Superior, Michigan, and Huron).  The differential responses of Cisco and Lake Whitefish to improved environmental and ecological conditions in Lakes Michigan and Huron have led to questions about potential negative interactions between these species.  To provide context for fishery managers, we tested for positive and negative correlations between historical (1929–1970) Cisco and Lake Whitefish commercial gill net catch per effort (CPE; kg/km of net) at a variety of spatial scales in Michigan waters of the upper Great Lakes.  The three best-fit spatial models (LAKEWIDE, REGIONAL 10, and SIMPLE) all had similar levels of support ( [[EQUATION]] < 3.0) and were used to determine if Cisco and Lake Whitefish CPE were significantly correlated (positive and negative).  Cisco and Lake Whitefish CPE were either not correlated or positively correlated for most (12 of 13) pairwise (Cisco–Lake Whitefish) comparisons.  No strong positive or negative correlations were identified in the lakewide (LAKEWIDE) or reduced (SIMPLE) models.  In the regional model (REGIONAL 10), Cisco and Lake Whitefish CPE were strongly and positively correlated in two regions ( [[EQUATION]] = 0.59–0.71) and weakly negatively correlated in one region ( [[EQUATION]] = -0.45).  Collectively, our findings suggested that Cisco and Lake Whitefish CPE were largely independent of each other, which suggests these species did not interact to the detriment of one another in Michigan waters of the upper Great Lakes during 1929–1970.

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