Cisco in Indiana: Managing a Cold-Water Species Along Its Southern Range Limit

Glacial lakes in northern Indiana constitute the southern native range extent of Cisco (Coregonus artedii) in North America. Over the past 100 years, the number of inland glacial lakes in Indiana with Cisco present has declined precipitously, from approximately 45 in the early 1900s to 7 in 2013.  Unlike many Midwestern glacial lakes located further north, most glacial lakes in Indiana are surrounded by intensively-farmed agricultural land. Thus, while the mechanisms of these numerous local extirpations have generally not been systematically evaluated, managers generally suspect that high agriculture-related nutrient loading has contributed to frequent hypolimnetic hypoxia, which may be incompatible with persistence of cold-water Cisco. With continued climate warming, the squeeze of low oxygen from below and warm temperatures from the top of the water column may further reduce the likelihood of persistence of Cisco in Indiana lakes may further diminish. In the light of these stressors, the most suitable management actions to ensure persistence of Cisco in individual lakes in Indiana is unclear. We will discuss recent efforts to assess Cisco in Indiana lakes, including their genetic variability, develop models to describe their likelihood of persistence and prioritize their management in the state.