An Analysis of Lake Morphometric and Land-Use Characteristics that Promote Persistence of Cisco in Indiana

Remnant populations of Cisco Coregonus artedi persist at the southern extent of their range among northern Indiana's glacial lakes, where most of their populations have become extirpated during the past century. Land-use practices have likely accelerated lake eutrophication, while climate change threatens to further degrade the habitat necessary to sustain Ciscoes in Indiana. However, because the effects of these stressors have not been ubiquitous, an understanding of the factors that have contributed to either extirpation or persistence of Cisco populations will better inform future conservation practices. We analyzed lake morphometric and land-use data to identify lakes that (1) are most likely to sustain Ciscoes, (2) are most likely to lose Ciscoes, and (3) have lost Ciscoes but are similar to current Cisco lakes and hence may be targets for restoration. We found that large, deep lakes located further north were more suitable for Ciscoes in the past, but that smaller lakes with a high ratio of lake area to catchment area have retained Cisco populations. This pattern supports the hypothesis that non-point-source nutrient loading is a driver of Cisco extirpations. Our results provide information to better manage a species of special concern in Indiana and of conservation interest in many other areas. Received August 5, 2015; accepted November 20, 2015