Date of Award

Fall 2014

Degree Type


Degree Name

Master of Science (MS)


Forestry and Natural Resources

First Advisor

Tomas O. Hook

Committee Member 1

Steven B. Donabauer

Committee Member 2

Andrew J. DeWoody


The cisco Coregonus artedi is distributed throughout northern North America and is relegated to coldwater, oligotrophic systems. Populations of cisco located at the species' southern range extent, including northern Indiana and southern Michigan, have drastically declined over the past century, seemingly due to a combination of climate warming and exacerbation of hypolimnetic hypoxic conditions via intensive land-use and resulting increases in nutrient loading. Apart from their decline, information on southern ciscoes is lacking, including basic stock demography and genetic variability. Such information may shed light on the likely sustainability (or lack thereof) of remaining populations. The first portion of this study aimed to (1) establish a baseline understanding of the stock biology of southern cisco populations, (2) assess the potential risk of extirpation among populations via assessments of stock biology and an analysis of intra-population genetic variation, and (3) explore the population history of southern ciscoes and assess their viability for conservation usage by examining inter-population genetic variation. Results indicate that southern cisco populations exhibit relatively consistent recruitment success and generally balanced sex ratios, indicating relatively healthy populations. However, the narrow size distributions exhibited in most lakes and the skewed sex ratios seen in some lakes may indicate sampling biases or the potential vulnerability of larger ciscoes and females to mortality events. An analysis of mitochondrial DNA sequences suggested that variation both within and among cisco populations is low; furthermore, this low variation may be exacerbated by selective mortality events. In contrast, microsatellite genetic analyses showed higher intra-population variation and suggest that all southern populations are genetically distinct. Taken in concert, these results indicate that the Crooked/Little Crooked and Indiana lakes populations are among the most sustainable, while the population in Eve Lake may be among the most likely to become extirpated.

While biotic factors influence population sustainability, the viability of southern ciscoes may depend heavily on abiotic factors due to their strict environmental (e.g., oxythermal) tolerances. The second portion of this study focused on analyzing lake morphometric and land-use characteristics in Indiana lakes which support cisco, versus lakes where cisco have been extirpated or never existed. In general, larger, deeper lakes were found to be more likely to have contained cisco (either currently or in the past). However, smaller lakes with larger ratios of lake area to total catchment area (i.e., headwater lakes) were more likely to contain current cisco populations than larger lakes. These results highlight the importance of minimizing nutrient loading, particularly from land-use practices, in preserving cisco populations.