Traditional methods for surveying aquatic communities are often costly, destructive and ineffective. The Canadian federal government spends more than $500M per year on environmental monitoring activities which involve more than 2500 people (estimate based on December 2011 report of the Canadian Commissioner of the Environment and Sustainable Development). Industries spend an additional $300M on environmental monitoring. For example, our industrial partner, WSP Canada Inc. spends about $750,000 per year to monitor fish communities in impacted habitats. Molecular methods based on DNA isolated from environmental samples (eDNA) can considerably lower the costs of aquatic ecosystem assessment, particularly when assessing rare and endangered species. To date, significant attention has been placed on refining eDNA-based techniques to accurately capture and sequence the DNA released in the environment and to accurately determine the species present. However, we are still missing information on the "behaviour" of eDNA - how it is created, transported and degraded. These processes influence the chance of accurately determining species presence from molecular samples. For example, few studies have examined the role of seasonal water movements in lakes and how this influences the distribution of eDNA. We propose to sample dimictic lakes during summer months when water is stratification and during spring and autumn water turnover. We will sample the water column to create an eDNA depth profile and will validate the method using radio-telemetry tagging of lake trout. The proposed study will contribute to our understanding of the "ecology" of eDNA and its distribution within lentic systems. Moreover, this study will help WSP plan eDNA sampling campaigns, by taking into consideration how seasonal water movements influences the distribution of DNA molecules. Our results will be also applicable to anyone undertaking a comprehensive eDNA sampling campaign, such as academics, industry and government.*