Voyageurs National Park interior lakes status and impact assessment

LeDuc, Jaime; Maki, Ryan; Burri, Tom; Elias, Joan; Glase, Jay; Moraska Lafrancois, Brenda; Peterson, Kevin; VanderMeulen, David; Vondra, Ben

doi:10.36967/nrr-2289923

Voyageurs National Park (VNP) is a water-based park that includes part or all of four large lakes and twenty-six smaller lakes commonly referred to as “interior lakes”. The 26 interior lakes of VNP are important aquatic resources with differing size and depth, water chemistry, trophic status, fish communities, and visitor use. Despite the remote location of these lakes, they have been impacted by multiple stressors, including contaminants and non-native species. This assessment provides key information in support of a science-based management plan for these lakes. The objectives of this assessment were to: 1) assess the status of each of the interior lakes and categorically rank the lakes from least to most impacted; 2) use the results to make specific science-based management and restoration recommendations for the most impacted lakes; and 3) make general recommendations that may be useful in managing all of Voyageurs National Park’s interior lakes. When all factors considered in this analysis (water quality, fish mercury concentrations, and fish community characteristics) were combined and assessed, thirteen lakes were classified as most impacted, nine as moderately impacted, and three as least impacted. Although nearly half of the lakes were classified as most impacted in this assessment, many of these lakes are in excellent condition compared to other lakes in the region. The factor-by-factor impact status of the lakes was considered to help describe the condition of the lakes and the potential for restoration. No local management options were identified to mitigate the mercury contamination in these lakes as research has shown the sources of the contamination to arrive from regional and global sources. Similarly, no management actions were identified to reduce nutrient concentrations in the lakes ranked most impacted for nutrient conditions as these are remote lakes with minimal or no development within their watersheds, and it was also noted that paleolimnological studies have shown that the nutrient status of the interior lakes was relatively unchanged from pre-European settlement conditions. Finally, for the lakes in which presumed introduced fish species are present, piscicides were considered as a potential management action. Piscicides were not recommended as a strategy to eradicate introduced fish species as it was determined that genetic conservation of the populations of native fish species still present in these lakes was more valuable than eradicating the introduced species. The following general recommendations were made for management of these lakes to best maintain them in an unimpaired condition. 1. Continue to monitor water quality, fish assemblages, and mercury in the interior lakes of Voyageurs National Park. This monitoring provides baseline information necessary for maintaining resources in an unimpaired condition. 2. Make the current regulations and Best Management Practices (BMPs) for preventing introduction of aquatic invasive species (AIS) and fish diseases into the interior lakes permanent. The current regulations and BMPs protect the interior lakes from multiple invasion vectors and provide additional time for scientists to develop technologies for elimination or control for AIS and fish diseases. 3. Require visitors to watch a training video and to acknowledge having watched and understood the video before being issued a camping permit or boat reservation. The video should focus on Voyageurs National Park’s regulations and BMPs for preventing the spread of AIS and fish diseases and on the ecological repercussions of failing to follow the regulations and BMPs. 4. Continue to provide vessels for rent on some interior lakes. The rental system is straightforward and easy to monitor. Maintaining the current vessel rental program and adding additional vessels to that program, as appropriate, is the most reasonable option for preventing the spread of AIS and fish diseases while still...

Voyageurs National Park interior lakes status and impact assessment

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