In 2002, Spring Lake and Upper Prior Lake were listed on Minnesota’s 303(d) List of Impaired Waters for nutrient/eutrophication biological indicators and aquatic recreation on both lakes is impaired. The 2012 Spring Lake and Upper Prior Lake TMDL Implementation Plan identified internal loading, including the load from rough fish and curly-leaf pondweed, as a source of roughly half of the phosphorus internal loading to the lakes. The plan went further to identify rough fish management as a way to significantly reduce estimated P loading.
The District’s carp management project maximizes water quality restoration and remediation by addressing one of the root causes of internal loading identified in the TMDL for Spring and Upper Prior Lakes. Carp re-suspend sediments making phosphorus available to phytoplankton and increasing the shading effect on native submergent aquatic vegetation, sequestering phosphorus. Carp also feed directly on or uproot vegetation, further increasing the level of phosphorus in the water column. By removing the carp from the system, both the phosphorus within the carp carcass and the amount that would typically be excreted will be completely removed, while also abating the release of phosphorus created by foraging behavior.
This project uses integrated pest management (IPM) principles to effectively manage the common carp population within the basin. IPM involves the use of targeted carp removals and barriers, as well as monitoring environmental parameters that can inhibit or promote carp population growth within the Spring and Prior Lakes basins. Adaptive management will use data that is collected on the carp population with respect to population and biomass estimates as well as migration routes and winter aggregation locations.
To read a Scott County SCENE article on the project, please click here.
