Modification to Mountain Lakes Fishery Management Plan - Piscicide Change from Antimycin to Rotenone (2013)
Over the past four years North Cascades National Park Complex has been working hard to restore several mountain lakes within the park, in accordance with our Mountain Lakes Fisheries Management Plan (MLFMP), by removing non-native, self-sustaining populations of fish from several lakes. Spawning habitat exclusion has been tested in one lake, intensive gill netting is currently being used to remove fish from six lakes, and antimycin has been used in two lakes. Monitoring results following these efforts indicate native species such as the tailed frog and long-toed salamander are rapidly returning to these naturally fishless ecosystems as the non-native populations of fish are removed from these naturally fishless lakes.
Now, in accordance with the MLFMP, North Cascades National Park Complex is preparing to continue our lake restoration efforts this fall by removing a reproducing population of non-native Eastern Brook Trout from Sourdough Lake. The goals of this high-priority effort are to restore the native ecology of Sourdough Lake and to protect the genetic integrity of Bull Trout, a federally threatened fish species which is native to lower elevation creeks and rivers. Brook trout dispersing downstream from Sourdough Lake have the potential to harm Bull Trout in Ross Lake and the broader Skagit River watershed.
As outlined in the MLFMP, successful restoration of Sourdough Lake requires treatment with a piscicide due to the size and depth of the lake. Although antimycin, specifically Fintrol™ a liquid form of the piscicide, was initially identified as the preferred piscicide in the MLFMP and was successfully used to treat Blum Lakes in 2010, this chemical is no longer commercially available and current stocks have been depleted. As a result, North Cascades National Park Complex is proposing to use a recently developed liquid formulation of rotenone known as CFT Legumine™ as the preferred piscicide for fish removal in lakes identified for chemical treatments in the MLFMP, including Sourdough Lake.
The MLFMP envisioned using rotenone to restore mountain lakes; however, the plan noted that if rotenone was to be used for fish removal actions in the future, additional analysis would be completed and opportunities for public comment would be made available. The EPA has concluded that the use of rotenone for fish control does not present a risk to humans or the environment when used according to the label instructions, and based on an assessment of the environmental and human health risks of using rotenone to implement the MLFMP, the NPS has determined that using CFT Legumine™ to remove non-native fish will not have higher adverse environmental impacts than using Fintrol™ because this newer formulation of rotenone is not as toxic to non-target organisms and humans as older formulations of the piscicide. The NPS also believes that rotenone could be more effective than antimycin in treating particularly deep mountain lakes, such as Sourdough, as rotenone, unlike antimycin, is able to penetrate more dense layers in a lake's thermal stratification.
In order to engage your review of this proposal, we are soliciting public comments during a 30-day public review period that extends through June 14, 2013. During this time, we encourage you to learn more about our lake restoration program by checking out the documents linked to this project website and to provide feedback on this proposal by submitting comments on the whitepaper that is currently open for public review. Comments may also be submitted via regular mail to North Cascades National Park Complex, 810 State Route 20, Sedro-Woolley, Washington, 98284.
We look forward to hearing your input and appreciate the opportunity to share with you some information about the restoration of mountain lakes within the North Cascades.
Ashley Rawhouser, Aquatic Ecologist, 360-854-7317.