As state bioligists begin studying lake trout infiltration in Lindbergh and Holland lakes, Montana Fish, Wildlife and Parks approved a five-year extension of an experimental gill-netting project on Swan Lake but will reassess after two years to make sure bull trout numbers have not dropped below an established minimum threshold.
The extension allows Montana Fish, Wildlife and Parks biologists and professional fisheries consultants to continue removing lake trout during the fall as part of a study aimed at reducing non-native lake trout populations and helping native bull trout and kokanee populations rebound. Gill-netting will be conducted over a three-week period beginning late August or early September, according to FWP. State and Swan Valley Bull Trout Working Group personnel will remove spawning adult lake trout October and November along known lake trout spawning sites.
The results from the previous year will be made public by June of each year and evaluated to determine whether successful criteria are being met, FWP Regional Supervisor James Satterfield said in his letter approving the extension. Satterfield is also requiring that biologists establish a minimum threshold of bull trout numbers for the Swan drainage. This index will be compared to bull trout bycatch and abundance trends to determine if the project should be continued, modified or terminated, Satterfield said.
The original experimental project began in 2009 as a feasibility study to determine if gill nets could effectively reduce the number of non-native lake trout and improve conditions for bull trout and kokanee. FWP approved the experiment for three years. Biologists returned with an unclear understanding of long-term implications and asked for another five years to further test the effectiveness of gill-netting.
FWP received 127 written public comments by mail or email. Of those, 108 supported the proposed extension, 14 were opposed and five asked questions about the study but did not choose sides.
Lake trout continue to expand throughout the Swan drainage. While they were known to already exist in Lindbergh Lake, they were were discovered in Holland Lake in just the last year.
“While data is limited, it is suspected that lake trout establishment in these headwater lakes has the potential to negatively affect the bull trout populations they support,” Satterfield said in the decision notice.
He said future research should determine how much interaction these lake trout populations have with one another and examine how the populations influence removal efforts in Swan Lake.