Thursday, Jan 26, 2012
Staff at Sequoia and Kings Canyon National Parks recently completed a decade-long project that allowed a population of imperiled mountain yellow-legged frogs to stage an impressive recovery. This was done through the removal of non-native fish from a large and challenging complex of high-elevation lakes and streams.
Mountain yellow-legged frogs (Rana muscosa and Rana sierrae) inhabit naturally fishless lakes, ponds and streams in the Sierra Nevada and at one time were the most numerous amphibians in these mountains. Today, they have disappeared from 92% of their historic range, including Sequoia and Kings Canyon National Parks, and are candidate species for listing under the federal and California Endangered Species Acts. Extensive research identified two main factors for the decline: negative effects from non-native fish (various introduced trout species) and disease (chytridiomycosis, caused by amphibian chytrid fungus).
To address effects from non-native fish, the parks began using gill nets and electrofishers (devices that temporarily stun fish) in 2001 to remove fish from selected lakes and associated streams. By 2011, nearly 44,000 fish had been removed from 19 lakes, including complete removal from nine lakes.
Three of the completed lakes are located in the Upper LeConte Canyon area of the parks. From 2001, when fish removal began, to 2004, when most of the fish had been removed, the number of mountain yellow-legged frogs in these three lakes increased from nearly 190 to over 18,800 – a 10,000% increase.
From 2005 to 2011, during the removal of the remaining few fish, the population of mountain yellow-legged frogs in these lakes stabilized, with numbers ranging from a 1,900-6,000% increase.
In addition, over 2,000 frogs moved into two nearby lakes. As a result, this mountain yellow-legged frog population is now in a much stronger position to deal with other threats, such as disease.
For more on this story, visit http://www.nps.gov/seki/naturescience/mountain-yellow-legged-frogs.htm.
To learn about a related plan and draft environmental impact statement to potentially restore additional sites, visit http://www.nps.gov/seki/parkmgmt/rheae.htm.