A so-called 'amnesty pond' for dumping unwanted fish is being planned at a park in San Francisco.
The announcement follows the poisoning by officials of the four-acre Mountain Lake (pictured above by Daniel J. McKeown, Creative Commons), to remove alien species in an attempt to restore populations of native Three-spined sticklebacks, chorus frogs and Western pond turtles.
The lake had become a dumping ground for goldfish and other species over the years. In the past, officials had tried using nets and electro-fishing to remove these fish, but it hadn't proved very successful. As a result, the lake was recently poisoned using CFT Legumine, which contains the active ingredient rotenone — a botanical material that degrades quickly.
The bodies of more than 850 non-native fish were retrieved after treatment — mainly goldfish, but there were also koi, catfish and bass.
It's hoped that re-stocking with native species can begin in May next year.
The amnesty pond will be built elsewhere in Mountain Lake Park to allow people to continue dumping their unwanted fish without having an impact on the native population.
The Presidio Trust, which oversees Mountain Lake, is spending $12m on a restoration project — reported by the San Francisco Chronicle to be the first of its kind — that will restore the lake to the way it was before Europeans arrived in America.