Anchorage anglers got good news this week when Fish and Game reported that pesticide applied to Cheney Lake last October in an effort to wipe out invasive northern pike appears to have worked.
Since Monday morning, a Fish and Game crew has set out a dozen nets to see if any fish survived the application of rotenone. So far, said regional management biologist Matt Miller today, they've yet to bring up a pike -- though one blackfish, a sluggish bottom-dweller, has been netted. The effort continues through Friday.
Rotenone kills animals with gills by inhibiting their ability to use oxygen, but it has been proven safe for humans and animals lacking gills.
If no pike are found, Fish and Game plans to start stocking the lake with rainbow trout at the end of the month. The non-native pike had wiped out Cheney Lake trout and have decimated fish in a variety of Southcentral waterways.
Rotenone, a naturally occurring chemical that comes from a member of the bean family, poses little threat to mammals or humans in the amounts used.
According to a manual on rotenone distributed by the American Fisheries Society, a professional society for fisheries scientists, a 160-pound person would have to drink 23,000 gallons of water treated at 0.25 milligrams of rotenone per liter of water (the highest allowable treatment rate for fish management) at one sitting to receive a lethal dose.
The chemical also typically breaks down within days and binds quickly to soil, limiting its spread.
Officials are asking residents to keep dogs under control near the lake and not risk entanglement with Fish and Game's nets.
"We've gotten an overwhelmingly favorable response from the people living near Cheney Lake," Miller said. "A lot of longtime residents want to get back rainbow fishing."
Cheney Lake off Baxter Road in Muldoon used to be one of the most popular lake fisheries in the Anchorage Bowl, attracting a regular stream of anglers throughout the summer in canoes, float tubes and paddleboats.
State biologists started stocking it in 1982 and some years poured in more than 20,000 rainbow trout and landlocked salmon, said Dan Bosch, the Anchorage-area sport fish biologist for Fish and Game.
Biologists stopped stocking in 2001 after pike were discovered.
Pike thrive in shallow waters, where they feed on insects, frogs and other fish. They are not native to Southcentral Alaska.
The department has tried to eradicate the pike in Cheney Lake by gillnetting them and by encouraging anglers to target them, but it hasn't been enough to wipe out pike, Bosch said. The lake is in a former gravel pit so it has no native fish population, he said.
By MIKE CAMPBELL
mcampbell@adn.com