An airplane swooping low across the pond at Bruneau Dunes State Park recently wasn’t a part of a military exercise by the nearby Mountain Home Air Force Base -- but the plane was definitely fighting an enemy.
The pond had become infested with common carp, an invasive fish that bred prolifically and outcompeted the pond’s bass and bluegill, according to the Idaho Fish and Game Department. The fishing quality had dwindled, so Fish and Game worked with Idaho Parks and Recreation to restore it.
“Park managers understand the importance of the fishery, and Idaho State Parks has been a great partner and has very supportive of the project,” said Regional Fishery Biologist Scott Stanton.
A Nampa-based flying company used two crop-duster planes to spray a fish toxicant known as rotenone across the surface of the 100-acre pond to kill the unwanted carp.
“We can never guarantee a complete kill, but things look pretty good so far,” said Doug Megargle, Regional Fishery Manger for the Magic Valley.
Fish and Game crews collected hundreds of dead carp from the pond and hauled them to a local landfill or a rendering plant in Hagerman. “Unfortunately, rotenone is nonselective, so the bass and bluegill remaining in the pond were also killed,” said Fish and Game spokesman Roger Phillips. “Most of the bass were undersized -- in the eight-inch range -- and only one reached the prized twenty-inch mark, which was evidence that carp were stunting their growth potential.”
The effectiveness of rotenone is short-lived and quickly broken down by sunlight, so the pond should be habitable for fish in about a week or two after the treatment, experts said.
“Removing carp not only eliminated the carp from competing with desirable game fish, it will likely improve the water quality and habitat of the pond,” Phillips explained. “Carp can strip a pond of its aquatic plants, and they will also burrow in the bottom for aquatic insects and other food on the bottom and stir up mud that clouds the water and inhibits sunlight that sparks plant growth.”
The pond will soon be ready to be restocked with bass and bluegill.
Stanton said crews stockpiled about 200 bass in a nearby pond. They may start transplanting those fish into the renovated pond during fall and winter, if weather and water conditions are favorable.
“In the spring, they will trap and relocate bass and bluegill from other waters in southern Idaho to help jump start the population,” Phillips said. “Biologists expect the Bruneau Pond could be fully restored in three to five years.”
Stanton said the project is to improve fishing opportunity for anglers, and re-establishing quality habitat is the first step, followed by restocking and managing the growing fish population.
Officials say killing and removing unwanted fish from ponds is a fairly common practice for Fish and Game, but it’s not one fisheries managers typically want to perform unless it’s needed. “It can be expensive and labor intensive, especially on larger ponds. But it’s also important for Fish and Game to continue providing the fishing quality anglers have enjoyed in the past, and the opportunity to enjoy it again in the future,” Phillips stated.