The airplane swooping across the pond at Bruneau Dunes State Park wasn’t a military exercise by the nearby Mountain Home Air Force Base, but the plane was 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. The fishing quality had dwindled, so Idaho 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, and it appears they succeeded.
“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. Most of the bass were undersized - in the 8-inch range - and only one reached the prized 20-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. 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. 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.
Now the pond will soon be ready to be restocked with bass and bluegill. Prior to the October treatment, Fish and Game crews electrofished the pond and moved largemouth bass and bluegill to a nearby pond for restocking after the rotenone.
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. Biologists expect the Bruneau Pond could be fully restored in three to five years and return to its former reputation for abundant bluegill and trophy-sized largemouths.
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.
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.
Photo information
Airplane: Photo by Scott Stanton/Idaho Fish and Game
Suggested cutline: An airplane from Valley Air in Nampa sprays rotenone over the Bruneau Dunes Pond.
Dead carp: Photo by Scott Stanton/Idaho Fish and Game
Suggested cutline: Fish and Game crews removed hundreds of dead carp from the pond, which will reduce competition on game fish.
Boat: Photo by Kelton Hatch/Idaho Fish and Game
Suggested cutline: Prior to using rotenone, crews electro fished the pond and removed bass and bluegill to be restocked after the treatment is complete.
Pond: Photo by Kelton Hatch/Idaho Fish and Game
Suggested cutline: Bruneau Dunes Pond is a scenic fishing spot and popular with anglers, so Fish and Game wants to continue providing a quality fishing opportunity there.