Purging of fish successful so far

State poisoning hybrids in two Jewel Basin lakes

The state's first go at purging hybrid fish populations from two lakes in the Jewel Basin came off without a hitch, the last of the work being finished this week, the project coordinator said.

"Logistically, they went off extremely well," said Matt Boyer, a fisheries biologist with Montana Fish, Wildlife and Parks.

The work on Black and Blackfoot lakes was the start of a 10-year project that will focus on eliminating hybrid fish populations in 21 alpine lakes that are connected to the South Fork Flathead River basin, a stronghold for native westslope cutthroat trout. The state's concern is that hybrid mixes of rainbow trout and westslope and Yellowstone trout threaten to "leak" into the greater basin, corrupting a genetically pure fish population.

Treated lakes are to be restocked with genetically pure westslope cutthroats.

The recent work in the Jewel Basin was logistically challenging, involving a single engine air tanker, a boat, and drip stations to apply a natural fish toxin called rotenone to the two lakes. Trails to the lakes were temporarily closed when the work was under way.

The work on 147-acre Black Lake was carried out Sept. 25-28, with the SEAT tanker releasing 1,300 gallons of rotenone in three drops. A helicopter brought in an additional 7 barrels of rotenone that was applied by an airlifted boat and through drip stations on two inlet streams and one outlet stream.

Boyer said he's confident the kill success was 100 percent, taking out "thousands" of fish. Just more than 350 were netted from the surface, and judging from the water temperature, Boyer estimates that 70 percent of the fish sunk to the lake's bottom.

The netted fish, ranging from fry on up to 18-inch fish, were sunk in the lake with a poke to their air bladders. The fish cleanup was necessary partly remove smelly bear attractants from the shoreline and also to provide a nutrient base for a new fishery. Boyer said the lake will be restocked with finglerings and a limited number of fish that are of catchable size next spring.

"We expect the initial growth rates for these fish to be extremely high" because they are not being planted on top of an existing fishery, he said.

The work on the 16-acre Blackfoot Lake was carried out Tuesday with helicopter support, a boat applying the rotenone and drip stations on inlet and outlet streams. It will also be restocked with westslope cutthroats next spring.

Boyer and others at Montana Fish, Wildlife and Parks are anxious to see an analysis of genetic samples collected from all 21 alpine lakes over the summer. While similar work has been done in the past, confirming the presence of hybrid populations, the summer sampling work will provide the most recent picture of how extensive hybridization is in the lakes.

When the project was first proposed in 2001, it was met with stiff opposition from different quarters. Wilderness advocates objected to the use of aircraft and motorized equipment in lakes that are located inside the Bob Marshall Wilderness Complex. Outfitters and backcountry anglers were skeptical of the necessity to kill off popular fisheries.

A lengthy environmental review - jointly conducted by Montana Fish, Wildlife and Parks, the U.S. Forest Service and the Bonneville Power Administration - attempted to address some of those concerns and others.

Some lakes, for instance, will be accessed with packing stock rather than aircraft. Concerns about potential impacts to amphibians were addressed by a commitment to carry out lake treatments in the fall, when frogs and salamanders are not vulnerable to a toxin that is effective only on gill breathing organisms.

The project was at one point estimated to cost about $2.5 million, but the price tag was expected to fluctuate based on rotenone costs and the methods used to apply the chemical. The work is being entirely funded by BPA through its mitigation program for dams such as the Hungry Horse project, which impacted fisheries throughout the Flathead river system.

Reporter Jim Mann may be reached at 758-4407 or by e-mail at jmann@dailyinterlake.com