SWAN LAKE – If fish and wildlife managers decide to use gill netting as a method of lake trout removal in Flathead Lake, they will undoubtedly look to a project at nearby Swan Lake for guidance.
But they also know only so much insight can be gained from such a different body of water. As Leo Rosenthal sees it, Swan and Flathead lakes are “apples and oranges” – different size, habitat and history. Rosenthal is a fisheries biologist for Montana Fish, Wildlife and Parks.
One constancy, however, that Rosenthal and other fisheries managers agree upon is that non-native lake trout – or mackinaws – inhibit the recovery of bull trout, a native fish species that has been protected by the Endangered Species Act since 1998.
“There’s been a lot of work put into protecting the habitat for bull trout,” Rosenthal said. “Right now, their biggest threat is lake trout.”
Rosenthal is involved in a three-year gill netting effort on Swan Lake, along with other fisheries biologists, including Wade Fredenberg of the U.S. Fish and Wildlife Service. After tracking lake trout and conducting population studies, biologists began netting in 2009.
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A lake trout caught in a gill net is pulled out of Swan Lake and on the boat for processing. |
Last week, a professional fishing crew was wrapping up the second year of netting for juvenile lake trout. The adult harvest will take place later this month. A company named Hickey Brothers, out of Baileys Harbor in Wisconsin, is carrying out the netting, assisted by the biologists.
Meanwhile, an environmental assessment determining how to manage lake trout in Flathead Lake is nearing completion, with a draft likely by the end of the year.
In December of 2009, the Confederated Salish and Kootenai Tribes released a draft pilot project proposal to decrease the lake trout population in Flathead Lake by 25 percent by 2012 through a combination of angling and gill netting.
The tribes and FWP have co-managed Flathead Lake for 10 years, but the co-management plan expires at the end of this year. The goal of the cooperative effort has been to rejuvenate native bull trout and westslope cutthroat populations by diminishing lake trout numbers through angling – particularly the twice-annual Mack Days fishing tournament.
The tribes are responsible for management on the south half of the lake, and FWP is responsible for the north end. While both sides have expressed a desire to continue co-management, the tribes have reserved the right to move unilaterally.
The gill netting proposal irked lake trout anglers and charter fishing guides. After a series of public meetings, heavily attended by anglers and guides, the tribes backed off their plans and said they were investigating alternative management methods, which would be researched through the environmental assessment process.
Last week, Tom McDonald, manager for the tribes’ fish, wildlife, recreation and conservation division, said that continuing management through angling is the most desirable option.
“If we can reduce the population by just angling, boy, everybody wants to do that,” McDonald said. “That spring (Mack Days) was great. If we can build on that, we’re very optimistic we can produce some results. But we have to have a backup plan.”
Led by the strong Mack Days’ catch, McDonald said angling alone should achieve the tribes’ goal of removing at least 60,000 lake trout this year. The gill netting proposal called for removing 60,000 lake trout in 2010, 80,000 in 2011 and 100,000 in 2012.
McDonald anticipates a successful Fall Mack Days event, scheduled for Oct. 1 through Nov. 14. After reviewing those harvest numbers and the subsequent environmental assessment report, the tribes and FWP will have a better idea of how to move forward with management. McDonald said the environmental analysis has fielded a wide range of comments and suggested management methods.
“The biggest thing is that it’s taking more time to analyze alternatives, because there’s a quite a few that have come to the table,” he said.
Some anglers on Flathead Lake remain skeptical, as evidenced by an anti-gill netting demonstration on Sept. 14 at FWP regional headquarters in Kalispell. Tim Shattuck, one of the protest’s organizers, is a guide for Flathead Lake Charters.
He said his fish catch has decreased from 12 lake trout on an average four-hour boat trip to three. Those numbers, he said, indicate that suppression efforts have already taken a toll on the lake trout population.
“You can’t tell me it’s because I don’t know what I’m doing,” Shattuck said. “People come a long way to fish and spend a lot of money in our local economy. There are other options. Netting ain’t the right option.”
Over on Swan Lake, Rosenthal said conditions are likely more conducive to an effective gill netting campaign. Swan Lake isn’t nearly as deep, nor is its lake trout population as established.
Rosenthal said the mackinaws are thought to have moved up from Flathead Lake into the Swan beginning in the 1950s when a fish ladder was installed at the Bigfork Dam. The ladder has since been disabled.
As with the Flathead, biologists say the population exploded in the 1980s after mysis shrimp established themselves. The shrimp had been introduced to the region by FWP in the late 1960s.
But unlike Flathead, Swan Lake isn’t a major lake trout fishing destination, Rosenthal said, nor does it have a large commercial charter base. This makes gill netting there less controversial.
“From a recreational standpoint, there’s not enough of a population to make the fishing that good,” Rosenthal said.
Furthermore, the bull trout population is doing pretty well. Swan Lake is one of the few bodies of water in Montana where anglers can keep bull trout. An angler is allowed to keep one bull trout per day. Since 2004, Rosenthal said anglers have also been able to keep two bull trout per year with a “catch card” on Hungry Horse Reservoir and Lake Koocanusa.
“To have enough (bull trout) in the lake that you can still fish for them, for me, is a huge thing for Montana,” Rosenthal said of the Swan.
Gill netting is an effective method of catching fish and has been used for decades in Montana for research purposes. But as a fish removal method, targeted specifically at lake trout, it is a new endeavor in the Treasure State.
Rosenthal has been pleased with the results in the Swan, which will undergo one more year of netting in 2011. But he said it’s difficult to gauge success until biologists have enough time to wade through the mounds of data being collected.
Operating a boat named Trygg, the Hickey Brothers crew and biologists set out a series 900-foot-long gill nets in Swan Lake, sometimes covering more than two miles. The project takes place in the fall when many bull trout are up in tributaries spawning, to reduce bull trout by-catch. A recovery tank is used to revive any captured bull trout, though not all survive.
In 2009, about 5,200 juvenile and 239 adult lake trout were captured, Rosenthal said. As of Sept. 8 of this year, the team had caught more than 8,000 juvenile lake trout, along with 185 bull trout.
There are also gill netting projects occurring in Yellowstone Lake in Wyoming’s Yellowstone National Park, in Idaho’s Lake Pend Oreille, and in Glacier National Park’s Quartz Lake. And if comparing Swan and Flathead is apples and oranges, Quartz is another fruit altogether.
Clint Muhlfeld, a research aquatic ecologist for the U.S. Geologic Survey stationed in the park, said of the 12 barrier-free lakes connected to Flathead Lake’s tributary system in the park’s western portion, nine have been invaded by lake trout and a 10th by brook trout, another char species. But Quartz’s lake trout population is the least established and Muhlfeld figures bull trout have the best chance of thriving there.
“It’s basically the last of the best,” Muhlfeld said. “I think we got there in the nick of time.”
With Quartz’s small size, lack of mysis shrimp and specific spawning destinations, Muhlfeld said the harvest rate, or “exploitation rate,” for adult lake trout has been greater than 90 percent, with 10 out of 11 tagged fish captured last year. The Quartz netting project is planned for four years.
“Overall our first year was really promising,” Muhlfeld said. “I’m not aware of any other exploitation rate that high anywhere, including the Swan.”
Keeping an eye on the Quartz and Swan projects, and awaiting the results of the environmental assessment, officials for the tribes and FWP know they have big decisions on the horizon. But McDonald says, while the method of lake trout suppression is undetermined, the goal is clear.
“It would be a crying shame to see the bull trout in Flathead Lake blink out,” McDonald said. “They’re a signature species. They’re an icon for the state and, boy, it’s just the right thing to do to try to recover bull trout.”