The cutthroat trout conservation team at Yellowstone National Park expects to break a record this year, ridding Yellowstone Lake of more than 360,000 lake trout. The high mark was set last year, with 358,000 removed from the lake.
“They’re on a record pace,” said Jonathan Shafer, Yellowstone public affairs officer.
There are 35 to 40 miles of nets in the lake every day during the mid-May to mid-October effort. Crews made up of both Park Service employees and subcontractors man the nets six days a week in an attempt to crash the lake trout population. The trout, which feed on the native cutthroat trout, were introduced in the lake in the late ’80s or early ’90s. DNA results show the lake trout were brought from Lake Michigan.
Comparing numbers, about 12,000 lake trout were removed from the lake in 2002. At the time, program director Todd Koel thought they were doing pretty good. But, unknown to Koel, lake trout populations were growing exponentially. Six years later, the crew realized what they were up against.
“In 2008, I was told to double my efforts and expect to be doing it for a long time,” Koel said.
Koel expects his crew to continue netting lake trout through mid October — when inclement weather forces the crews off the lake and into the lab until the spring thaw. At the same time, the team is concentrating much of their efforts on embryo suppression during the lake trout spawn. The team uses both sediment and ground lake trout to kill the eggs on spawning beds, giving the team what may prove to be the deciding advantage.
“We keep ramping up the effort,” Koel said while checking on the several boat crews enlisted in the effort on the high altitude lake.
Embryo suppression is tough. Some of the spawning areas are in more than 50 feet of water. The crew started catching mature lake trout, putting transmitters in the fish and returning them to the lake. The fish, known as Judas fish, head to spawning areas and the crew then target the areas for netting fish and embryo suppression.
The crew had planned to use an airplane to track Judas fish this season, but the weather never cooperated, so the fish have been tracked by boat. With large hydrophones mounted to the sides, two boats move at 5 mph, covering the entire lake in two days. It makes for very long days on the 26-mile-long, remote lake.
After finding the spawning sites, two teams are directed there. Netting boats sink nets in the area to catch as many of the fish as possible. Dead fish are then transferred to the embryo suppression team, which throws them in grinders mounted to the side of their boat and drops the biomass on the spawn sites — which kills the eggs. A single female lake trout can lay about 5,000 eggs.
It’s all about killing the fish. The team members are competitive in their efforts and spend much of their time researching ways to kill more of the fish while doing their lab work. A group of graduate students from Montana State are also currently doing research on the efficacy of the embryo suppression efforts and the effects of the nutrients from the ground fish flowing through the ecosystem. One thing is obvious: The gulls love the project.
While debates continue through the summer on who is killing the most fish, few on the crew are as competitive as Phil Doepke. He has nothing against lake trout — nobody on the crew does — but the goal is to save the native fish and the only way to do that is to kill lake trout. The more the better.
“I’m a big fan of lake trout; they’re a wonderful fish,” Doepke said. “These are just in the wrong place.”
The effort is working. Crews are seeing fewer large lake trout in their nets and the Yellowstone cutthroat trout populations are rebounding. And as the cutthroats return to what was once a common site, grizzlies feed on the tasty fish in the rivers and tributaries of the massive lake.
“We’re winning not only in the lake, but also in the streams,” Koel said.
There are also 15 to 16 bald eagle nests on the shores of the lake, but so far osprey have not returned to feed on cutthroats.
The program is funded in part by fishing license and gate fees as well as a $1 million donation from Yellowstone Forever, the park’s official nonprofit partner. The park sold about 45,000 fishing licenses this year. Not including salaries, the program costs about $2 million per year, Koel said. Netting contractors are the largest expense in the budget. Nearly 3 million lake trout have been removed since the program began.