Mack Days suppression effort expands

The Spring Mack Days fishing tournament is just around the corner, and organizers are looking for the event to remove about 9,000 more lake trout from Flathead Lake than last year’s event.

The Mack Days fishing tournament began in 2002 and is sponsored by the Confederated Salish and Kootenai Tribes. It is sanctioned by Montana Fish, Wildlife and Parks. The tournament is part of the tribes’ ongoing efforts to reduce the amount of non-native lake trout in Flathead Lake to hopefully bolster populations of native fish such as the bull trout. The annual spring event is March 20-May 17. There is also a Mack Days in the fall.

Flathead Lake had been co-managed for 10 years by the tribes and Montana Fish, Wildlife and Parks up until 2010, when their co-management plan ended. The tribes decided on their own to pursue gill netting, which the state has opposed. The tribes’ goal is to reduce predation from non-native lake trout on native bull trout. There currently is no co-management plan between the state and the tribes. The tribes manage the south end of Flathead Lake, while the state of Montana manages the north end.

Last spring, Mack Days removed about 31,000 lake trout from Flathead Lake. Combined with the tribes’ first season of gillnetting and the fall Mack Days event, about 77,000 lake trout were removed from the lake in 2014, CSKT fisheries biologist Barry Hansen said. Hansen said that number is still too low to make the kind of impact they want to see in reducing non-native lake trout in Flathead Lake.

To increase the numbers of fish harvested in Mack Days, this year the derby has added weekday competition. The addition of weekday fishing to the competition gives anglers 51 days to catch a tagged fish worth over $10,000, or increase their winnings by catching over 1,200 fish. For every fish an angler catches the fisherman receives one ticket for the season-end lottery. Once an angler reaches a certain number of fish, they are paid a bonus. Up to $225,000 in cash and prizes will be awarded.

 “Lake trout have been pretty much at a level where they largely self regulate,” Hansen said. “They have a large critical mass that they can sustain and there’s a certain level of harvest that’s sustainable. That’s the tipping point we need to reach.”

The tribes monitor the lake trout population largely through tagging, as well as other survey methods.

Hansen said gillnetting was added because the tournaments were not enough to reduce lake trout, or mackinaw, populations. “It has confirmed that the harvest to date hasn’t really been able to affect population size,” Hansen said. “That’s exactly why we initiated gillnetting, because we just couldn’t get that crucial harvest with angling alone.”

Fish that are caught in Mack Days are processed and donated to local food banks.

Last year, tribal biologists aimed to remove 90,000 lake trout from Flathead Lake between two seasons of gillnetting and spring and fall Mack Days. They fell short of the target by about 13,000 fish.

This year they would like to harvest 98,000 lake trout.

“To get there we have to expand the efforts that we’ve done in the past,” Hansen said. “One good way to do that is expand and modify the Mack Days contest. So we thought this year we would expand to weekdays.”

“So many people work during the week, we want this to be as fair as possible,” Mack Days technician Cindy Benson said.

In addition to expanding Mack Days the tribes are also going to gillnet for eight weeks in the spring. Last year they gillnetted for two weeks.

“We are slowly building the program,” Hansen said. Tribal biologists are also learning how to catch only lake trout, and not the native fish — like bull trout — they are trying to protect.

The first year of gillnetting went fairly well for the tribe as far as native fish mortality, Hansen said. They were able to remove about 8,000 lake trout, and had one bull trout casualty.

“Our intent is to maintain that kind of ratio,” he said. “Lake trout are a serious predator on bull trout and we’ve got to reduce their numbers to benefit bull trout.”

The tribes started spring gillnetting last week, and will wrap up in May depending on the weather. They will be netting during the derby as well as tagging more fish for anglers to catch.

While tagging fish is primarily a way for biologists to track populations, tagged fish caught in the Mack Days contest are often worth cash prizes ranging from $100 to $10,000. More fish will be tagged before the event begins, and tagging will continue throughout the event.

More information about spring Mack Days, gilnetting and the lake trout suppression effort can be found at www.mackdays.com