Lake fisheries continue to change

By MIKE RICHESON

Bigfork Eagle

The future of Flathead Lake's fisheries is anybody's guess, but the past tells a chaotic tale of missteps and shifting fish populations. Dr. Bonnie Ellis addressed the topic during her State of the Lake presentation during the annual Flathead Lakers conference.

"There have been several major shifts since the early 1900s in the lake's fisheries," she said. "There have been huge increases in lake trout, which have increased 19 times, and there has been a four-fold reduction in native fishes."

The last 100 years has seen four major shifts in fish species: Native, kokanee, pre-mysis relicta (shrimp) and post-mysis, which is ongoing.

"We've really had four different lakes," Dr. Ellis said.

Before 1890, the lake was populated by native species including bull trout, westslope cutthroat trout, mountain and pygmy whitefish and northern pikeminnow.

Adding to the numerous native fish officially began in 1890, when 19 new fish species were introduced by federal and state agencies hoping to boost the game fish population. This effectively doubled the species diversity in the lake.

Railroads connected a system of fish hatcheries for transport to and from Flathead Lake. By the 1920s, the lake had an entirely new fishery in place. Along with a huge population of kokanee, lake trout, lake whitefish and the yellow perch took hold.

The kokanee fishing was boon to the economy. During the 30s, fishermen pulled 100 tons of kokanee out of the lake - each year.

By the late 1980s, however, kokanee had disappeared from the lake and the bald eagles that fed on the fish.

This occurred in part because in the 1970s, Fish, Wildlife and Parks introduced Mysis relicta, the opossum shrimp into Ashley, Whitefish and Swan lakes. The shrimp migrated downstream and colonized Flathead Lake, where the population exploded.

The problem with the shrimp, though, was that they avoided daylight. During the day, the shrimp would descend to the lake bottom and rise again to feed at night.

Kokanee, on the other hand, feed during the day and near the surface. These two species also competed for the same food source - zooplankton, tiny animals that live suspended in open water. Mysis was a better predator, however, and severely reduced the zooplankton population by 50 percent.

A recovery effort in the 1990s failed to reestablish kokanee.

Although the shrimp were not a food source for the kokanee, it became a favorite food for another fish - lake trout.

Juvenile lake trout feed on the bottom of the lake, and the mysis proved to be a rich and plentiful source of sustenance. These voracious eaters quickly became the dominant species in the lake at the expense of the bull trout and westslope cutthroat trout. Northern pikeminnow and the peamouth chub remain abundant, however.

In less than a decade, the main harvest from Flathead Lake changed from 90 percent kokanee to zero percent. By the early 90s, lake trout, lake whitefish and perch represented close to the entire fish harvest, with lake trout accounting for 55 percent.

In 1962, lake trout harvest was estimated at 1,248 fish. By 1992, that harvest increased to 21,656 - a 500 percent increase. By 1999, the numbers reached more than 42,000.

Management of the lake trout and native species is a touchy subject for many. The problem has been compounded by "bucket biologists" who transport more non-native fish into the system. The northern pike was illegally introduced in the upper Flathead River in the 1960s, and these fish have joined the lake trout as gluttons feasting on native bull trout and westslope cutthroat trout.

Because lake trout, yellow perch and lake whitefish are self-sustaining in the lake and river, Fish, Wildlife and Parks has tried to mitigate their impact by allowing extremely liberal limits on the daily take.

The yellow perch, which inhabits the shallow areas around Flathead Lake and the river sloughs, has a daily limit of 50 fish.

The angling limit on lake whitefish is also 50 fish daily, but the lake whitefish can be difficult to catch. During the fall, anglers usually have a good chance of catching this fish on the Flathead River. The Fish, Wildlife and Parks department has issued flyers with tips on how to catch and cook lake whitefish.