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Yes we can, do this thing

There was a very upbeat article in the Cour d’Alene Press on Wednesday titled, The Great Kokanee Comeback. The article outlines the apparent success of angling and gillnetting lake trout in recovering an important economic fishery in Lake Pend Oreille. Pend Oreille is similar in many respects to Flathead Lake. Lake trout were planted in the lake in 1925. Opossum Shrimp (Mysis relicta) were introduced by drifting down from Flathead Lake. The largest biomass in the lake is Lake Whitefish. Pend Oreille supports one of the largest lacustrine populations of threatened bull trout in the country. In 1952, Cabinet Gorge Dam cut off 75-80 miles of spawning habitat for native bull trout and cuthtroat trout above the lake. The dam at Albeni Falls, below the lake, began to regulate the lake level, altering some of the best kokanee spawning areas. Beginning in the 1960s, the lake started to see a precipitous decline in their valuable kokanee salmon fishery as well as lower bull trout numbers. Predation by voracious lake trout was named as the primary source of the decline.

“Lake Pend Oreille was one of the best fisheries in the world, with huge numbers of kokanee,” said [Pete] Thompson, who has lived in Sandpoint since 1960. “People came from all over the world to fish here.”

Explosive, exponential population growth was seen in lake trout populations by 2003 with a population doubling every 1.4 years. By the early 1990s, it had become apparent that the kokanee, and bull trout, would disappear entirely without prompt and dramatic intervention. In 2006, fisheries managers began offering bounties to anglers on lake trout and large rainbows. The bounty eventually grew to $15 per fish. They brought in a commercial gillnetting and trapping operation to supplement angling pressure.

As of 2009, the program had begun to show positive results. Survival rates of juvenile kokanee grew from 10% in 2007 to 30% in 2008 and now to 70% in 2009. Hope began to grow that fishermen would be able to once again target the tasty salmon. “We’re keeping our fingers crossed,” said Chip Corsi, IDFG regional supervisor. “If we maintain the survival rates that we have, it’s looking up.Bull trout are showing signs of recovery as well. Redd counts in bull trout spawning streams last fall were up above the 10-year average in most tributaries.

These are all encouraging signs as we begin the process of trying to decide what to do about declining numbers of native fish in Flathead Lake. An exploding lake trout population in Flathead Lake is the number one culprit in the decline of native fish. There are some important differences between Pend Oreille and Flathead that need to be considered however. We too, once had a valuable kokanee salmon fishery that was destroyed by lake trout predation. There is  little hope of recovering our kokanee like they did in Idaho. One of the primary reasons for our kokanee decline was that introduced Mysis shrimp spur the growth and survival of juvenile lake trout, allowing more fish to survive to a size where they prey on kokanee and native fish. Mysis feed near the surface at night and sink to the bottom during the day. Young lake trout feed deep in the lake and kokanee feed near the surface during the day.  Pend Oreille has much higher shrimp densities than Flathead and as lake trout are removed, more shrimp may become available to kokanee.

The goal of removing lake trout in Lake Pend Oreille has been to recover nonnative kokanee salmon, an important economic fishery. While attaining that goal, they have also helped native bull trout and cutthroat trout populations. The goal in Flathead Lake is to specifically recover and restore native fish that are in dramatic decline. While the objectives differ, the experience of Lake Pend Oreille clearly shows that it is indeed possible to recover native fish populations through a strategy that includes recreational angling and supplemental netting. Either method alone is unlikely to achieve our purpose, but in combination, they can show positive results for native fish. The Mack Days fishing event now under way is setting records for killing lake trout, but still falls far short of removing enough predators to benefit native fish. We need to add a targeted, supplemental netting program to remove enough lake trout to allow bull trout and cutthroat trout to survive for future generations.

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