Kokanee recovery program making progress

SANDPOINT — Biologists and anglers working to recover the kokanee population in Lake Pend Oreille have reasons to be encouraged by progress seen in 2009.

After more than a decade of lake level management to benefit shoreline spawning kokanee, and four years of an aggressive predator reduction program, the kokanee population is showing some very positive signs.

The first encouraging sign came in the fall with the annual population estimates. Each year fishery researchers use hydroacoustics and trawl nets to estimate the population of each age-class of kokanee. The estimates can be compared with previous years to evaluate survival. Although overall abundance was still low, juvenile kokanee survival was the highest seen since 1996.

More than 70 percent of last year’s one-year-old kokanee survived to become two-year-olds this year, accoring to officials. This represents a seven-fold increase from a low of 10 percent survival two years ago.

No one was happier to see those results than Andy Dux, the research biologist charged with monitoring the population.

“Last year we saw an increase from 10 percentsurvival to 30 percent survival, and we were pleased with that, so to see it more than double this year, is really exciting,” Dux said.

More good news came later in the fall during the kokanee spawning season. Each year a trap is set up in Granite Creek to collect kokanee returning to spawn. Eggs are stripped from many of the fish. The resulting offspring are raised in Cabinet Gorge Hatchery and later released into the lake.

Typically, 10-15 million eggs are collected each year at the trap. In the past two years, however, it’s been nowhere close to that, with just over one million eggs taken between both years combined.

“Although the hatchery is not the key to recovery of the Pend Oreille fishery, it represents one very important component,” Jim Fredericks, regional fishery manager. “Getting 8.25 million eggs is a real boost this year.”

According to Fredericks, the juvenile survival rates and the increased number of kokanee spawners are solid evidence the efforts to reduce predators are paying off. Since 2006, Fish & Game has used a two-pronged approach consisting of netting and harvest incentives to reduce the number of lake trout and rainbow trout.

Mitigation funds from Avista and BPA are used to contract commercial netters from Lake Michigan to help control the expanding lake trout population. Their specialized equipment and decades of experience netting deepwater lakes make them uniquely qualified to work on Pend Oreille. To date, they’ve removed nearly 40,000 lake trout.

Avista mitigation funds are also used to fund the Angler Incentive Program, which pays anglers $15 for each lake trout and rainbow trout harvested from Lake Pend Oreille. Since 2006 anglers have turned in nearly 50,000 lake trout and 25,000 rainbow trout. According to Fredericks, anglers have been extremely valuable in this effort.

They’ve removed a lot of lake trout, but they’ve also removed a lot of rainbow trout. The nets don’t capture rainbow trout, so the angler catch is critical to the success of the predator control program.”

Although the Pend Oreille fishery recovery effort has not been without controversy, Fredericks said the one thing nearly all Pend Oreille anglers agree on is that kokanee are the key to restoring a healthy fishery.

“Not only do they provide a popular fishery, they are the foundation for the world famous trophy rainbow fishery as well,” he added. “Kokanee are also essential to a healthy bull trout population, so everyone ought to be pretty excited with what we saw in 2009.”

While the biologists are confident in saying the increased survival rates are a direct result of decreasing the number of predators in the lake, they’re quick to point out that predator removal is not the whole key to recovery in Pend Oreille.

“Although many may think the Pend Oreille fishery recovery effort is all about the commercial netting and harvest reward programs, the effort really began with, and still relies on, lake level management,” Dux said.

Research in the early 1990s demonstrated a full 11.5-foot winter drawdown on Pend Oreille left the best kokanee spawning gravel high and dry, and that the loss of those important spawning gravels was a big reason the kokanee population had been in decline since the 1960s.

As a result of the research and the importance of kokanee to the Pend Oreille bull trout population, the U.S. Army Corps of Engineers has kept the lake at a higher level (7.5-foot drawdown) the majority of years since 1996. Modifying winter lake level management has more than doubled the survival of kokanee eggs to fry in the wild. Because wild kokanee production drives the fishery, maintaining high survival rates for all ages of kokanee – including eggs – is critical to recovery of the fishery.

The decision on extent of drawdown is based on several factors including precipitation forecast, previous year elevation, and the number of wild kokanee spawners expected to use the shoreline. Periodically lowering the lake can actually benefit kokanee by allowing winter wave activity to redistribute and clean the shoreline gravels, as is the case this year.

According to Dux, the predator problem began developing in the late 1990s — just as the solution to the spawning habitat problem was being implemented.

“Juvenile survival is the big bottleneck in the population right now, but as we get more kokanee surviving to adulthood, it’s critical that we continue to manage the lake to provide ample spawning habitat that will allow the population to completely rebuild”.