Spawning space for kokanee will be kept at a minimum this fall in northern Idaho's Lake Pend Oreille because little space is needed; only 40,000 mature females are expected to deposit eggs in the lake bottom gravels this year.

But signs point to improving status of the lake's depressed kokanee population. An aggressive effort to remove from the lake fish – primarily lake trout – that prey on juvenile kokanee may be paying dividends. Survival of younger kokanee has vastly improved during the past two years, which should translate to higher numbers of adult fish in the future.

"Hopefully we can start a rebuilding trend," Russ Kiefer told the Technical Management Team Wednesday. Kiefer represents the state of Idaho at TMT, which is made up of federal, state and tribal fish and hydro system officials. They mull day-to-day hydro operations that might be implemented to benefit fish.

A spawning population of 40,000 females would be better than the 22,000-fish total in 2008 and the low ebb of 5,000 in 2007. But it is well below levels of the 1990s and earlier for a stock that was once one of the lake's most prized fishery. Up until the mid-1960s annual harvests of more than 1 million kokanee were common. The harvest of kokanee has not been allowed since 2000 because of low numbers.

State officials say that deep wintertime drawdowns of the lake, which began in the mid-1960s, resulted in a declining trend in kokanee fry survival and in the overall population. The lake level is controlled by a U.S. Army Corps of Engineers hydro project, Albeni Falls Dam.

Changed operations that began in 1996 seemed to arrest the decline, but the beleaguered landlocked salmon population then became victim of the huge lake trout and Gerrard rainbow that roam the lake. The lake trout population in 1999 started to grow exponentially, feeding heavily on the juvenile kokanee population.

Since 2000 predation has been considered the primary factor limiting the kokanee population, surpassing spawning habitat limitations.

The state in 2006 triggered a two-pronged attack on the lake trout and a one-pronged attack on the Gerrard rainbows. Beginning in May of that year a $15 bounty was offered for lake trout of any size and any rainbow 13 inches or larger. And commercial fishers were hired to focus on the lake trout.

The lake trout, Gerrard rainbows and kokanee were all introduced to the lake with kokanee and the rainbows being the favored target of most fishers. Kokanee provide the added benefit of being a favored foodstuff of native bull trout, which are listed as threatened under the Endangered Species Act.

The lack of kokanee puts the bull trout at risk, according to state and U.S. Fish and Wildlife officials. The USFWS is charged with restoring the vitality of the listed bull trout.

From May 2006 through July 2009 Lake Pend Oreille anglers cashed in on 46,000 landed lake trout. The commercial fishers – using gill-nets and trap nets -- caught another 33,000 during that period. Overall, the Idaho Department of Fish and Game estimates that the lake trout population has been falling at a rate of 58.5 percent per year since the removal programs were started.

Gill-netting in 2008 at the favored lake trout spawning grounds pulled in an estimated 74 percent of the total adult population in the lake.

The programs are costly, $435,000 per year for the commercial netting and up to $500,000 for the angler incentive program (the high payout is $387,000). Most of the funding comes from the Bonneville Power Administration and Avista Corporation as mitigation for the operation of, respectively, Albeni Falls and Cabinet Gorge dams.

IDFG officials feel that it is more than a coincidence that the lake trout's fall is being mirrored by increase in juvenile kokanee survival. Survival from age 1 to age 2 jumped from a low of 10 percent in 2007 to 32 percent in 2008 to 77 percent this year, "which is phenomenal," said the IDFG's Andy Dux, principal fishery research biologist.

Survival from age 2 to age 3 rose from 4 percent in 2007 to 40 percent in 2008 to 59 percent this year. Most kokanee spawn at age 3 or 4. Dux cautioned that all of the 2009 data is preliminary.

"We've also had survival increases in our other age classes," Dux said. Largely credited are those "efforts to reduce predation pressure."

Dux said he was encouraged, "but we've still got a lot of work to do."

The commercial removal has gained focus with the help of so-called "Judas" fish, mature lake trout that have been implanted with radio transmitters during the last three years. The tagged fish helped lead the gill-netters to the two major lake trout spawning areas in the lake and resulted in last year's huge reduction in the adult lake trout population.

"Those are the ones that have the potential for eating the most kokanee," Dux said of the adult fish.

"Now we've gotten to the point that we've trapped enough fish that abundance is getting lower," Dux said. The commercial fishers are likely to find the fishing tougher this fall at the spawning grounds.

Another likely result of the lower abundance is that, during the 2009 spring season, seven deepwater trap nets trapped only 56 percent of the number of fish they had trapped in 2008.

Through the use of hydroacoustics (sonar) and trawl surveys state officials were able to identify habitat on the north end of the large lake that is heavily used by the subadults.

This spring smaller mesh gill-nets were used to sweep those north shore areas. The result was that 11,331 lake trout, most of which were subadults, were netted. That nearly matched the total of 11,761 for all of 2008. The netting is conducted for about three months in the spring and three months in the fall through the spawning season.

There's a phenomenon in nature called compensation in which a depleted population, such as the shrinking lake trout stock, can react by, as an example, producing more eggs or growing and maturing faster to rebuild. But it's not likely to happen with a reduction well over 50 percent, and growing.

"There's no way they're going to get over that," Dux said.

Ideally the lake trout would be eradicated.

"Lake trout are kind of a bad neighbor that we want to go away," Dux said.

The Gerrard rainbow trout on the other hand are a highly prized fishing target. The IDFG would like to get rid of the lake trout, and reduce the Gerrard population for now to allow the kokanee to rebound.

The rainbows have been able to avoid the nets because of their lifestyle. The lake trout tend to hug the shoreline and swim deep while the rainbows float around in open water offshore.

"We really can't target them with nets," Dux said.

Despite precautions, bull trout are occasional victims. A total of 200 died for the cause last year out of 1,000 that became trapped in the nets. But they are expected to be among the biggest beneficiaries if the kokanee population rebounds.

Dam operations remain a key part of the kokanee recovery strategy. The IDFG and USFWS on Wednesday asked the Corps to begin drawing down Lake Pend Oreille from an elevation of 2,060 to 2,051 by Nov. 15. That's when the kokanee spawning season is expected to begin.

Under the kokanee operational strategy the lake leveled is maintained through the fall and winter at an elevation no lower than a certain level each year ranging from 2,051 to 2,055. The preference is to hold the level at a higher elevation in most years and occasionally drop the elevation so that wave action can wash fine sediments from the gravelly near-shore area that kokanee prefer. The higher levels allow access to a larger area of near-shore gravels.

The "system operations request" submitted this week to TMT by the IDFG and USFWS said that the lower level this year would provide "adequate spawning gravel for this low female abundance at elevation 2,051."

The prespawn drawdown is needed so that kokanee don't spawn at higher elevations and then have the nests dewatered.

A relatively prolonged drawdown will allow the water to be evacuated at flows that won't cause problems downstream, such as forcing Box Canyon Dam to spill water above its turbine capacity and create total dissolved gas in the Pend Oreille River.

And, with below normal precipitation forecast for November through October, the additional flows from Pend Oreille "may help provide river flows below Bonneville Dam that are more advantageous for chum salmon spawning before increased flows from winter flood control drafts at upstream reservoirs arrive," the SOR says. Flows are regulated below the lower Columbia River's Bonneville Dam to allow chum access to spawning sites and to maintain a water cover for their eggs. Chum are listed under the Endangered Sepcies Act.

The TMT members approved the request unanimously.