Lake trout netting program boosts kokanee survival

SANDPOINT — Angler harvest of rainbow trout remains a high priority for the Idaho Department of Fish & Game as fishery recovery efforts continue on Lake Pend Oreille.

Netting from March to June has removed more than 10,000 lake trout, according to a recovery update report prepared by Panhandle Fisheries Manager Jim Fredericks and Andy Dux, principal fishery research biologist.

The netting, however, is not targeting or removing significant numbers of rainbow, “so the recovery effort depends entirely on anglers to reduce the rainbow population,” the report said.

Only 33 rainbows were caught in gill and trap nets this spring and summer, the report said.

Fish & Game upped the stakes in its incentive program this year to encourage rainbow trout harvest. Nearly 100 rainbow trout were implanted with passive integrated transponder tags that have been assigned cash values ranging from $50 to $1,000.

“To date, two anglers have received $500 checks in addition to the standard $15 incentive payment,” the report pointed out.

But angler harvest of both rainbow and lake trout are down sharply from last year’s levels.

More than 13,000 lakers were harvested in 2008, compared to just 5,300 in 2009, the update indicates. Anglers harvested nearly 4,700 rainbow trout in 2008, but that figure slipped to barely 2,700 this year.

The incentive program has also led to the accidental harvest of 50 endangered bull trout by anglers who mistook them for lake trout, the report noted. In 2009, 435 bull trout turned up in trap and gill nets, but only 88 were removed.

Since launching the netting and incentive programs in 2006, nearly 80,000 lake trout and more than 20,000 rainbows have been removed from the lake. Fish & Game seeks to weaken rainbow and Mackinaw populations on a short-term basis to ease predation on kokanee.

“There’s little question, based on both netting and angler reports, that the lake trout removal effort has greatly reduced the number of older, larger, lake trout resulting in a much smaller average size. That’s good news,” the report concluded.

Annual trawl and hydroacoustic surveys used to gauge the size of the kokanee population indicated an increase in kokanee abundance and survival for the second year in a row.

Particularly encouraging, the report said, was the survival rates for juvenile kokanee in the one- to two-year age class. In 2007, juvenile survival dropped to a dismal 10 percent, a rate that would have led kokanee collapse if nothing was done to correct the slide.

The juvenile kokanee survival rate improved to 30 percent last year and this year is estimated to be up to 67 percent, the report said.