The impact of last winter’s floods on trout in North Idaho’s cutthroat streams ranged from temporary inconveniences to a long-term catastrophic loss, one of Idaho’s top fish managers says.
Ned Horner, Panhandle fisheries manager for the Idaho Fish and Game Department, said fisheries officials won’t know the extent of the flooding impacts for several months.
The upper St. Joe was not damaged nearly as much as the lower river and much of the Coeur d’Alene River, he predicts.
Fisheries at North Idaho’s large lakes should be status quo this season, Horner said:
Lake Pend Oreille fishing will be similar to last year. Kokanee numbers won’t increase until a higher lake level is maintained through winter.
Priest Lake mackinaw should average 19 inches. Although a fair number of larger fish inhabit the lake, no increase in the average length is expected until anglers agree on a different management program.
Lake Coeur d’Alene should produce as many chinook salmon as last year despite the flooding.
However, flooding that wiped out a dike likely will dampen rainbow and cutthroat trout fishing at Hayden Lake for at least three years.
The hatchery rainbows and cutthroats stocked in Jewel, a specially managed lake, will be 10 to 16 inches long, not to mention a few 5- to 6-pound broodstock trout.
Horner said there were two major floods last winter in North Idaho, “a high elevation event in early December and the more intense and widespread low elevation event in February.”
The February flood occurred while fish were locked into their over-wintering areas, Horner said.
“Eggs of fall spawners were incubating in the gravel, small fish were tucked into the cracks between rocks or along the bank in the brush and adult fish were concentrated in large, deep, slow-moving pools.”
He said fall spawners such as bull, brook and brown trout, chinook salmon and mountain whitefish were hit hard.
“Many streams experienced significant movement of the stream bottom gravel,” he said. “Eggs of fall spawners and young trout of all species were easily killed by the shifting gravel. The fine sediment created muddy water that temporarily prevented fish from feeding effectively, killed aquatic insects, smothered eggs buried in the gravel.
“Stream-dwelling fish can usually escape fast water by holding close to the banks, but ice jams and debris torrents can literally grind fish up as they rumble downstream.”
Most worrisome, he said, is the long-term habitat destruction caused by destabilized streams. Biologists expect to see further declines in fish populations in drainages where habitat was already impacted by past land management activities. They think there will be little impact in drainages that are not roaded and only lightly developed.
Overall, impact of floods along the upper St. Joe was minimal, compared to the impact along the Coeur d’Alene River and the St. Joe below Slate Creek, he said. There was “significant damage” along the Little North Fork of the Coeur d’Alene.
Horner said rainbows aren’t as plentiful in Lake Pend Oreille as they were in the early 1990s and fishermen “aren’t happy” about the situation. If rainbow numbers are to be increased, he said, the kokanee population must be boosted.
However, that’s not possible as long as the Bonneville Power Administration annually draws down the lake so low that gravel where kokanee eggs have been deposited are exposed.
The Fish and Game Department will release 50,000 chinooks into Lake Coeur d’Alene in June, an increase of 20,000 over the previously planned release to compensate for eggs lost to floods, Horner said.
, DataTimes MEMO: This sidebar appeared with the story: Kokanee watch Look for big kokanee in small North Idaho lakes this year. Stocking numbers have been reduced at Brush, Smith, Hauser, Lower Twin and Mirror lakes, but the silvers could range up to 22 inches long.