ARIEL — Most years, kokanee fishing at Merwin Reservoir is slow in January, scratchy in February, improving in March and often pretty good by April, especially late April.
This year, it’s like February in April, as anglers on the 4,000-acre reservoir on the North Fork of the Lewis River are fishing hard to catch the landlocked sockeye salmon. And plenty of the fishermen queried at Speelyai Bay boat are reporting zeroes for their day.
Kokanee fishing at Merwin Reservoir is a popular pursuit. Many Saturdays, the parking lot at Speelyai Bay park is full, including the overflow parking area. Kokanee are exceptional table fare.
But catching has been slow — really slow — most of this spring.
Biologists for the Washington Department of Fish and Wildlife and PacificCorp, the utility that operates the three dams on the Lewis River, suspect the dirtier-than-normal water in the North Lewis is the most likely culprit.
Heavy rain in mid-December resulted in huge streamflows coming down the river and through the reservoirs.
Frank Shrier, principal scientist for PacifiCorp, said the inflow to Merwin was so much that the utility spilled water daily from Dec. 6 through 17. During the nine days of Dec. 6 through Dec. 14, the average amount of spill at Merwin Dam was 13,614 cubic feet per second.
The peak day was 19,256 cubic feet per second on Dec. 10.
With high flows comes turbid water. The three reservoirs were brown at year’s end and have been slowly improving to a green.
In early March, Merwin had about 8 to 12 inches of visibility. In early April, the water clarity was perhaps 30 inches.
Most years, anglers can see their offerings many feet deep into the reservoir.
“Turbidity is usually the problem,’’ Shrier said. “With some fish it is because they are sight feeders and can’t see their prey. With kokanee, they tend to just swim with their mouths open and use their gill rakers to sieve out the plankton.
“With high turbidity, sun energy is kept from penetrating the water column which dramatically reduces plankton production — so kokanee don’t do well when that occurs. The odd thing about kokanee is that they do strike at lures. I believe this is a behavioral response and not a feeding response. Nonetheless, if the kokanee can’t see the lures then they aren’t going to strike at them.’’
Aaron Roberts, manager of several Southwest Washington hatcheries including the three on the Lewis River, agreed.
“Turbidity definitely has an effect,’’ Roberts said.
Patrick Linkenheimer, owner of Deadly Venom Tackle in Vancouver, also suspects high turbidity to be the culprit.
His cameras can only see about 6 inches underwater, less than normal.
“Kokanee are attackers,’’ Linkenheimer said. “They do not like stuff. If they can see it, they attack it.’’
Most kokanee anglers at Merwin believe when the reservoir elevation is dropping or rising that it reduces the bite.
U.S. Geological Survey data shows a 6-foot drop in Merwin in late February-early March and a 8-foot rise followed by a 7-foot drop in late March-early April.
There’s also the question if there’s the normal number of kokanee in Merwin Reservoir.
Biologists and hatchery officials agree that when spill occurs at Merwin, some kokanee get flushed downstream.
“Fish spill during high flows, it’s an attraction to them, especially kokanee,’’ said Erik Lesko, a PacifiCorp biologist. “It’s hard to know how many.’’
Merwin also got a reduced release of hatchery-origin kokanee in 2014 and an early release in the summer of 2015 due to warm temperatures and drought conditions, Roberts said.
The goal is to release 93,000 young kokanee split between a March and an October plant.
In 2014, 52,000 healthy kokanee at 6.6 fish per pound were released on March 3, but the fall plant came in mid-September and numbered 25,500 at 19.6 per pound.
“This was an early release and short 15,330 because of disease,’’ Roberts said.
In 2015, 46,360 healthy kokanee at 6.2 per pound were released on March 1. The fall plant came on July 16 and numbered 43,664 at 28.5 per pound.
“They were released early, while still healthy,’’ he said.
Kevin Young, the fish hatchery specialist in charge of Speelyai Hatchery, said “the (2015) program number was met, but they were just smaller in size so that release group may be unphased.’’
John Weinheimer, district fish biologist for the Department of Fish and Wildlife, said an early release is the best choice if there are fish health concerns.
“I’d rather give them a fighting chance than drop dead in the hatchery,’’ he said.
Young said it’s not known whether the March or October releases contribute best to angling success.
“What needs to happen is to differentially mark these groups and conduct creel surveys,’’ he said.
Linkenheimer said the water clarity is improving. He hopes success rates will be better by the time a derby scheduled for May 7 occurs.
Kokanee angling at Merwin has been good for several years, but not so far in 2016, he said.
“It’s just been really, really strange this year.’’
