VALLECITO

Six abreast, dressed in waders and waterproof jackets, a team from Colorado Parks and Wildlife waded up Grimes Creek splashing with long-handled fish nets to drive kokanee salmon into a wire-mesh cage.

The trapped kokanee will provide eggs for the Colorado Parks and Wildlife hatchery in Durango. In the spring, 2-inch kokanee fingerlings will be stocked in the reservoir here, Grimes Creek and Lake Nighthorse to start the cycle of life again.

Ninety percent of eggs introduced into the hatchery runways survive. The kokanee reaches sexual maturity in three to four years.

“We’ve been doing this for 45 years,” said Jim White, the Colorado Parks and Wildlife fish biologist in charge of the kokanee capture. “Kokanee can spawn and survive naturally, but the eggs tend not to survive in cold water.”

Collecting eggs Thursday at the “kokanee corral” set up in Grimes Creek, a tributary at the north end of the reservoir, were White, hatchery fish culturist Sarah Bashaw, hatchery temporary employees Pete Deren and Graham Mytton, longtime volunteer Willy Reynolds and Mike Japhet, who held White’s job for many years but now, in retirement, works at the agency from time to time.

As thrashing kokanee in the cage turned the water to froth, the team members began the process of stripping them of their reproductive assets.

Standing knee-deep in the low-40-degree water, they worked rhythmically. Each would pull a kokanee from the wire-mesh cage, squeeze out its milt (sperm) or spawn (eggs) into a plastic cup and toss the spent fish into another cage.

Male kokanee are distinguished from the female by an upturned tip on the lower jaw (called a hooked jaw), a slightly humped back and more color.

Every few minutes, fertilized eggs – they become impregnated within seconds – are washed clean of milt and placed in a 19 percent iodine solution for 30 minutes to be disinfected and to harden.

The eggs will rupture if they’re moved before they harden.

The estimated 1,000 kokanee milked Thursday would remain in their watery cages overnight to be given away free Friday at the community center here to holders of a Colorado fishing license.

Kokanee, a member of the trout family, is native to the Northwest and Alaska, but they’re stocked in Colorado and other states as a favorite game fish.

Kokanee feed only on plankton, with their growth dependent on the size of the fish population and the availability of food.

Earlier in the morning, White visited the northeast shore of the reservoir to inspect a Merwin net, a floating platform tethered about 50 feet from shore.

The platform supports submerged nets to hold captured kokanee. Kokanee, which prefer the open water most of the year, move along the shore at spawning time looking for a stream.

If they attempt to pass the Merwin net between the platform and the shore, a nylon-mesh curtain suspended on buoys and reaching the lake bottom blocks their path.

Looking for a way around the curtain, kokanee swim into a maze of netting of ever-diminishing size that funnels them into the holding area under the platform.

“We’re testing the system here, but so far we’re not getting good results,” White said.

The number of kokanee in the nets didn’t warrant setting up the sperm/egg extracting process, he said.

“The Merwin net was bought for use at Lake Nighthorse where there are no inflowing streams and the kokanee circle the shore,” White said. “You may see it there someday.”

Kokanee don’t spawn in a lake, White said. They need flowing water and a bed of gravel.

White regularly extracts eggs and sperm from McPhee Reservoir kokanee that spawn about six miles north in the Dolores River.

This year was an exception, he said, because the low water level in the reservoir didn’t produce enough salmon to make the effort worthwhile.

Kokanee die after spawning. If they die in their home stream, the decaying flesh adds nutrients to the stream and the reservoir, White said.

He doesn’t bother with kokanee in Vallecito Creek, which empties into the reservoir on the north shore, White said.

“It’s too hard to capture them because after the Missionary Ridge Fire, the creek was split into two channels,” White said.

daler@durangoherald.com