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Lake Nighthorse kokanee salmon help ensure next year’s stock

The 150,000 fish released into the reservoir will produce up to 1.5 million eggs this year
Kokanee salmon are a landlocked version of the sockeye species native to the northern Pacific Ocean. (Jerry McBride/Durango Herald)

A persistent breeze off the chilled waters of the Lake Nighthorse reservoir made for contemptibly cold conditions on the small floating platform where Colorado Parks and Wildlife biologist Jim White and his small cadre of helpers work two days per week for a month each fall. On Nov. 4, five men worked aboard the platform, each clad in bright rubber fishing gear.

Free fish

Kokanee salmon will be given away about 2 p.m. Friday, Nov. 18, in the parking lot at Lake Nighthorse. Participants of the giveaway must hold a valid Colorado fishing license. Youths up to age 4 may receive kokanee if accompanied by a license-holding adult.

The team’s work is methodical, nearly mechanized, and appears almost too simple given the great importance it carries. One CPW employee scoops a dip-net full of kokanee salmon out of a mesh enclosure suspended in the lake within the center of the platform. He dumps the fish into an bath-sized tub of water, where reduced oxygen levels lull the vivacious fish to into a semi-sedated state.

Then, two men – White and his now-retired predecessor, Mike Japhet – alternate grabbing male and female fish, carefully aim the hole in the rear of the abdomen into the small plastic tubs in front of them, and squeeze. Most of the fish release a satisfying “splat” as their reproductive material, either spawn (eggs) or milt (sperm), shoots into the tub.

Conversations on the platform are interrupted by the regular cry of “got one” from the biologists handling fish each time they spawn a female salmon.

Colorado Parks and Wildlife officials and volunteers work on a floating platform just off shore. The platform has nets suspended underneath it to trap and contain the fish. (Jerry McBride/Durango Herald)

The biologists can often tell if a fish is “ripe,” meaning ready to spawn, before they squeeze. If the fish is not ripe, it gets tossed back into the water to be spawned next week. If it is ripe, it gets tossed into a separate pen to be given away to the public later in the day.

“Think like bananas,” Japhet said. “If bananas aren’t ripe, we don’t eat them.”

As the historic Colorado River Basin drought and a warming climate continues to alter the habitat of kokanee salmon, the spawning that CPW performs at Lake Nighthorse each year grows increasingly important.

The species was first introduced in Colorado in 1951. Kokanee salmon are nearly identical to the sockeye found in the northern Pacific Ocean. Sockeye are anadromous, meaning they live most of their lives in saltwater but return to freshwater to reproduce. Unlike their anadromous relatives, kokanee salmon are landlocked and spend their entire lives in freshwater. Although they are nonnative to the region, they thrive in the cold water of Colorado’s lakes and reservoirs.

“We’re primarily doing this to provide sport fishing opportunities all over the state,” White said. “... Not only will anglers benefit by catching them, but folks who like fishing for trophy lake trout (will benefit) because kokanee are a good prey fish for trophy lake trout.”

White said that kokanee are not only fun to catch and a nutritious meal for trophy lake trout, but they are healthy eating for humans as well because they eat plankton, and thus do not accumulate mercury. He also said the salmon will not eat or crossbreed with native fish species.

As of this year, CPW stocks 26 lakes and reservoirs with baby “fingerling” kokanee each spring. Next year, CPW hopes to have 10.2 million eggs with which to hatch kokanee to stock Colorado’s waters.

Kokanee salmon eggs are fertilized, then washed and sterilized. They expand and harden in the first 30 minutes of their life, after which time they can be moved without risk of breaking. (Jerry McBride/Durango Herald)
After kokanee salmon eggs and milt, a seminal fluid, are collected from the spawning fish, the fish are given away by Colorado Parks and Wildlife to the public. (Jerry McBride/Durango Herald)

After Japhet and White mix the salmon’s reproductive material, a fourth CPW employee rinses the eggs in a water bath. It takes just a minute or so for the eggs to become fertilized. They are then soaked in an iodine bath to disinfect them and prevent the spread of any viruses.

After 30 minutes in iodine, the eggs have swollen up and hardened, allowing CPW officials to move them.

“Once 30 minutes goes by, then we can put the eggs in those big coolers and then transport them,” White said. “We have about eight to 10 hours to get them where we need to get them before they need to be put out (in hatchery trays). At that point, they really can’t be messed with for about another 40 days.”

White and his team will spawn somewhere between 1 million and 1.5 million eggs from Lake Nighthorse’s kokanee population this year. Most of those eggs are taken to the Roaring Judy Fish Hatchery located upstream of the Blue Mesa Reservoir, near Gunnison, where CPW biologists will monitor them until they are fish roughly 2 inches in length.

Jim White, Colorado Parks and Wildlife aquatic biologist, squeezes eggs from a kokanee salmon on Nov. 4, at Lake Nighthorse. (Jerry McBride/Durango Herald)
Kokanee salmon eggs are collected by Colorado Parks and Wildlife on Nov. 4 at Lake Nighthorse. (Jerry McBride/Durango Herald)

“We only stock about 150,000 kokanee in (Lake Nighthorse),” White said. “So it’s a pretty good return for the number of fish we stock.”

There are 13 bodies of water in Southwest Colorado that will be stocked with fingerling kokanee in the spring, which will require CPW to procure almost 4.9 million fish. Of those 13 bodies of water, five are considered “brood lakes” like Nighthorse, where CPW biologists take eggs to raise for the next year’s stock. The 150,000 kokanee stocked in Nighthorse produce 20% to 30% of the total fish needed next spring in Southwest Colorado.

The Vallecito Reservoir used be a wealth of kokanee spawn, but White said CPW gave up on the lake eight years ago. CPW spokesman John Livingston called the lake “no longer viable.”

“When you get really low reservoir elevations from drought years, it’s just not good for kokanee,” White said. “It gets too warm, and where it’s cold, there’s not enough oxygen to support them. And where there’s oxygen, it’s too warm. So they get what’s called ‘squeezed.’”

White said an influx of mysis shrimp and gill lice have reduced the productivity of the Blue Mesa reservoir. Increased water usage or changing conditions could also threaten productivity of Lake Nighthorse or McPhee Reservoir in Dolores, both of which are important sources of kokanee eggs, meaning CPW tries to maintain all five brood stocks to avoid putting all its eggs in one basket.

Jim White, Colorado Parks and Wildlife aquatic biologist, takes a boat from the dock at Lake Nighthorse on Nov. 4, out to the platform where spawning kokanee salmon have gathered in a fish trap so that staff members and volunteers can collect eggs from the fish. (Jerry McBride/Durango Herald)
The line for the first kokanee salmon giveaway of the year at Lake Nighthorse began to form over an hour before the event’s start time. Anyone with a valid Colorado fishing license is eligible to receive free fish. (Jerry McBride/Durango Herald)

By 2 p.m., White and his team had handled 1,650 fish. Those salmon, which are just 9 to 11 inches long as a result of cold conditions in Lake Nighthorse that limit growth of the plankton the fish feed on, were contained within one pen. Salmon die after they spawn, and those that are spawned in Lake Nighthorse are no different.

To avoid both wasting the meat and the foul nuisance that thousands of decomposing salmon carcasses create, CPW gives away the live fish after spawning them. A line beginning at the water’s edge grew steadily as the biologists finished their work and towed the pen over to the boat ramp. Anyone with a Colorado fishing license is eligible to receive salmon.

Adam Dalrymple said the kokanee salmon are a staple of his household’s winter food supply. He, his partner and their daughter eat the fish about once per week all winter.

“If we don’t get a deer, I’m always here,” he said. “And then we are here if I have time if we do (get a deer).”

Dalrymple said about 50% of his household’s diet is from food they are able to harvest themselves.

“It’s a joy – it’s a part of why I live here,” he said.


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