HARTSEL — If dependability is among the hallmarks of excellence, pin a gold star on Spinney Mountain Reservoir.
At a time when other producers of large trout stumble through a series of fits and starts, Spinney — old reliable — continues to delight anglers with arm-stretching rainbow trout.
If early angler success, along with Colorado Division of Wildlife net surveys, are indicative, the stretch has been extended a bit this year. Better still, a new stocking strategy is aimed at making it even longer.
“When we took a sample a couple weeks ago, we caught a greater number of fish that were larger than 20 inches,” said Jeff Spohn, DOW’s area biologist.
This measuring stick has assumed a significance that goes beyond the mere mechanics of creel limits. The 20-inch gauge represents a sort of glass ceiling of rainbow growth that has existed since DOW in 2001 began planting 12-inch rainbows in an effort to starve smaller northern pike.
For reasons that continue to confound Spohn, these trout appear to hit the roof a few tiny millimeters shy of that 20-inch mark.
“I’ve tried every tool in the box to find out why this happens,” Spohn said.
His best guess keeps circling back to genetics, the fact that the generic brand of hatchery rainbows chosen for the pike-suppression project simply doesn’t pack enough punch to break the glass.
Spohn is encouraged that a recent infusion of McConaughy-strain rainbows added an extra growth spurt. These fish represent about 18 percent of the total trout population but a greater portion of those over 20 inches.
He’s even more excited about the upcoming October introduction of 45,000 of the Hofer-Harrison Lake cross, a designer blend that could deliver a double knockout.
“The Hofer trout is fast-growing and can get rather large, while the Harrison strain will cause it to run the river more than the generic rainbow we have now,” Spohn said.
This Hofer-Harrison fish brings yet another ray of sunshine. Because this cross is resistant to whirling disease, spawn-run adults could produce surviving progeny in the South Platte River.
Spohn would like to add Snake River cutthroat and rainbow-cutthroat hybrids — both famous for faster growth — to his trout cocktail when hatchery stocks become available.
The biologist also noted that while the pike population remains fairly high, smaller specimens remain in very poor condition.
“There are a lot of stunted pike in the 18-26 inch range that have absolutely no fat on them,” Spohn said. “Most have crayfish, scuds or damselflies in their stomachs, which is the way we like it. We’re not adding trout to their forage base.”
Meanwhile, with prime insect season approaching, anglers must content themselves with a population of rainbows that includes large numbers around 18 or 19 inches.
“These fish are very healthy, and who can complain about a 19-inch fish?” Spohn said.
When a group of Denver anglers surveyed the west end of the lake last week, they found the beginning of the much-anticipated callibaetis hatch, along with the first scurrying of damselfly nymphs toward shore.
Bug activity has been slowed by uncommonly cold water temperature caused by a rapid infusion of snowmelt. The lake now has filled, but the South Platte continues to gush in at more than 400 cubic feet per second, causing the west end to be slightly murky.
When the insect frenzy begins to lure trout to the surface and into the shallows, anglers should find Spinney at its best — or even a little better. Let the arm stretching begin.
Charlie Meyers: 303-954-1609 or cmeyers@denverpost.com
