Aerial Fish Stockings in Colorado

Colorado Parks and Wildlife will stock nearly 275,000 fish into 240 mountain lakes this 2021 summer. Tag along on this mid-August day as cutthroat trout are getting a lift up to Colorado's alpine lakes!
Video: Aerial Fish Stockings in Colorado

Staff from the Rifle Falls State Fish Hatchery and pilots for Colorado Parks and Wildlife stocked cutthroat trout by airplane in Colorado’s high mountain lakes on Monday and Tuesday. 

It was the second of three aerial stocking rounds taking place this summer. It is a part of CPW’s annual operation for managing its alpine lakes for the future enjoyment of the public. 

It is also efficient. Years ago, these lakes would get stocked by loading fish into milk cans and hiking them up on horseback to get into the remote areas. Without the use of the airplanes, not nearly as many lakes would receive fish.

“Our aerial stocking program is critical in our efforts to provide high mountain lake angling opportunities throughout Colorado,” said Josh Nehring, CPW’s Assistant Aquatics Section Manager. “Most of these remote high mountain lakes do not have the proper habitat and conditions to allow for natural reproduction. Over the course of just a couple of weeks, CPW stocks hundreds of lakes each year using this method.”

Three CPW pilots in their Cessna 185 Aircraft airlifted one-inch long nanitas cutthroat trout to their new home in Colorado’s pristine high-elevation lakes Monday and Tuesday. 

Over 95,000 of the cutthroat trout were stocked into 73 lakes those days by wildlife pilots Denise Corcoran, Larry Gepfert and Steve Waters. Back in late July, the Rifle Falls Hatchery produced nearly 37,000 Colorado River cutthroat trout that went into 64 lakes via same-day air delivery.

The one remaining aerial stocking operation on this summer’s slate will occur in September when native cutthroat trout, golden trout and arctic grayling reared at the Mt. Shavano State Fish Hatchery will go out.

In total, CPW will stock nearly 275,000 fish into 240 lakes this summer. Nearly all of the lakes stocked are in the southern half of our state’s mountainous region. Next year, the aerial effort will focus on the alpine lakes in the northern half, part of CPW’s sky stocking rotation regime.

Meridian Lake | Gunnison County | 9,626 feet in elevation

On the hatchery side, there is some precision that goes into coordinating when the fish will go out via airplane. 

“We have a short window to grow the fish big enough to get on the airplanes,” said Bryan Johnson, Mt. Shavano Hatchery Manager. “We get our eggs for the aerial stockings towards the end of June and they have to be out by October before they get too big. Our window is typically right after Labor Day weekend and from there we only have a couple of weeks before the winds get bad or the weather starts turning. We’ve been doing this for a number of years now, so it is pretty easy to look back at previous flight plans to schedule it all out with our pilots.”

Once stocked via air delivery, it will take these fish a year-and-a-half or two years to grow to a catchable size of 10 inches. There definitely is a niche among anglers who enjoy a nice hike up to fish these pristine waters in the high country. Among the lakes stocked on Monday, the highest of them – Ptarmigan Lake in Gunnison County – sits at 12,306 feet. Nineteen of the 24 lakes shown in the video sit above 10,000 feet in elevation and they really showcases the beauty of Colorado’s high country.

Bonita Reservoir | Delta County | 10,010 feet in elevation
Bonita Reservoir | Delta County | 10,010 feet in elevation

And the fish, well they just float on down once deployed from the airplane. The pilots slide down into the site and slow the plane down to roughly 85-90 miles per hour before releasing the fish. 

“We’re about 100 feet above the lake and as we’re coming across and as they dump, they almost stop immediately as they come out of the airplane,” Gepfert said, who is approaching 20 years as a pilot for CPW. “They are very tiny, the fish today were about one-inch in size. Their heads are heavier and so they tend to elongate vertically and drop with the water and then they just go into the lake. They did studies years ago and the survival rates are in the 90 percentile. 

“They just have very little mass to them so they are just kind of floating down into the water.”

This second round of stockings on Monday and Tuesday planted fish into lakes in Delta and Gunnison counties. The July aerial stockings also dropped fish into lakes in Gunnison, Hinsdale, Mineral, Pitkin, San Juan and San Miguel counties.

“The hatcheries are a big part of it, we’re kind of just the final step in the process in getting those fish out there,” Gepfert said. “There is a lot of time spent growing those fish and planning all of this by a lot of people involved. This is the final phase of getting them out there for the anglers.”


Video and article by Jason Clay. Jason is a public information officer for the Colorado Parks and Wildlife northeast region.

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