Taking heart over the hatch
The hatch is on.
The annual outburst of bugs commonly called mayflies, actually caddis flies, is hitting area rivers and windshields.
For motorists stuck with the chore of washing bug splat off their cars and recreationists who must wave away the little beasties along local river trails, this annual rite of spring may be little more than a nuisance.
But it also kicks off the summer fly-fishing season in a dramatic and welcome fashion. And besides providing an economic boon for fishing guides and shops – not to mention area carwashes – it’s welcome from an environmental standpoint as well.
“As far as the river ecosystem goes, it’s a very beneficial and natural process that happens annually,” said Rick Lofaro, water quality coordinator for the Roaring Fork Conservancy, a local nonprofit river advocacy organization.
Colorado Mountain College biology professor Bob Kelley said the river-based caddis flies “are food for a lot of organisms. They’re part of the whole balance of the riparian zone.”
“It’s kind of a neat thing,” he said of the annual early-May hatch, “and it’s kind of reassuring to see it happen every year. Everyone talks about lots of changes, but some things are kind of reassuring for old people like me.”
“It is reassuring,” Lofaro agreed. “Something would be likely awry if the caddis flies weren’t hatching.”
Aquatic insects “are really the canaries in the coal mine of the river,” he said. The variety and quantity of these insects are good indicators of water quality, and declines would be cause for alarm.
Lofaro, an avid fisherman, is happy to report that the conservancy, which samples water quality at 23 sites every month, has found area rivers to be healthy.
“Overall we’re in good shape. We have a few areas of concern that we’re monitoring more, but as a general rule what we have found is our water quality is in good shape,” he said.
Kelley, who grew up in Glenwood Springs, said the caddis fly hatch has been an annual and unchanging tradition. He remembers watching clouds of caddis flies swarm off the Roaring Fork River when he was a student at Glenwood Springs Elementary School downtown.
“There’s always been this hatch the first of May and everyone’s called them mayflies because they come out in May,” he said.
To get technical, neither mayflies nor caddis flies are really flies at all, said Kelley. True flies have one pair of membranous wings, and caddis flies have two pair, he said.
This may be far more than many people want to know about caddis flies.
But they can take comfort knowing the big hatch happens as surely as the rivers run high in May and June, the aspen turn gold in September and ridgetops get dusted with snow by October.
A visitor to the valley might think we’ve got a bug problem. But the caddis fly hatch is short-lived in any one area, as it works its way up the valley from Rifle to Aspen as warm weather reaches higher elevations.
Caddis flies are also short-lived, at least in the final, winged stage of life.
So if you’re feeling bad about the number of caddis flies your car is sending to an early death on your daily commute, rest easy.
“They mate, lay their eggs, and then they die,” said Colin Taylor, a guide at Roaring Fork Anglers in Glenwood Springs. “It’s just wake up, have sex and die. That’s pretty much how it works.”
Caddis flies spend most of their lives – about a year – underwater, in a larval stage, living in a casing Taylor called a “shuck.”
Said Kelley, “They are kind of neat. They live in little houses in the stream.”
The emergence of caddis flies from the water is the first of the predominant area river hatches each season, said Taylor.
“It’s a really big hatch,” he said. “This hatch is the true spark for the dry fly fishing for the summer.”
He said the insects’ numbers usually peak around 3 or 3:30 p.m. each afternoon.
“You see thousands and thousands of the flies coming off” the water, he said.
Anticipated hatches of certain other aquatic insects haven’t happened this year, he said.
“Sometimes it happens, sometimes it doesn’t. Some years are better than others,” Taylor said.
Not so with the caddis flies.
“The caddis hatch can be almost guaranteed to be very good every year. There’s just millions of millions of caddis flies in the river,” Taylor said.
Another major hatch of the year is green drakes, which usually emerge in June after the spring runoff subsides. It could happen earlier this year because runoff is expected to be low, Taylor said.
Anglers like to get out on the rivers during these hatches because the fish are sure to be biting. Taylor said it’s best to fish waters where the insect activity is lighter. Where a hatch is heavy, an angler’s fly competes with too many insects for the fish’s attention.
“They’ll take the natural fly over the artificial fly,” Taylor said of the fish.
The emergence of caddis flies is a welcome time, from a fish’s perspective.
“It means that it’s spring, we get to eat, finally,” said Taylor.
Fish are less active when it’s colder. The emerging insects provide for a big, badly needed feeding fest.
The hatch is especially important for rainbow trout, which have just exerted a lot of energy fertilizing and laying eggs during the spring spawning season, he said.
Females lose a lot of weight when spawning, and start to regain it now.
While the fish will take some of the caddis flies as the insects fly above the water, 80 percent of a fish’s feeding actually occurs underwater, Taylor said.
Kelley noted that hatches are important not only for fish but for birds, which have high demands for food this time of year because they are nesting.
Taylor isn’t too worried about the local availability of aquatic insects for fish in the future.
“There’s always going to be food availability. It’s just a very, very lush ecosystem here. There’s an enormous amount of insects.”
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Grace Wesseling is an animal lover, a cheerleader of seven years and another soon-to-be graduate of Bridges High School, class of 2021.