Sunday, May 30, 2021 | 2 a.m.
LAUGHLIN — Decades of human interference led to an explosion of the caddisfly population in the short stretch of Colorado River running alongside Laughlin.
Now, a relatively simple manipulation of one of the main culprits of the surge could bring the nuisance insects down to manageable levels, and not a moment too soon for long-suffering locals.
The Bureau of Reclamation is reducing the flows from upstream Davis Dam over seven days in May and June to expose the eggs and larvae of the small, moth-like insects that speckle, swarm and outright blanket the businesses, homes, boats and people closest to the river banks in Laughlin and its Arizona sister town, Bullhead City.
“The numbers are so overwhelming in some spots that they just reduce the quality of life for people that live on the river and people that want to use the river for recreation,” said Michael Cavallaro, Bullhead City’s municipal entomologist.
Jackie Wallin, president and CEO of the Laughlin Chamber of Commerce, has a background in resort management, plus a hard-earned knowledge of insects that business leaders have a vested interest in controlling.
Laughlin tourism suffered during the peak of COVID-19 restrictions, but less than Las Vegas. Wallin credits that resilience to outdoor recreation. But that can be hard to enjoy when sharing the water with swarming insects.
“They get in your nose and your ears and your mouth,” Wallin said. “It’s really unpleasant.”
Bullhead created an in-house entomologist position to address the caddisfly problem that mushroomed about six years ago.
The reduced-flow project follows up on a similar program that Reclamation, Cavallaro and other partners tested over two days in August and September. Dropping water levels joins traps, stocked trout courtesy of Bullhead City to add more predators, and trials of artificial trout habitats strategically located near caddisfly hotspots and pesticide paint on riverside structures.
Cavallaro said last year’s low flows didn’t appear to affect every nook and cranny equally. He’s still crunching the numbers, but thinks taking away real estate will be the best tool available.
Peak caddisfly season is typically in the spring and fall. Egg masses can contain hundreds of viable eggs. Adult caddisflies are dark brown, less than an inch long and with hairy tent-like wings that, when at rest, make them resemble a computer cursor.
They don’t bite or sting, spread human diseases or damage property or crops, or even make noise. They simply overwhelm.
“They annoy people,” said Nathan Michaels, owner of the local River Passage Water Taxi service. “That’s kind of what they do.”
Michaels, whose fleet transits casino guests between Laughlin’s waterfront resorts and across to Bullhead City, offered one of his boats and pilots to researchers from Bullhead City and the Clark County Vector Control department to study caddisflies and drop in-water treatments that control the biting blackflies and mosquitos.
The boat captains aren’t scientists, but they have a good relationship with the people who are and they want to help everybody benefit, Michaels said. They’re also good liaisons with guests who have to grit with them through the “wall of caddisflies” from Riverside to Harrah’s.
Smicridea fasciatella are native to this region of the Colorado, and not without an ecological function, Cavallaro said. They eat algae and particulate matter in the water, making them important for nutrient cycling.
But the cycle has halted after the U.S. Fish and Wildlife Service temporarily stopped raising trout at its Willow Beach hatchery in 2014 because failures of intake valves led to the loss of thousands of fish.
Meanwhile, Cavallaro says, the invasive quagga mussel, a dime-sized bivalve that hitchhikes into waterways on boat bottoms, took hold in the river, filtering the water to aquarium-like clarity. This increased light penetration and allowed algae and moss — in this case, food’s favorite food — to flourish.
And of course, the Colorado River is not in its natural state. Riverbeds are less muddy and silty, more cobbled. Caddisflies deposit their eggs on these rocks and crevices, an artificial fortress for baby caddisflies.
Fewer predators. An algae buffet. Armored nurseries. Essentially, man terraformed this short stretch of river below Davis Dam for caddisflies’ benefit, Cavallaro said. That led to too much of a good thing.
“We have like this Goldilocks zone of the specific habitat that they really prefer and plenty of food for them to eat,” Cavallaro said. “There are a number of predators in the river, fish and predatory insects, that will eat them, but it’s simply a bioenergetics equation that’s gone wrong. There’s just too many of them for them to eat.”
Anyone who has sat on a bench overlooking the rippling river or done the “Bullhead salute” — frenetic swatting around their face to break up the chaotic screen of dive-bombing bugs — knows caddisflies have delicate bodies that turn to mush when smushed. But it’s far more effective to exterminate the insects en masse before they reach their airborne pesky adulthood.
Uncovered by water, where the caddisfly spends most of its life, the eggs and larvae become vulnerable to dehydration and predation.
The Bureau of Reclamation planned to drop its overnight releases from Davis Dam to about 1,800 cubic feet per second — less than a tenth of the dam’s full output — from midnight to about 4 a.m., on May 24 and 27, June 2-3, and June 8-10.
The bureau said the river returns to regular levels after a few hours of higher releases.
Caddisflies favor still air, so when a breeze disrupts the swarming behavior enough to give boat captains like Art Martin a mostly unobstructed windshield, it’s a welcomed change of pace.
Martin, a River Passage Water Taxi pilot, said that with a breeze of a recent Wednesday the bugs were basically trivial, even though he still did a reflexive dance at the helm of his boat to evacuate a few that flew up the legs of his shorts.
“As captains, we don’t like wind,” he said. It makes navigating the water harder. “But trust me, we like wind.”
The insects’ witching hour is at dusk, when the sun drops below the horizon and bats emerge from eaves and the swallows from the trees to hunt. If they’re looking for a caddisfly meal, they’ll find it, because this is when the caddisflies swirl and undulate by the hundreds and thousands.
They also swarm at dawn. When it gets hotter than about 105 degrees, they slow down and take a midday nap, Cavallaro said. On days when it’s warm but not hot, at least by local standards, the insects can be out all day.
At night, they retreat, although like true moths, they can be drawn to artificial light. A handful of caddisflies flitting around a light fixture inside the Riverside casino demonstrates this.
Mostly unbothered as Martin was when steering his taxi from waterfront hotel to hotel — he only banged on his windshield to scare off bugs a couple of times — his passengers noticed what was waiting for them at the docks.
“Look at them over there” one woman said to her companion as the boat eased into the Aquarius dock. Caddisflies crowded a pole like bees on honeycomb.
“That’s so nasty.”
Wallin is sanguine about the future. She thinks the fall test run with low dam flows made a dent in the population.
Visitors are icked-out by the bugs. They complain. But “it’s temporary for them,” she said.
“Those of us who live here know the ongoing effect.”