Climate-fueled wildfires worsen danger for struggling fish

The state's largest wildfire on record had roared perilously close to their previous home, torching trees and undergrowth on nearby slopes. Summer monsoon season was approaching, and heavy rains could sweep ashy muck into the creek, clogging fish gills and smothering gravel bottoms where they feed and spawn.

State and federal crews rushed to the rescue, using electrofishing gear to stun and net as many cutthroat as possible. They were trucked south to Las Cruces and kept in tanks at New Mexico State University until Middle Ponil Creek was readied to host them.

Today, wildlife agencies in the southwestern U.S. consider missions like this essential as climate change brings more frequent and hotter wildfires, fueled by prolonged drought and tree-killing bug infestations. Particularly vulnerable are Rio Grande cutthroat trout and gila trout — rare species found mostly in small, high-elevation streams.

"With every fire, more of their populations are being affected," said Jill Wick, native fish program manager for the New Mexico Department of Game and Fish. "Their habitat is often gone, washed out of the creek. There's no place they can hide and cool off. Their food is decimated as well."

The danger is rising elsewhere. Tens of thousands of salmon, trout and other fish perished in August when a flash flood swept through a burn area in Northern California, sending a sludge plume into the Klamath River.

Trout numbers fell up to 80% in sections of Colorado's Cache la Poudre River after floods and mudslides in summer 2021, a survey found. The biggest wildfire in state history had burned 326 square miles (844 square kilometers) in that area the previous year.

LOCATION MATTERS

Fire isn't always bad for fish. Many species evolved to benefit from the "patchiness and diversity" wildfire brings to landscapes and waterways, said Dan Isaak, a U.S. Forest Service fisheries scientist in Idaho.

The one-two punch of fire and torrential rains is less common in northern regions. Ash tends to stay put through winter snows and seep into the ground or trickle into streams during spring thaws. It delivers nutrients for algae eaten by insects that become fish food. Burned trees topple into streams, creating pools and riffles for feeding and spawning.

But farther south, ever-larger fires incinerate so much foliage holding soil in place that heavy debris flows cause oversized algae blooms that can suffocate fish.

Their health also depends on surrounding features such as slope steepness, plant life and soil types, said Christopher Clare, a habitat protection biologist with the Oregon Department of Fish and Wildlife. And, Clare said, climate change is heating streams, a problem worsened when fire robs banks of shade trees.

Rebecca Flitcroft, a U.S. Forest Service fish biologist in Corvallis, Oregon, has modeled danger that fire poses to spring Chinook salmon and bull trout in Washington's Wenatchee River system feeding the Columbia River.

While both species are imperiled, results suggest the trout are worse off because they occupy isolated, cold headwaters. Fire intensity there is higher than in lower portions of river systems preferred by Chinook for easier access to the Pacific, Flitcroft said.

Man-made changes to waterways and landscapes make it harder for fish to survive during and after fires, she said. Water diversions have shrunk habitat. Low levels caused by drought, plus culverts, roads and dams, prevent fish from fleeing to cooler spots.

"We're at a critical place right now with very intense fires, compounded with highly disturbed systems that don't allow for connectivity and movement," Flitcroft said.

CUTTHROATS IN TROUBLE

The Rio Grande cutthroat, New Mexico's state fish, has long been going downhill. Drought and dams have disrupted its habitat. Nonnative brown and brook trout, stocked for sport angling, compete for food. Introduced rainbow trout interbreed with the cutthroat, diluting its genetics.

Named after the reddish slashes beneath its lower jaw, the colorful cutthroat occupies about 12% of its historical range in New Mexico and Colorado, according to a 2019 study that predicted continued decline.

New Mexico had 92 Rio Grande cutthroat populations at the beginning of this year.

The U.S. Fish and Wildlife Service in 2014 rejected a petition to place the cutthroat on the federal endangered list but was overruled by a federal judge and is reconsidering. The nonprofit Center for Biological Diversity had sued for the designation, saying the trout was "barely hanging on."

But a listing could bring land-use restrictions that many would find unpopular, said Toner Mitchell, New Mexico water and habitat coordinator for Trout Unlimited.

"There's a risk of demonizing or villainizing the Rio Grande cutthroat," Mitchell said. "That could result in anything from vandalism to outright efforts to exterminate the fish, when by and large, longtime residents prize them."

Teams have rescued cutthroat and gila trout from New Mexico streams more than two dozen times since the late 1980s.

"Before these mega-fires, it might be one or two populations in trouble at one time," Wick said. "Now, it's two or three times as many."

Nine cutthroat streams were within this summer's Calf Canyon-Hermits Creek blaze, which began as two fires set to clear undergrowth but blew out of control, consuming more than 530 square miles (1,373 square kilometers).

Ash wiped out at least one stream's cutthroats. Trout were salvaged from three others. Among them was Rito Morphy, a twisting, tree-lined creek in the Sangre de Cristo mountain range.

Not all of 190 fish from there survived the stress of two road trips and a months-long stay in university tanks. But the effort kept most alive until a new habitat could be prepared in Middle Ponil Creek, about 58 miles from Rito Morphy.

That required poisoning rainbow trout in the stream section where the fish would be placed. "We want to make sure the cutthroat stay genetically pure," said U.S. Forest Service biologist Alyssa Radcliff.

It's ecologically important to preserve a rare strain of fish, Radcliff said. Another goal is making more available for anglers. "A lot of people were taken by their grandpas and their grandmoms to these streams to catch these fish," she said.

FREE AT LAST

On a recent sunny, windswept afternoon, a pickup truck stopped alongside a dirt road in Carson National Forest. Workers scooped cutthroats four to eight inches (10 to 20 centimeters) long from a large cooler into several five-gallon (19-liter) buckets, strapped them onto backpacks and lugged them through a meadow to the brush-lined, boulder-strewn creek.

When the buckets were tilted into the stream, the liberated fish darted about in the clear water and swished tails in the sandy bottom. Their new digs extended from the creek's headwaters to a wire-and-rock barrier 8 miles (12.8 kilometers) downstream to keep out rainbow trout.

It was a quick ending for a mission that lasted all summer, said Bakevich, the state's native fish supervisor.

"After doing all the hard work and coming here," he said, "this is the best part."

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Flesher reported from Traverse City, Michigan.

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Follow John Flesher on Twitter: @JohnFlesher.

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