Editor’s note: This article has been updated to remove inaccurate information about fishing closures in Grand County.

Fish get stressed, too. 

It’s why Colorado Parks and Wildlife closely monitors popular angling spots throughout the year for warming water temperatures, declining stream flows, high sediment loads and other aggravating factors. Any one of these could trigger voluntary or mandatory fishing closures to help species persevere. 

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“It is stressful for a fish to be captured and handled,” said Kendall Bakich, an aquatic biologist for Parks and Wildlife who oversees the Roaring Fork, Coloraod and Eagle river basins. “So adding that on top of these environmental stressors can be a big problem, and we do see less mortality when angling pressure goes down.” 

Rivers in Grand County remain open to fishing at this time.

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What can trigger an emergency fishing closure? 

Per Parks and Wildlife’s fishing regulations, emergency closures can be triggered by a few factors and thresholds. 

Heat, drought, and low water levels are contributing to elevated water temperatures in Colorado’s rivers, depleting oxygen levels and leaving fish vulnerable.

The first is temperature. Once river temperatures rise above 71 degrees Fahrenheit, the agency will issue a closure. When temperatures rise, oxygen levels in the water drop. As a result, fish can stop feeding, become more susceptible to diseases, and ultimately, die.   

Warm temperature and low water levels can also lead to algae blooms in rivers and reservoirs which cause oxygen levels to drop when algae die and decompose.

“Get out early to avoid the higher water temperatures commonly seen in the afternoon and evening,” Martin said. “Anglers are also encouraged to seek out high-elevation lakes and streams, where water temperatures are more suitable and fishing doesn’t potentially add additional stress.”

Martin also urged anglers to add a hand-held thermometer to their fishing kits so they can test the waters they intend to fish.

“Anglers can monitor water temperatures on their own and stop fishing when water temperatures start to approach 70 degrees,” she said.

Second is stream flows, with a closure triggered by flows dropping below 50% of the daily average. When this occurs, fish can become concentrated in small areas, increasing competition for food and making them more susceptible to angling pressure and disease, Bakich said.

For trout specifically, because they “really like to defend and hold bigger portions of the river territories, when they get compacted, they get stressed because they’re you know aggravated by each other and that can increase the opportunity for diseases to develop and transmit,” she added. 

Already this year, Parks and Wildlife rolled out a full-day fishing closure on a segment of the Yampa River below Stagecoach Reservoir due to decreased water flows. While the area has seen these types of closures before, this one was “quite early” as the inflows at Stagecoach were about one-third of what the district typically sees, according to Holly Kirkpatrick, public information officer for the Upper Yampa Water Conservancy District.

Environmental events — such as chemical spills or mudslides, wildfires and other events leading to increased sediment flows — can also prompt closures. 

“​​Turbid waters, waters that are really thick and muddy, actually can amplify hot temperatures at times, too,” Bakich said. 

Following such events, closures can help fish populations recover and for remedies to be implemented. Parks and Wildlife can also roll out emergency closures when dissolved oxygen levels drop, as well as when fish show physical signs of stress, disease or high rates of mortality. 

When Parks and Wildlife uses voluntary and mandatory closures 

For a few reasons, the state wildlife agency tries to keep these closures voluntary versus rolling out mandatory changes. 

“Anglers are pretty in tune with what’s going on in a fishery, and they’re not desiring to fish when the fish are stressed anyway, so it’s not hard to get anglers to stop,” Bakich said. 

Plus, to implement a mandatory closure, the biologists have more hoops to jump through. This includes compiling data, writing a recommendation and getting the regulation approved by the Parks and Wildlife Commission. 

“In the last few years in our area, when we’ve had to do them, the conditions develop pretty quickly, and then we don’t want to wait too long,” Bakich said, adding that the longer the closures take to be put in place, the longer fisheries feel the added stress from anglers.  

“We try to maximize (anglers’) ability to use and enjoy the resource by doing these voluntary closures because they’re much more adaptive than a mandatory process, and once a mandatory process is in place, it could reduce opportunities for longer periods of time,” she added. 

What to expect this year for angling closures 

It can be difficult to predict when and where fishing closures will take place this year; however, they have become more commonplace. In her region, Bakich said there’s been a closure somewhere almost every year for the last decade or so.

Mountain whitefish have been the most sensitive to some of the trends toward lower flows and warming temperatures. The salmonid species is native to the Yampa and White rivers in Colorado and was introduced into the Roaring Fork River in the 1900s.

“We used to have a very abundant whitefish fishery,” Bakich said. “And we’ve seen a virtual collapse of the fishery in the Roaring Fork itself. We still have a pretty healthy population in the Crystal River,  but they are more sensitive to temperature and stressors than trout are.”

In September, Parks and Wildlife implemented a mandatory closure from Oct. 1 through Nov. 15 for the mountain whitefish in their breeding grounds in a Yampa River tributary after voluntary closures were ineffective in mitigating impacts to the species.

So far, Bakich said closures are likely but still largely unknown. 

“We’re certainly concerned because we know flows are already pretty low this year, and we know we have low snowpack,” Bakich said.

According to the latest streamflow report from the U.S. Department of Agriculture, early snowmelt and limited snowpack are resulting in streamflows that are 50% of normal in southern and western Colorado. 

However, while this year’s dry and hot spring could have negative consequences, a good monsoon season could help turn the tide. 

“This year is all going to be dependent on what it looks like with those monsoonal patterns if they develop and can help us get through summers,” Bakich said. “They provide a lot of cold water coming down as rain but they also can create problems like sediment events. So it depends on where the rainwater falls, how much sediment comes down, and how long it’s retained in the river.”

In previous low-flow years, Bakich said she’s been surprised by how rain or reservoir storage has helped the agency curtail expected closures. 

In some watersheds, upstream reservoirs can be used as a tool to help cool water temperatures. Bakich likened it to opening a cold water faucet. 

With a lot still unknown, Bakich recommended anglers continue to observe and report any unusual conditions or behavior as they fish.

“If the fish seem stressed in an area, it is OK to move somewhere else,” Bakich said. 

The Eagle River Coalition and with Lotic Hydrology recently launched an online tool for users to track river flows and temperature within the Eagle River Basin and the Colorado River near Glenwood. It is available at EagleRiverCO.org/RiverReport. 

The U.S. Geological Survey National Water Information System provides state-level data on water conditions, including temperatures, water depth and more.