White River fish facts

RBC I “By far the most frequently captured species is the mountain whitefish,” said Tory Eyre, aquatic biologist for Colorado Parks and Wildlife during his presentation to the White River Alliance last week. Titled “State of the Fish: What’s happening with fish in a challenged White River,” the presentation explored fish species data in the river from 2000 to present.

“What you’re seeing is relative abundance of each species according to the total catch,” said Eyre, referring to graphs which showed the type of fish anglers might be most likely to catch in two distinct “reaches” of the White River. The data is based on 4 fish collection sites where biologists use electro-shock fishing techniques to catch, measure, categorize and release fish back into the river.

The first or “upper” reach of the river includes the Trappers Lake headwaters all the way to Rio Blanco Reservoir. According to data collected by CPW, the top five most prevalent species in the upper reach are:

• Mountain Whitefish

• Flannelmouth Sucker

• Mottled Sculpin

• Rainbow Trout

• Brown Trout

Lower reach data (from Rio Blanco Reservoir to the Utah state line) reveals a different picture “There’s definitely a transition to more of a warm water fishery as you move downstream” said Eyre, noting that within the lower reach, smallmouth bass is the dominant species, particularly below Kenney reservoir. The top five fish for the lower reach are:

• Smallmouth bass

• Green Sunfish

• Flannelmouth Sucker

• Bluehead Sucker

• Fathead Sucker

Eyre noted that data for the lower reach was biased toward the lower stretch below Kenney Reservoir, and also likely inflated the number of smallmouth bass due to the way the study was conducted. A similar bias exists for the upper reach when it comes to Mountain Whitefish, as fish sampling collection methods skewed towards the species more than others.

That said, Eyre still described the smallmouth bass as “a species of concern” for other endangered fish downstream, explaining why the state does not put a catch limit on smallmouth bass, like it does with other species. 

Up until recently, anglers could also bag as many Mountain Whitefish as they could catch, though Eyre noted new regulations imposed a bag limit of 4, and possession limit of 8 fish, which he said also applies to trout. 

The limit is in place despite relatively healthy populations of whitefish in the river, since the species has been declining in other parts of the state. Eyre described the White River as a “stronghold for mountain whitefish” due to a population that might actually be increasing, according to data from one measurement site. 

From another perspective, mountain white fish are particularly susceptible to changing river conditions as a result of ongoing drought and related issues like runoff seasons that are earlier and faster, low streamflows and warmer overall temperatures.

Of the species categorized in CPW’s data, the whitefish are the “least tolerant” to warm water temps, which Eyre said was “a concern looking forward” for the upper reach’s most prevalent fish species based on projected trends for snowpack/streamflow and temperature. Presented data also specified water temperatures at which different species are adversely affected.