Low fish numbers on the Dolores River prompt concern
By Carolyn Dunmire
If you happen to be a trout or a native fish living in the Dolores River, you’re probably feeling pretty lonely. Fish numbers continued to decline despite increased river flows this year, according to Colorado Division of Wildlife fishery biologist Mike Japhet.
Japhet has been studying fish in the Dolores River for 20 years and recent trends in trout and native fish populations are alarming, he told participants in the Dolores River Dialogue at a meeting in November.
The DRD is a diverse group of farmers, boaters, environmentalists, scientists, and government officials dedicated to finding better ways to operate the Dolores River.
Using electro-fishing and other survey techniques, Japhet and other DOW biologists recorded the number and mass of fish in the Dolores River from McPhee Dam to the confluence with the San Miguel River. They found that since 1995, the number of trout between McPhee Dam and Dove Creek has been in decline, despite the DOW’s ongoing effort to stock trout in the river.
At one time, the 11-mile section of river between McPhee Dam and Bradfield Bridge was classified as goldmedal fishing water, Japhet said. The long-term average and goal for trout biomass in this section of water is about 30 pounds per acre. In 2004, DOW measured 10 pounds of trout biomass per acre; this year, they found twice that. However, Japhet added, “For comparison, the trout biomass in the Animas River’s gold-medal waters is 120 pounds per acre.”
In order to reach the goal of 30 pounds per acre, Japhet reported, the DOW stocks the Dolores River with 10,000 rainbow trout and 10,000 native cutthroat trout fingerlings every year. They will continue these efforts with greater emphasis on the Colorado River native cutthroat trout.
The low flows in the river during the past few years have obviously decimated the trout populations, which have a long way to go to reach goldmedal status once again, he said.
In addition, native fish including the flannelmouth sucker, bluehead sucker, and roundtail chub — all small nongame species listed as “sensitive species” on the San Juan Public Lands and t h r o u g h o u t Region 2 of the U.S. Forest Service — are down to “precarious” numbers, according to Japhet. Sensitive species are those that are not yet listed as endangered under the Endangered Species Act but are recognized as in decline.
The roundtail’s historic habitat is around and below the dam on the Dolores, but recently “we haven’t really picked them up anywhere above Bradfield Bridge,” said David Graf, DOW regional water specialist, by phone from Grand Junction. “They’ve been declining.”
Long-term surveys over the past 10 years for the river section between Dove Creek and Big Gypsum launch site recorded these species as “common.” But surveys this year found no flannelmouth suckers, one bluemouth sucker and only a few roundtail chub.
The two suckers have historically been found along the San Juan River and its tributaries. The suckers are still common in the lower San Juan , but not in the tributaries, such as the Mancos and Dolores rivers, according to Japhet.
Graf agreed. “The two suckers are not doing well in the Dolores,” he said. “The general trend is kind of down.”
Furthermore, Japhet said, surveyors noticed only small-sized fish, indicating an unstable population without any large fish.
Finally, Japhet said he had observed green sunfish, a predator of roundtail chub, for the first time in the river. All these observations raise grave concerns about the future of native fish in the Dolores River.
It’s possible one or more of the species may be listed as federally threatened or endangered, which would prompt major regulatory changes.
Graf said the Colorado River native cutthroat trout was recently proposed for listing but the U.S. Fish and Wildlife Service decided that measure wasn’t warranted yet, partly because of aggressive conservation efforts being undertaken. A tri-state agreement among Colorado, Wyoming and Utah signed in 1999 outlines strategies to recover the native cutthroat.
However, there’s concern that the roundtail chub may also be proposed for listing. “The roundtail has got the attention of people, but it has not been formally petitioned,” Graf said.
Colorado has entered into a six-state conservation agreement to try to recover the chub and the two suckers.
The historic drought certainly contributed to bringing the native fish to an all-time low, Japhet said.
He also speculated that the crash in fish populations on the Dolores may be related to river operations and low release levels last March.
“These low flows increase water temperatures and signal to the fish to get ready to spawn, kind of like fruit trees blossoming in the spring,” he explained. “Then, in April we starting spilling a whole load of cold water, messing up the fishes’ spawning, just like a late freeze ruining the blossom set.”
One possible solution, Japhet said, would be to better mimic natural river flows. He said one-quarter of all natural river flow occurs in March. His proposal would increase release levels in March to 100-200 cubic feet per second to keep the water temperatures down and delay spawning.
At the November DRD meeting, Kent Ford, a boater from Durango, voiced support for the proposal, saying he believes boaters “would be willing to give up some of the spill to keep fish alive in the river.”