Curbing the Chub: USU Aquatic Ecologist Works to Restore Balance

In a study funded by the Utah Division of Wildlife Resources, Utah State University graduate student Lisa Winters is investigating ways to keep the prolific Utah Chub, a freshwater member of the minnow family, from crowding out native trout in central Utah’s Scofield Reservoir. Here, Winter shares insights from her research.

How do you stop an exploding population of an unwanted fish, quickly and effectively, without ruining the native trout fishery so popular with Utah anglers?

This is the basis of my graduate research work as a member of USU’s Fish Ecology Lab. For the past two years, I’ve made periodic trips to Scofield Reservoir, a 2,815-acre man-made lake on the Price River in the heart of the Manti-La Sal National Forest. With guidance from professor Phaedra Budy, my advisor in the Department of Watershed Sciences, I’ve spent nearly every daylight hour catching fish, measuring their length and weight and extracting valuable body parts to determine how fish in the reservoir are performing.

I work with Bear Lake cutthroat trout, rainbow trout and tiger trout, along with vast numbers of Utah Chub. The chub, a carp-like fish not native to the Colorado River drainage where Scofield is located, is where the problem lies. The introduced fish reproduces often and exhibits exceptionally fast growth.

Since the chub’s 2005 appearance in the reservoir, anglers have observed a substantial decrease in the rainbow trout fishery as well as an exponential increase in the chub population. Needless to say, the fishermen are not thrilled.

Tasked with managing Utah’s fishing opportunities, the Utah Division of Wildlife Resources has worked to mitigate the chub problem with the use of ‘biological control agents.’ This process involves use of top predators that consume vast amounts of unwelcome prey. In Scofield Reservoir, the UDWR has stocked Bear Lake cutthroat trout, a popular native fish of the state, along with tiger trout, a hybrid species known for its fast growth and aggressive nature, as potential biological control agents to curb the chub.

After seven years of efforts, the UDWR is beginning to see an impact. Working with the agency, I’m trying to determine what and how much the biological control agents are consuming. With this knowledge, I can simulate the Utah chub consumption potential for each species. My findings show each individual adult cutthroat or tiger trout may consume 20 chub in a single year. Multiply that by 100,000 of each species in the reservoir, and you can see a lot of Utah chub are being eaten.

Unfortunately, rainbow trout, which once made Scofield a great fishery, have not fared as well. Rainbow trout are not known to be fish-eaters and, in fact, I’ve found they consume many of the same aquatic organisms as Utah chub. Thus, the iconic rainbows are disappearing from the lake — they simply can’t compete with the voracious chub.

Our work has broad implications for the many reservoir systems throughout the West. Like Scofield, many of these waters have unique and artificial assemblages of fish which make them vulnerable to unwanted invaders capable of altering the species composition. My hope is that, by informing the management decision-making process, I will help find the delicate balance between predators and prey and, for Scofield Reservoir, return it to the thriving blue-ribbon fishery it once was.

An aspiring science writer, Winters shares research activities of members of the USU student subunit of the American Fisheries Society in the chapter’s blog. Her research is featured in Utah State Today as part of Natural Resources Week at USU March 25-29.

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Writer/Contact: Lisa Winters, lisa.winters@aggiemail.usu.edu