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The amazing ecosystem engineer of Southwest Virginia: The bluehead chub

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(© josephsjacobs – stock.adobe.com)

An engineering marvel is being constructed right now in a creek in Southwest Virginia.

It begins when a male bluehead chub minnow picks up a small piece of gravel in his mouth and drops it on the silted creek bottom. Then he does it again and again — ultimately, 20,000 to 100,000 times — carefully moving each individual pebble to its new location up to 10 feet away.

At some point, one or two other males join him, coordinating their efforts and becoming less territorial within the shared boundaries of their new nest. As a small mountain of stones slowly emerges, other minnow species arrive, laying their eggs along with those of the bluehead chub in a vivid flurry of color over the stone mound nest.

The remarkable nest-building abilities of the bluehead chub have been largely overlooked by those studying how animals protect their young in order to gain a survival advantage amidst a herd, flock, or, in this case, school of fish. Through a four-year, $1 million grant from the National Science Foundation, Virginia Tech researchers hope to decipher the nest-building secrets of the bluehead chub to learn more about conserving its threatened companions.

Although the bluehead chub is a common type of minnow in that it flourishes in the streams of Southwest Virginia, its nesting behaviors make it unique. “It’s one of about 10 species, out of 34,000 species of fish that we know of globally, that is actually able to carry pebbles in its mouth to build a nest — a mound nest — so this is a very rare trait,” said Emmanuel Frimpong, the project’s principal investigator and professor of fish conservation in the College of Natural Resources and Environment.

Once a chub nest is constructed, up to 40 species of minnows, some of which are endangered, may use it as a place to lay eggs. The presence of so many species serves to protect the fish from predators while they are spawning, and the mounded nests themselves function as a haven for developing eggs and larvae.

Frimpong, a faculty member in the Department of Fish and Wildlife Conservation and an affiliate of the Global Change Center housed in Virginia Tech’s Fralin Life Sciences Institute, has been studying bluehead chubs for 14 years. As he began to understand the critical role they play in North American stream ecosystems, he also began to rethink how to approach conservation within these environments.

“Because bluehead chubs are relatively common, we don’t think of them as a species that needs protection,” Frimpong explained. “Yet the protection of other species that are rare and dependent on the chub will depend on understanding the role of the chub in the lives of these rare species and, ultimately, conservation of the chub.”

Seeking to understand more about the role and behaviors of the chubs led Frimpong to ask more complicated questions about what these minnows were doing and why, questions involving factors like water flow and oxygen levels within their nests. Because he realized that “what these chubs do is literally engineering,” the next step for his research became apparent: “Chubs are ecosystem engineers, so to study their nests, you need engineering tools.”

Luckily, one of Frimpong’s colleagues at the Global Change Center, which provided support for a seed project leading to the current project, is Assistant Professor Hosein Foroutan, an expert in environmental and geophysical fluid dynamics in the Charles E. Via, Jr. Department of Civil and Environmental Engineering.

Foroutan constructs physical and mathematical models that can be used to predict fluid flow, which, in this case, is water moving through and around the bluehead chub nests. For this project, he plans to construct three-dimensional dynamic maps that show the flow and velocity of the water as well as what happens to the oxygen concentration as water moves through the stone mound nests.

The models, when combined with observations of fish behavior, should allow Frimpong to determine whether the bluehead chubs — or the other minnows that use the nests — are gaining an advantage by using the best locations in the nests for spawning and laying their eggs.

According to Foroutan, it is the interdisciplinary nature of the research that will allow the researchers to answer these complicated questions at the intersection of biology and engineering, opening new doors and providing results that a researcher cannot attain individually.

“No matter how advanced these models are, if we don’t combine them with the fish behavior, we don’t really know what’s happening in the nests in nature,” Foroutan said. “And no matter how much we look into the fish behavior without knowing really what’s happening in the nest, without developing knowledge of the fluid flow and oxygen concentration, we really don’t know if this behavior is relevant.”

Throughout the spring and summer, Frimpong and his team of student researchers will be making daily checks on and collecting data at nests located in or near Blacksburg in Toms Creek and the north fork of the Roanoke River.

Graduate student Emma Hultin, who collaborated with Frimpong as an undergraduate researcher, will work on the project while also continuing her own master’s research. She’ll collect data on stream microhabitat around the nests, as well as some of the fish and eggs she finds within the nests, hoping to create niche models that describe the environmental conditions required for successful spawning of the chubs and associated minnows.

She credits Frimpong with both introducing her to the bluehead chub and getting her started in research. “I’m a first-generation college student, so having the support and mentorship of Dr. Frimpong as an undergrad was crucial,” she said. “He took a chance on me and welcomed me into this project, providing me the opportunity not only to conduct undergraduate research but to advance to graduate school and get experience running my own project and collaborating with other professors.”

Hultin is also supervising and training undergraduate students working on the project, including Tal Tomlinson, a fish conservation major. As a research technician, Tomlinson will work with Hultin to complete daily stream observations and collect and perform genetic analyses on eggs.

He’ll be using this summer research experience to fulfill his department’s experiential learning requirement by completing his own study on the Blacknose dace, one of the minnow species that utilizes the chub nests. “Before this project, I hadn’t had the opportunity to be part of in-depth laboratory and genetic research,” Tomlinson said. “I am fortunate that this project is providing me that exact opportunity. It also provides me firsthand experience on how to deal with small nongame fish, many of which I hope to have the opportunity to work with in the future” as a graduate student.

Although Frimpong and the student researchers are spending much of their time in the field, they’ll also bring specimens back to the lab, where they can manipulate the conditions they find in the field and study the responses and survival rates of eggs without interfering with the nests.

Foroutan will also turn to the lab — albeit the computer lab — once he and Associate Professor Kyle Strom, a civil and environmental engineering colleague, complete their precision field measurements of nest size, temperature, and water flow. He’ll develop computer models of the nest fluid movement and oxygen concentrations, models that he will then eventually go back to the field to test.

In terms of the impact of this project, Frimpong hopes for conservation insights as well as public engagement. Outreach is a major part of the project and will include the production of a documentary directed by Eugene Maurakis, a research scientist and adjunct professor at the University of Richmond who has studied chubs for 40 years.

Outreach is also why Frimpong intentionally chose some stream ecosystems for the project that are in public areas, such as Blacksburg’s Deerfield and Heritage parks. He hopes that when people see him or the students working, they will stop to ask questions about these amazing engineers and learn about their importance to the streams they live in.

“We are trying to make public education a central theme of this work, and that’s why a big part of our study site is in public areas like parks where we can encounter people and tell them about the treasure that is here that many may not know about.”

Story by David Fleming


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