University of Idaho - I Banner
students walk on University of Idaho campus

Visit U of I

Learn about the many reasons the University of Idaho could be a perfect fit for you. Schedule Your Visit

Parents on campus during orientation

Homecoming Oct. 14 - 21

Join other Vandal families for a week of celebration and Vandal traditions. View Calendar

campus full of students

U of I Retirees Association

UIRA has a membership of nearly 500 from every part of the University. Learn about UIRA

Students participate in the TRX wellness class at the Student Recreation Center

Campus Recreation

Gym memberships and wellness class passes are available for faculty, staff and their spouses. Get Healthy


University Communications and Marketing

Phone: 111-111-6291

Fax: 111-111-5841

Email: [email protected]

Web: Communications and Marketing

U of I Media Contacts

Catfish Research Relies on Inter-Continental Partnerships

Doctoral student able to study Amazon catfish migrations from Idaho thanks to shipments of fish from Brazil

From the landlocked Palouse, researchers are using new technology to uncover details of one of the world’s longest and least understood migrations, which could aid the conservation of giant Amazonian fish.

Doctoral student Jens Hegg’s interest in the Amazon and the catfish began when he visited Brazil a number of years ago. Since he has a limited research budget, instead of returning to Brazil for this project, he is collaborating with Tommaso Giarrizzo, a faculty member at Federal University of Pará in Brazil. Giarrizzo provides Hegg with samples of the South American fish donated by fishermen at the local markets in Brazil.

Hegg studies the three most numerous species of catfish in the Amazon, all showing a much more complicated migration pattern than previously believed. The new information comes from studying the inner ear of the ancient fish.

Studying the Rings

The view under Jens Hegg’s microscope looks like a task from any basic forestry class: count the rings of the tree and determine the age.

By studying a stone-like structure called an otolith, which is taken from the inner ear of the catfish, Hegg is able to document the movement of the fish. Much like the rings of a tree show the tree’s age, the otolith builds in layers, each chemically different based on the environmental differences along the Amazon. The rings of the otolith tell the life story of these colossal fish, which migrate up to 3,400 miles through the diverse Amazon River basin.

The research shows that each ring in the otolith records a change in location within the enormous Amazon basin. To reconstruct those records, the layers are compared to the unique chemical and isotopic signature of each river, indicated by the mix of rocks in each watershed. This technique gives details of the fish’s movements that are much finer than conventional tagging technologies.

The technique of analyzing the layers of the otoliths was developed by Brian Kennedy, associate professor in UI’s College of Natural Resources. Kennedy uses it to track Northwest salmon species.

A Close up image of a microscope slide that is labeled BF5.
Jens Hegg examines small stone-like structures called otoliths, taken from the inner ear of Amazonian catfish, in order to study the fish’s migratory patterns.

Collaboration Key to Success

It was Kennedy’s research, and Hegg’s desire to apply the technique to fish of the Amazon, that led Hegg, a Northwest native, to return to his roots for graduate school after studying and working in the Midwest. Hegg is a doctoral student in UI’s water resources program, studying within the Fish and Wildlife Sciences Department in the College of Natural Resources.

“It has given me the opportunity to find my feet as a scientist,” Hegg said. “The Fish and Wildlife Sciences Department is a community you end up being heavily involved in. That has been good for me.”

That academic family is important as Hegg continues toward his doctorate. He published his third article this summer in PLOS ONE, an online peer-reviewed scientific journal. He also hopes to obtain funding for additional Amazonian research.

“We found the fish have a very complex migratory pattern, which is important for the future conservation of the species,” Hegg said. The native fish is under pressure from fishing and habitat loss from dams.

“The catfish in the Amazon are where salmon were in the 1920s before the impact of human activity,” he said.

In recent years, Brazil installed more than 150 hydroelectric dams, with another 300 in the planning stages. According to Giarrizzo, the effort to stimulate economic growth in Brazil may be coming at the expense of the Amazonian catfish, whose young cannot pass the reservoirs behind dams.

“This research shows that the technology of otolith research does improve the understanding of the movement and ecology of this native fish,” Giarrizzo said. “The collaboration has proven successful and is the first step to creation of an Amazonian research network based on common objectives and standardized procedures.”

Collaborating on an international project has been beneficial for everyone involved.

“The more you interact with other scientists, the better,” Hegg said.

Article by Jodi Walker, University Communications and Marketing


University Communications and Marketing

Phone: 111-111-6291

Fax: 111-111-5841

Email: [email protected]

Web: Communications and Marketing

U of I Media Contacts