Inside the carp: Minnesota’s new scanner joins the search for a sound barrier

The effort to keep invasive carp from spreading through the Mississippi River basin has long included an unusual kind of barrier: sound. University of Minnesota researchers are now approaching that problem from inside the fish. A newly installed CT scanner at the Bell Museum in St. Paul lets them examine intact specimens in three dimensions—and investigate whether carp anatomy could help identify sounds that discourage invasive fish without blocking native species.⁠²⁶⁠¹

That is a new research capability, not a demonstrated new defense for Minnesota waterways. The scanner can reveal internal structures without dissection. Whether those structures point to a sound carp will avoid, and whether that response lasts, remains to be established.

The instrument is a Nikon VOXLS 20 C-225 micro-CT scanner. The university announced its acquisition on August 3, 2026, and described it as installed in an October 14 article. CBS Minnesota’s November 4 report adds a concrete explanation of the carp question researchers hope to pursue with it.⁠¹³⁠¹¹⁠¹

As a specimen rotates, the machine collects a succession of X-ray views. A computer reconstructs them into a three-dimensional object, allowing researchers to examine the interior while leaving the original specimen in one piece for future study. “Then, the computer does a whole bunch of complex math to turn that into a 3D object,” Kassandra Ford told CBS Minnesota.⁠¹

Ford is the Bell Museum’s curator of fishes and mollusks and a University of Minnesota assistant professor in fisheries, wildlife and conservation biology. She wants to investigate how invasive carp skulls evolved and whether their anatomy offers clues to differences in hearing. The practical ambition is to find sounds invasive carp detect that native fish do not.⁠¹³⁠¹

There are several steps between a detailed image and that outcome. An anatomical difference must first be connected to hearing. Detecting a sound must then translate into avoiding it. And avoidance has to remain useful after repeated exposure, without discouraging native fish from moving through the same water.

The reported CT work has not yet demonstrated that chain. Ford’s account identifies no successful frequency, measured hearing range, native-fish comparison or completed sound trial arising from the scans. It also does not identify which carp species her scanning project targets. The distinction is important: Minnesota classifies silver, bighead, grass and black carp as invasive, while the hearing and deterrence research discussed here specifically concerns silver and bighead carp. Results for those two cannot simply stand in for all four.⁠¹⁠²³⁠²²⁠²⁶

Separate acoustic experiments show how researchers are approaching the behavioral part of the problem. A 2025 study in Transactions of the American Fisheries Society placed transmitter-equipped silver carp in earthen ponds with underwater monitoring arrays. Researchers exposed the fish to 30-minute playbacks of three sounds: chirp saw, chirp square and a 100-horsepower boat motor. The available abstract excerpt describes that setup, but does not establish how effectively any of the sounds deterred the fish. Those experiments were not results of Ford’s imaging work.⁠²⁵

Another 2025 paper, in PLoS ONE, describes broad-frequency acoustic deterrents as promising and under assessment in Mississippi River navigation-lock chambers. Such nonphysical barriers seek to reduce carp passage while allowing vessels through. But the paper’s abstract also identifies the central limitation: no single deterrent is completely effective, and fish may become accustomed to repeated sound.⁠²⁶

A 2026 review by Allen F. Mensinger reports variable success with acoustic deterrents and a relatively thin foundation of controlled or long-term studies. Some reports also fail to specify the sound sufficiently—a problem when the sound itself is the intervention being tested. A response during one exposure is not enough to establish lasting protection for a waterway.⁠²⁷

Sound nevertheless has practical attractions. It can travel considerable distances, is relatively independent of light and weather, and need not interfere with navigation. The review also describes acoustic deterrents as relatively inexpensive to implement. Those are reasons to keep investigating, not an effectiveness guarantee or a price estimate for anything that might emerge from the Bell Museum’s scanner.⁠²⁷

The scanner’s value extends beyond the possibility of a fish deterrent. Ford singled out a bat skull as especially striking in three dimensions and described opportunities to examine evolutionary anatomy across preserved animals. The equipment can support student research, with carp among dozens of possible applications. Her reference to animals with histories stretching back hundreds of millions of years concerns their evolutionary lineages, not the age of the museum specimens.⁠¹

The funding also covers a broader project. Ford’s original proposal for “Visualizing Minnesota’s Natural Resources with CT-Scanning” requested $1,062,000. The approved work plan lists a $955,000 project budget; it was submitted June 5, 2025, and approved June 24. Neither figure establishes the scanner’s stand-alone purchase price. Treating the whole project budget as the equipment’s price would give readers a precision the documents do not support.⁠¹²⁠²

The largest number associated with the scanner needs similar care. Researchers describe a prospective scope of up to three million specimens, including insects, birds, reptiles and mammals. The university’s October account similarly refers to about three million specimens. That is not a completed-scan total, a demonstrated annual processing rate or a verified completion deadline.⁠¹⁠¹¹

There is an unresolved counting issue, too. The Bell Museum’s collections page lists more than 1.2 million scientific specimens. The available accounts do not reconcile that inventory with the roughly three-million-specimen scanning scope or explain whether they use different definitions or include different holdings. The figures should not be substituted for one another.⁠¹⁴⁠¹¹

The ecological prize is not simply making carp move away from a noise. It is discouraging invasive fish while preserving passage for native species. The scanner gives researchers a more detailed place to begin that investigation. The test of its contribution will come when the anatomy can be connected to behavior that works beyond the first encounter.