Many mink appear to be missing along the Hudson River.

A new study, published this summer in Nature’s Scientific Reports research journal, says the mink population is about 40 percent smaller along the Hudson than it is along the Mohawk River.

The multiyear study was commissioned by the Hudson River Natural Resource Trustees. The study authors concluded that PCB contamination was killing the mink near the Hudson River, saying that was the primary difference between the Hudson River habitat and the Mohawk River habitat.

PCBs are chemicals found in electrical equipment coolants.

The trustees may demand that General Electric pay to restore the mink population.

The trustees have steadily documented the “natural resource injuries” from GE’s releases of PCBs into the river, in preparation for a demand for restoration. They have documented damages to snapping turtles, birds and bullfrogs.

Mink could be assisted with protected habitats along the river or by improving their access to uncontaminated food, water and sediment, the trustees said in a press release.

“Decades of PCB contamination continue to have severe and adverse effects on entire populations of animals, such as mink, in the Hudson River,” said Kathryn Jahn, Department of the Interior’s case manager for the Hudson River Natural Resource Damage Assessment, in a statement. “Habitat and wildlife restoration, or land protection, by General Electric to help address this problem could begin at any time.”

Trappers said they would not be surprised to learn that PCBs were killing off the mink. One wife of a local fur buyer noted that she had several fur coats — but not a mink coat, because mink is so rare.

But former Conservation officer and Argyle Supervisor Bob Henke cautioned about assuming the mink population was affected only by the PCBs.

“The big problem is winter feed. They eat a whole lot of muskrats out of their dens. If the muskrats are down, the mink are down,” he said. “It’s very hard to tell.”

Still, he acknowledged that it is startling to see such differences in population between the Hudson and Mohawk rivers.

While mink do not eat many fish — which are so contaminated by PCBs that humans are advised not to eat them — he noted that mink do eat other animals that are known to be contaminated.

“There was a study that showed the birds are picking up PCBs and the mink do eat a lot of ground-nesting birds in the spring. So that may be a vector,” Henke said. “That might be conceivable.”

Researchers for the study spent two years searching for mink feces to determine the size of the mink population along both rivers. They used dogs to sniff out the feces, and then DNA analysis to identify each mink. They found 108 mink in the Hudson River habitat, compared to 208 mink in the Mohawk River habitat.

A previous study, in 2013, tested how mink react to PCBs by feeding PCB-contaminated food to captive mink. Baby mink died more often and adult mink developed lesions in their jaw bones that eventually caused their teeth to fall out.

Mark Behan of Behan Communications, who was hired by GE to respond to press inquiries about the PCB issue, disputed the conclusions in the study. He noted the PCB cleanup finished just three years ago and that PCB levels are falling.

“The Hudson River is an environmental success story,” Behan said. “A limited study of comparative mink scat findings does nothing to diminish the success of the historic Hudson River cleanup that reduced PCB levels in sediment by 92 percent or the ongoing environmental recovery of the river as a whole. Indeed, all signs point to continued progress.”