Nature, Published online: 22 July 2026; doi:10.1038/d41586-026-02236-7 Transmissible tumours have been found in only a few types of animal, but there might be many more out there.
A team of Vermont researchers has discovered that mysterious black skin lesions afflicting catfish in Lake Memphremagog and other New England and Canadian lakes are caused by a transmissible cancer—the first identified in a freshwater fish species.
For more than a decade, there’s been something fishy going on in a lake that straddles Vermont and the province of Quebec. It involves cancer, a kind of catfish, and — possibly — clues about how tumors metastasize. (Image credit: Joshua Brown)
Researchers identified a form of transmissible cancer in a freshwater fish species, in which the cancer cells behave more like parasites than conventional tumors, moving from fish to fish.
For more than a decade, anglers on a lake straddling the border of Vermont and Quebec have noticed that some brown bullhead catfish are covered in black growths.
