Wild brown bullhead catfish reveal first transmissible cancer documented in fish

Scientists studying brown bullhead catfish in Lake Memphremagog found melanoma in 23%–37% of sampled fish, and whole-genome sequencing revealed that the tumors across fish are strikingly similar and come from a single cancer cell line, indicating a transmissible cancer—the first known case in fish and the first documented in a freshwater species. The route of transmission is not yet known (close contact during spawning is a possibility), and there is no evidence humans are at risk from these fish or the lake water.