Human activity-associated establishment of invasive mink population estimated using environmental DNA

Invasive species are one of the most significant factors affecting biodiversity. American mink (Neovison vison) was introduced to Hokkaido, Japan, and is known to compete with other medium-sized mammals and prey on freshwater fish. Therefore, it is important to understand their distribution and the types of environments they prefer. We developed an N. vison-specific environmental DNA (eDNA) detection assay to estimate their distribution. Applying this assay to water samples from 48 rivers in the Shiretoko Peninsula, the World Natural Heritage site in Hokkaido, N. vison-specific DNA was identified in 10 rivers. Including seven rivers from a previous study on N. vision distribution in the peninsula, the environmental characteristics of the 17 rivers with the potential establishment of N. vison populations were investigated using a generalized linear model. The evaluated environmental factors included eDNA concentrations of two salmonid species (Salvelinus curilus and Oncorhynchus masou, potential food resources for N. vison), the presence of salmon hatchery and release programs, land uses around the rivers, and river structures. While the estimated N. vison distribution did not show a clear association with the eDNA concentrations of the two salmonid species, it showed positive and significant associations with the salmon release programs (p = 0.031) and with the proportion of farmland (p = 0.034). These findings imply that human activities have the potential not only to cause the introduction of invasive species but also unintentionally to contribute to the establishment of such species in new environments.