(Uploaded by Plazi for the IPBES Invasive Alien Species Assessment) The introduction and establishment of arapaima (Arapaima gigas) in southeastern Peru and northwestern Bolivia is an example of a fish species that appears to be increasingly common and widespread in non-native portions of its range, but whose populations are on the decline within its native range. The arapaima is overfished and considered threatened throughout its native range in the Central Amazon. We gathered and examined data on the distribution of fish and wildlife in the Takana II Indigenous Territory in Bolivia, near the arapaima's reported initial invasion zone in Peru. Results confirmed the presence of arapaima in several water bodies where local people have also reported a strong decline in native fish populations. Further south in the Takana I Indigenous Territory, monitoring of fisheries by local communities (2002-2008), including observations on arapaima catches, indicate that until 2008 arapaima had not been reported in the area. However in 2009, there were reports of arapaima in the Undumo stream. Our results demonstrate that since the first presence of arapaima in Bolivia at the beginning of the 1980s, it has steadily expanded its distribution. We propose actions to mitigate this situation by managing and controlling populations of this invasive and endangered species, as well as improving income for indigenous communities.