First report of aquaculture-mediated introduction of the Nile tilapia, Oreochromis niloticus (Linnaeus, 1758) into Lake Bosomtwe, Ghana

The introduction of a non-native fish species into an aquatic ecosystem presents significant ecological risks if the species is able to successfully integrate into the ecosystem. Lake Bosomtwe in Ghana is an impact crater lake which contains an endemic and a near-endemic cichlid species. Following the establishment of an intensive Nile tilapia (Oreochromis niloticus) cage aquaculture facility on the Lake in 2012 and it closure in 2015, there have been several unconfirmed reports of the capture of O. niloticus from Lake Bosomtwe by local fishermen. On 6th February 2020, the first documented observations of O. niloticus in the natural environment of Lake Bosomtwe were made using seine net catches. Nine more seining activities were carried out between 6th February and 17th April, 2020, and the presence of the O. niloticus was confirmed during all sampling events. Oreochromis niloticus constituted between 2 and 10% of the captured cichlid species composition. The introduction of the species warrants larger-scale comprehensive studies on the possible detrimental interactions with native species, and on changes to ecosystem function.