From the Wikipedia page 
Ukerewe District is one of the seven districts of the Mwanza Region of Tanzania. It is located on Ukerewe Island, Ukara Island and other neighbouring islands within Lake Victoria. The largest settlement and the district's administrative capital is Nansio.
As of 2002, Ukerewe District was administratively divided into twenty-five wards: Bukanda, Bukiko, Bukindo, Bukongo, Bukungu, Bwiro, Bwisya, Igalla, Ilangala, Irugwa, Kagera, Kagunguli, Kakerege, Kakuru Mukituntu, Muriti, Murutunguru, Nakatunguru, Namagondo, Namilembe, Nansio, Nduruma, Ngoma, Nkilizya, and Nyamanga.