The deepwater cisco (Coregonus johannae) was one of the largest ciscoes in the Great Lakes. Its average length was 30cm (12 inches) and it was about 1.0 kilogram (2.2 pounds) in weight. Occurring only in Lakes Huron and Michigan, and inhabited waters between 50 and 150 metres deep, it was difficult to distinguish from other ciscoes and was possibl...