This case study of a fish market near the border of Namibia and Zambia examines how economic and environmental changes have affected the marketing channels associated with fishery in southern Africa. We monitored the volume and origin of fish entering the market in Katima Mulilo, Namibia, between 2007 and 2012, and conducted semi-structured interviews with fish committee members and market vendors. Prior to 2010, the market for fish had a simple commodity chain, involving local producers and consumers. Since then, a nearby lake has refilled, providing a new source of fish. The market has expanded and diversified, with large volumes of fish now being sent to consumers in urban centres in Zambia and even to the Democratic Republic of Congo. We consider the sustainability of the fishery in relation to expansion and re-alignment of the marketing channel and the degree to which intra-regional trade in fish promotes or hampers food security and sustainable use of the resource.