The extent of cage aquaculture, adherence to best practices and reflections for sustainable aquaculture on African inland waters

Cage aquaculture is expanding on African inland waters and has potential to close the fish supply deficit in the region and provide other social benefits such as employment and income. However, if not appropriately guided and regulated, cage aquaculture could become unsustainable, causing conflicts with other water uses, environmental degradation and economic losses to aquaculture enterprises. To enhance sustainability of cage aquaculture on the African inland waters, we developed an inventory of cage aquaculture installations and used it to investigate the distribution and magnitude of cage aquaculture and adherence to best practices for sustainable aquaculture. Our results show evidence of spatial expansion of cage aquaculture on the African inland waters, of varying magnitude across and within water bodies and partial adherence to best practices. Cage aquaculture was confirmed on 18 water bodies which together share 263 installations with more than 20,000 cages. Lakes Victoria, Kariba, Volta and River Volta host 82.9% of cage aquaculture installations on the African inland waters and are major areas for cage aquaculture. Contrary to best practices, evidence shows cage aquaculture installations entirely or in close proximity to protected areas, in eutrophic and hypertrophic waters, shallow water bodies and sites (≥5 m average depth) and close to the shoreline. Cage aquaculture is qualified as an additional stressor to the African inland waters and because it is expected to continue expanding, adherence to best practices should be promoted for sustainability.