WWW.WAS.ORG • WORLD AQUACULTURE • DECEMBER 2014 61 Mitigating Eutrophication in Lakes and Reservoirs The success of cage culture in Nigerian lakes and reservoirs depends on good water quality, which requires the reduction, control and management of cultural eutrophication. Mitigating measures for cultural eutrophication before the use of the lakes and reservoirs for cage culture should involve the following strategies. An initial environmental examination provides a baseline assessment of the sources, quantities and concentrations of nutrients in the lakes and reservoirs to be used for cage fish culture. This will show the causes and potential severity of the eutrophication expected and possible mitigation measures that could be implemented before commencing cage culture. An environmental risk assessment from the perspectives of fish stocks in the cage should be carried out in association with the initial environmental examination. Lakes and reservoirs with large watersheds should not be used for cage culture because of the erosive tendency and high level of human activities on such watersheds. An environmental impact assessment should be carried after the beginning of cage culture project. These assessments will provide information and data on eutrophication, ecological interactions and the impacts of watershed uses. This could then be used to guide management and operation of the cage culture project. There should also be regular monitoring of anthropogenic activities in the watershed that can cause cultural eutrophication. Geographic Information Systems (GIS) allows effective environmental management planning. The usefulness of this methodology for site selection in cage fish culture has been explored and is now becoming widely established (Perez et al. 2003). Best management practices (BMPs) in the watersheds of lakes and reservoirs should be adopted (Mustapha 2009, 2010a, 2010b). These include nutrient control, biomanipulation, regulations, public awareness, environmental education and changes in social and cultural perspectives of lakes and reservoirs. These will go a long way to mitigate cultural eutrophication. Conclusion The prospects of cage fish culture in providing cheap fish protein, sustaining livelihoods, alleviating poverty and ensuring food security largely depends on water quality in the lakes and reservoirs where cage culture is practiced. Good water quality depends on effective curbing, control and management of the threat of cultural eutrophication. An integrated and synergistic approach among various sciences, culture, society, legislation, governmental and non-governmental entities is necessary. Their involvement and participation in management and control of eutrophication will help to ensure that lakes and reservoirs have water quality that will sustain cage fish culture and thereby making the advantages of cage culture feasible and realizable. Notes Moshood Mustapha, Dept. of Zoology, University of Ilorin, Ilorin, Nigeria moonstapha@yahoo.com +2348035797590 References Allan, J.D., R. Abell, Z. Hogan, C. Revenga, B.W. Taylor, R.L. Welcomme and K. Winemiller. 2005. Overfishing of inland waters. Bioscience 55:1041-1051. Beveridge, M. 2004. Cage Aquaculture, Third Edition. Blackwell Publishing Ltd. Oxford, UK. Carpenter, S.R., N.F. Caranco, D.L. Correll, R.W. Howarth, A.N. Sharpley, and V.H. Smith. 1998. Non point pollution of surface waters with Phosphorous and Nitrogen. Ecological Applications 8:559-568. Das, A.K., K.K. Vass, N.P. Shrivastava and P.K. Katiha. 2009. Cage Culture in Reservoirs in India. (A Handbook) WorldFish Center Technical Manual No. 1948. 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