Some possible factors leading to decline in fish species in Lake Victoria
Keywords:
exotic introductions, ecological changes, hybridisation, haplochrominesAbstract
The decline in fish species in Lake Victoria is one of the largest documented losses of biodiversity in an ecosystem. The reduction in species in the lake was attributed to overexploitation through increased fishing capacity, use of illegal fishing gears and poor enforcement of regulations. Introduction of the predatory Nile perch is blamed for the decline of the native species, especially the haplochromine cichlids. The native tilapiines, Oreochromis esculentus and Oreochromis variabilis, declined due to hybridisation and competition with the introduced Oreochromis niloticus. Diversity loss in haplochromine cichlids has also been attributed to hybridisation caused by increased water turbidity, which reduces visibility in recognising conspecifics during breeding. Degradation of the environment through poor farming patterns and waste disposal has led to increased nutrients into the lake, in turn leading to changes in water quality, increased algal blooms and subsequent anoxia which led to frequent fish kills in the 1990s. However, recent resurgence of haplochromines thought to be extinct, disputes the fact that extinction of several species occurred. Though not denying that a drastic reduction in the number of native species occurred, the much hyped extinction could be a result of a lack of adequate information on taxonomy and ecology of the haplochromines as well.
References
Abila, R. 2000. The development of the Lake Victoria fishery: A boom or bane for food security?, Nairobi, , Kenya: IUCN. No. 8
Balirwa, J. S. 1992. The evolution of the fishery of Oreochromis niloticus (Pisces: Cichlidae) in Lake Victoria. Hydrobiologia, 232: 85–89.
Cowx, I. G., Van der Knaap, M., Muhoozi, L. I. and Othina, A. 2003. Improving fishery catch statistics for Lake Victoria. Aquat. Ecosyst. Health Manage., 6(3): 299–310.
Crapon de Caprona, M. D. and Fritzsch, B. 1984. Interspecific fertile hybrids of haplochromine Cichlidae (Teleostei) and their possible importance for speciation. Nether. J. Zool., 4: 503–538.
Frame Survey. 2008. A status report on the frame surveys 2000 to 2005, Jinja, Uganda: Lake Victoria Fisheries Organization.
Goudswaard, P. C. and Witte, F. 1997. The catfish fauna of Lake Victoria after the Nile perch upsurge. Env. Biol. Fish., 49: 21–43.
Goudswaard, P. C., Witte, F. and Katunzi, E. F. B. 2002. The tilapiine fish stock of lake Victoria before and after the Nile perch upsurge. J. Fish Biol., 60(4): 838–856.
Kudhongania, A. W. and Cordone, A. J. 1974. Batho-spatial distribution pattern and biomass estimation of the major demersal fishes in Lake Victoria. Afr. J. Hydrobiol. Fish., 3: 15–31.
Lowe-McConnell, R. H. 1955. The fecundity of tilapia species. E. Afri. Agri. J., 11: 45–52.
Lung'ayia, H. B. O., M'Harzi, A., Tackx, M., Gichuki, J. and Symoens, J. J. 2000. Phytoplankton community structure and environment in the Kenyan waters of Lake Victoria. Freshwat. Biol., 43: 529–543.
LVFO. 2004. LVFO Regional Plan of Action to Prevent, Deter and Eliminate Illegal, Unreported and Unregulated fishing on Lake Victoria and its Basin LVFO/FAO May 2004. ISBM: 9970-713-07-5
LVFO. 2007. LVFO Regional Plan of Action for the Management of the Fishing Capacity in Lake Victoria LVFO/FAO March 2007. ISBM: 9970-713-13X
Mhlanga, L., Day, J., Chimbari, M., Siziba, N. and Cronberg, G. 2006. Observations on limnological conditions associated with a fish kill of Oreochromis niloticus in Lake Chivero following collapse of an algal bloom. Afri. J. Ecol., 44: 199–208.
Mkumbo, O. C. 2002. Assessment and management of Nile perch (Lates niloticus L.) stocks in the Tanzanian waters of Lake Victoria, PhD Thesis Hull University, UK.
Mugidde, R., Gichuki, J., Rutagemwa, D., Ndawula, L. and Matovu, A. 2005. “Status of water quality and implications on fishery production”. In The State of the Fisheries Resources of Lake Victoria and their Management, 106–112. Jinja, Uganda: LVFO Secretariat. ISBN:9970-713-102
Mushi, V. E., Oenga, D. N. and Mwanja, W. W. 2005. “Meeting increasing demand for fish through development of aquaculture in the Lake Victoria Basin”. In The state of the fisheries Resources of Lake Victoria and their Management, 159–165. Jinja, Uganda: LVFO Secretariat. ISBN:9970-713-10-2
Njiru, M., Okeyo-Owuor, J. B., Muchiri, M. and Cowx, I. G. 2004. Shift in feeding ecology of Nile tilapia, Oreochromis niloticus (L.) in Lake Victoria, Kenya. Afr. J. Ecol., 41: 1–8.
Njiru, M., Waithaka, E., Muchiri, M., Van der Knaap, M. and Cowx, I. G. 2005. Exotic introductions to the fishery of Lake Victoria: What are the management options?. Lakes Reser.: Res. Manage., 10: 147–155.
Njiru, M., Ojuok, J. E., Okeyo-Owuor, J. B., Muchiri, M., Ntiba, M. J. and Cowx, I. G. 2006. Some biological aspects and life history strategies of Nile tilapia Oreochromis niloticus (L.) in Lake Victoria, Kenya. Afri. J. Ecol., 44: 1–8.
Njiru, M., Kazungu, J., Ngugi, C. C., Gichuki, J. and Muhoozi, L. 2008. An overview of the current status of Lake Victoria fishery: Opportunities, challenges and management strategies. Lakes Resev. Res. Manage, 13: 1–12.
Ntiba, M. J., Kudoja, W. M. and Mukasa, C. T. 2001. Management issues in the Lake Victoria watershed. Lakes Reser: Res. Manage., 6: 211–216.
Ochumba, P. B. O. 1990. Massive fish kills within the Nyanza Gulf of Lake Victoria, Kenya. Hydrobiologia, 208: 93–99.
Ogutu-Ohwayo, R. 1990. The decline of the native fishes of lakes Victoria and Kyoga (East Africa) and the impact of introduced species, especially the Nile perch, Lates niloticus and the Nile tilapia, Oreochroms niloticus. Environ. Biol. Fish, 27: 81–96.
SEDAWOG (Socio-economic data working group). 1999. The survey of Lake Victoria's fishers LVFRP/TECH/99/05. Jinja, Uganda
Seehausen, O., Van Alphen, J. J. M. and Van Witte, F. 1997. Cichlids diversity threatened by eutrophication that curbs sexual selection. Science, 277: 1808–11.
UNEP. 2006. Africa's Lakes: Atlas of Our Changing Environment. Division of Early Warning and Assessment (DEWA), Nairobi, Kenya: United Nations Environment Programme (UNEP). Earthprint.com ISBN: 92 807 2694
Van der Knaap, M., Ntiba, M. J. and Cowx, I. G. 2002. Key elements of fisheries management on Lake Victoria. Aquat. Ecosyst. Health Manage., 5: 245–254.
Welcomme, R. L. 1967. Observations on the biology of the introduced species of Tilapia in Lake Victoria. Rev. Zool. Bot. Afr., 76: 249–279.
Witte, F. and Van Densen, W. L. T. 1995. Fish Stocks and Fisheries of Lake Victoria. A Handbook for Field Observations, Cardigan, Britain: Samara Publishing.
Witte, F., Goudswaard, P. C., Katunzi, E. F. B., Mkumbo, O. C., Seehausen, O. and Wanink, J. H. 1999. “LakeVictoria's ecological changes and their relationships with the riparian societies”. In Ancient lakes: Their cultural and biological diversity, Edited by: Kawanabe, H., Coulter, G. W. and Roosevelt, A. C. 189–202. Belgium: Kenobi Productions.
Worthington, E. B. 1930. Observations on the temperature hydrogen-ion concentration and other physical conditions of Victoria and Albert Nyanza. Int. Rev. Ges. Hydrobiol. Hydrogr., 24: 328–357.
Yongo, E., Keizire, B. B. and Mbilinyi, H. G. 2005. “Socio-economic impacts of fish trade”. In The state of the fisheries Resources of Lake Victoria and their Management, 132–142. Jinja, Uganda: LVFO Secretariat. ISBN: 9970-713-10-2
Published
Issue
Section
License
Manuscripts must be original. They must not be published or be under consideration for publication elsewhere, in whole or in part. It is required that the lead author of accepted papers complete and sign the MSU Press AEHM Author Publishing Agreement and provide it to the publisher upon acceptance.
