Management Implications of the Response of Two Tilapiine Cichlids to Long-Term Changes in Lake Level, Allodiversity and Exploitation in an Equatorial Lake
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The tilapiine cichlids Oreochromis leucostictus and Tilapia zillii were introduced into Lake Naivasha, Kenya, in 1956. Previous studies on data collected to 1987 revealed they were persistent following establishment, despite environmental variability and exploitation. Recent data, however, suggest this persistence is under threat as data indicate some significant declines in aspects of their abundance since 1999. The influence of changes in lake level, allodiversity and fishing effort on this decline was tested and showed that a decline in lake level was a significant causal factor. The recent change in allodiversity, with the establishment and dominance of Cyprinus carpio in the fishery, was not significant on the catch per unit effort of O. leucostictus but was on T. zillii. Since 1999, catches of tilapiines in the fishery have been independent of fishing effort, contrary to between 1975 and 1987, suggesting their management through application of fishery models may no longer be applicable. As it was anthropogenic-mediated lake level changes that were mainly responsible for their decline, then lake management should focus on sustainable water utilization that maximizes lake levels in accordance with the basin-wide water balance.
KeywordsOreochromis leucostictus Tilapia zillii Catch per unit effort Fishery catch Environmental change
This work was conducted under the Kenya Government Research Permit NCST 5/002/R/020-D to D. M. Harper and was undertaken with strong support from the Fisheries Department, the Kenya Marine and Fisheries Research Institute and the Water Resources Management Authority. Our appreciation is also due to The British Council for a Commonwealth Scholarship award to D. Oyugi to facilitate part of this work. Sponsors of funding also include the Earthwatch Institute (to 2007), the Darwin Initiative (logistical support of vehicles) and the British Council DelPHE project “Field IT” (2009-11). The authors would also like to sincerely thank Vincent I. Kinyua and George N. Morara for providing fishery data, Dominic Wambua for lake level data, George E. Owiti for laboratory working space and the entire “Lakes, Wetlands and People of East Africa’s Rift Valley” field team for their support in the sampling expeditions.
- Beveridge, M.C.M., and B.J. McAndrew. 2000. Tilapia: Biology and exploitations. Fish and Fisheries Series 25, 505 pp. Dordrecht: Kluwer Academic.Google Scholar
- Britton, J.R., D.M. Harper, and D.O. Oyugi. 2010. Is the fast growth of the introduced Micropterus salmoides in an equatorial lake explained by high water temperatures? Ecology of Freshwater Fish. doi: 10.1111/j.1600-0633.2010.00407.x.
- De Silva, S.S. 1985. Observations on the abundance of the exotic cichlid Sarotherodon mossambicus (Peters) in relation to fluctuations in the water-level in a man-made lake in Sri Lanka. Aquaculture and Fisheries Management 16: 265–272.Google Scholar
- Fryer, G., and T.D. Iles. 1972. The cichlid fishes of the Great Lakes of Africa: Their biology and evolution. Edinburgh: Oliver and Boyd. 641 pp.Google Scholar
- Harper, D.M., and K.M. Mavuti. 2004. Lake Naivasha, Kenya: Ecohydrology to guide the management of a tropical protected area. Ecohydrology and Hydrobiology 4: 287–305.Google Scholar
- Hickley, P., and D.M. Harper. 2002. Fish community and habitat changes in artificially stocked fishery of Lake Naivasha, Kenya. In Management and ecology of lake and reservoir fisheries, ed. I.G. Cowx, 242–254. Oxford: Blackwell Scientific Publications.Google Scholar
- Hickley, P., M. Muchiri, R.R. Boar, J.R. Britton, C. Adams, N. Gichuru, and D.M. Harper. 2004. Habitat degradation and subsequent fishery collapse in Lakes Naivasha and Baringo, Kenya. Ecohydrology and Hydrobiology 4: 503–517.Google Scholar
- Jul-Larsen, E., J. Kolding, J.R. Nielsen, R. Overa, and P.A.M. van Zwieten. 2003. Management, co-management or no management? Major dilemmas in southern African freshwater fisheries. Part 1. Synthesis report. FAO Fisheries Technical Paper No. 426/1. Rome: FAO.Google Scholar
- Kolding, J., and P.A.M. van Zwieten. 2006. Improving productivity in tropical lakes and reservoirs. Challenge program on water and food. Aquatic ecosystems and fisheries review series 1, 139 pp. Theme 3 of CPWF, C/o WorldFish Center, Cairo, Egypt, ISBN: 977-17-3087-8.Google Scholar
- Lowe-McConnell, R.H. 1982. Tilapias in fish communities. In The biology and culture of tilapias, eds. R.S.V Pullin and R.H. McConnell, 83–113. ICLARM conference proceedings 7. International Center for living Aquatic Resources Management, Manila.Google Scholar
- Muchiri, S.M., P. Hickley, D.M. Harper, and R. North. 1994. The potential for enhancing the fishery of Lake Naivasha, Kenya. In Rehabilitation of freshwater fisheries, ed. I.G. Cowx, 348–357. Oxford: Fishing News Book/Blackwell Science.Google Scholar
- Muchiri, S.M., P.J.B. Hart, and D.M. Harper. 1995. The persistence of two introduced tilapia species in Lake Naivasha Kenya in the face of environmental variability and fishing pressure. In The impact of species changes in African lakes, eds. T.J. Pitcher and P.J.B. Hart, 299–320. London: Chapman & Hall.Google Scholar
- Wootton, R.J. 1984. Introduction: Strategies and tactics in fish reproduction. In Fish reproduction: Strategies and tactics, eds. G.W. Potts and R.J. Wootton, 1–12. London: Academic Press.Google Scholar
- Zalewski, M., G.A. Janauer, and G. Jolankaj. 1997. Ecohydrology: A new paradigm for the sustainable use of aquatic resources. Conceptual Background, Working Hypotheses, Rationale and Scientific Guidelines for the Implementation of the IHP-V Projects 2.3/2.4. International Hydrological Programme UNESCO. Paris Technical Documents on Ecohydrology No. 7.Google Scholar