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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Authors: | Dalmas Oyugi Oyugi David Matthew Harper Japheth Michemi Ntiba Seth Marande Kisia John Robert Britton |
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Institution: | (1) School of Biological Sciences, University of Nairobi, P.O. Box 30197, Nairobi, 00100, Kenya;(2) Centre for Conservation Ecology and Environmental Science, School of Applied Sciences, Bournemouth University, Poole, Dorset, BH12BB, UK;(3) Department of Biology, University of Leicester, University Road, Leicester, UK;(4) School of Veterinary Medicine, University of Nairobi, P.O. Box 30197, Nairobi, 00100, Kenya; |
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Abstract: | 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. |
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Keywords: | Oreochromis leucostictus Tilapia zillii Catch per unit effort Fishery catch Environmental change |
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