Evolutionary and Conservation Biology of Cichlid Fishes as Revealed by Faunal Remnants in Northern Lake Victoria

Lake Victoria until recently harbored the world’s second richest lacustrine fish assemblage, but it is now experiencing a mass extinction. Here we report on the current status of the endemic cichlid fishes from a preliminary biotic inventory conducted as part of limnological reconnaissance in Kenyan and Ugandan waters during 1989–1992. Sixty-two haplochromine taxa were recovered, half of them new. Some are local endemics, while others are more widely distributed, based on review of earlier collections. Comparison with data from 1982–1984 and 1988 suggests that some shoreline assemblages have been locally stable over the past decade. In addition to littoral rock and vegetation, four kinds of refugia for indigenous fishes are recognized: (1) schools of Rastrineobola, (2) benthic microbial mats in deep water, (3) satellite lakes, (4) the oxycline. Reconnaissance by remote operated vehicle (ROV) documented fish kills due to deoxygenation of the water column, indicating the risk of using the oxycline as a refugium. Several species formerly abundant in Lake Victoria were found only in satellite lakes, revealing the importance of these lakes in the conservation of indigenous species. Recent events in Lake Victoria shed light on mechanisms of speciation and mass extinction, insights relevant to conservation planning for the valuable remnants of the lake’s indigenous fauna. El lago Victoria albergaba, hasta no hace mucho, la segunda fauna lacustre mas rica del mundo pero ahora esta experimentado una extincion masiva. Nosotros, aqui reportamos el status presente de los peces ciclidos endemicos, de acuerdo a un inventario biotico preliminar realizado como parte de un reconocimiento limnologico en aguas de Kenya y Uganda durante 1989–1992. Fueron recuperadas sesenta y dos taxa de haplochrominas, la mitad de ellas nuevas. Algunas son endemicas locales, mientras que otras estan mas ampliamente distribuidas, segun revision de colecciones anteriores. Comparaciones con datos de 1982–84 y 1988 sugieren que algunos agrupaminetos costeros han sido estables localmmente en la decada pasada. Ademas de rocas y vegetacion litoral, se reconocieron cuatro tipos distintos de refugios para peces: (1) escuelas de Rastrineobola, (2) matas microbiales bentonicas en aguas profundas, (3) lagos satelites, (4) la oxiclina. Un reconocimiento con un vehiculo operado a control remoto (remote operated vehicle -ROV-) documento la muerte de peces debido a desoxigenacion de la columna de agua, indicando el riesgo de usar la oxiclina como refugio. Numerosas especies anteriormente abundantes en el lago Victoria fueron encontradas en lagos satelites, revelando la importancia de estos lagos en la conservacion de especies indigenas. Eventos recientes en el lago Victoria arrojaron luz sobre los mecanismos de especiacion y de extincion en masa, este conocimiento es relevante para el planeamiento de la conservacion de los valuables remanentes de la fauna indigena del lago.

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