The distribution and abundance of zooplankton in the fish cage sites of the Napoleon Gulf, Lake Victoria

Abstract

Lake Victoria is vulnerable to increasing eutrophication since the proliferation of cage fish farming in Uganda and this has rose concerns over water quality deterioration and changes in the ecological structure. A study was conducted on the distribution and abundance of zooplankton in the fish cage sites of Napoleon Gulf. The relative abundance and species diversity of the zooplankton was studied and the physicochemical parameters of the water at the cage sites determined The zooplankton community structure of the Napoleon Gulf was composed of the Rotifers, Copepods and Cladocerans. The rotifers were composed of seven genera including Synchaeta, Kellicotica, Keratella, Notholca, Tricocerca, Asplanchna and the Brachionus. The Copepods were comprised of four genera including Cyclopoids, Calanoids, harpaticoids and the Nauplii larvae and lastly the Cladocerans were composed of six genera: the Bosmina, Simocephallus, Daphnia, Ceriodaphnia, Moina and Diaphanosoma. The copepods were the most abundant among the three groups at the Gulf. The rotifers were the most diverse in terms of their generic composition amongst the copepods and the Cladocerans across all the sampling sites. There was no significant difference in the diversity of these zooplankton groups across all the sampling sites. This study recommended that SON fish farm to continue adhering to the best aquaculture management practices that are environmentally sustainable to allow many organisms like the zooplankton maintain their natural population densities, distribution, diversity and community structure and to continuously monitor the physicochemical parameter to keep them in check.