Spatial and temporal variations in densities of small fishes across different temporary floodplain types of the lower Okavango Delta, Botswana

  • N Siziba
  • MJ Chimbari
  • K Mosepele
  • H Masundire

Abstract

Small-sized and juvenile fishes as well as physicochemical water parameters in various primary, secondary and rarely flooded temporary floodplains of the Okavango Delta were assessed during the different hydrological phases of the 2009–2010 flooding season. Small fishes were sampled in the marginal zone of the floodplains using a throw-trap net and a suite of physicochemical properties were measured. Both physicochemical water quality parameters and densities of small fishes showed spatiotemporal variations across the temporary  floodplain types. Turbidity, dissolved oxygen, conductivity, woody debris and chlorophyll a were all highest in rarely flooded floodplains compared to both primary and secondary floodplains (ANOVA, p < 0.05). Fish from 38 fish taxa belonging to 11 families were identified and classified during the study. The fish families Cichlidae (dominated by tilapias), Poeciliidae (Aplocheilichthys spp.) and Cyprinidae (Barbus spp.), were the most abundant across the study floodplains. The poeciliids were most abundant in frequently flooded primary and secondary floodplains, whereas juvenile cichlids dominated in rarely flooded floodplains. During high floods the rarely flooded portions of the delta function as important nursery habitats for juvenile cichlids, implying that a significant reduction in flooding may have negative effects on the delta’s tilapia stocks due to reduced recruitment success.

Keywords: Cichlidae, Poeciliidae, rarely flooded floodplains, wetlands

African Journal of Aquatic Science 2011, 36(3): 309–320

Author Biographies

N Siziba
Okavango Research Institute, University of Botswana, Private Bag 285, Maun, Botswana
MJ Chimbari
Okavango Research Institute, University of Botswana, Private Bag 285, Maun, Botswana
K Mosepele
Okavango Research Institute, University of Botswana, Private Bag 285, Maun, Botswana
H Masundire
Department of Biological Sciences, University of Botswana, Private Bag 0022, Gaborone, Botswana
Section
Articles

Journal Identifiers


eISSN: 1727-9364
print ISSN: 1608-5914