Environmental Management

, Volume 52, Issue 6, pp 1386–1399 | Cite as

Variation in Assemblages of Small Fishes and Microcrustaceans After Inundation of Rarely Flooded Wetlands of the Lower Okavango Delta, Botswana

  • Nqobizitha SizibaEmail author
  • Moses J. Chimbari
  • Hillary Masundire
  • Ketlhatlogile Mosepele
  • Lars Ramberg


Water extraction from floodplain river systems may alter patterns of inundation of adjacent wetlands and lead to loss of aquatic biodiversity. Water reaching the Okavango Delta (Delta), Botswana, may decrease due to excessive water extraction and climate change. However, due to poor understanding of the link between inundation of wetlands and biological responses, it is difficult to assess the impacts of these future water developments on aquatic biota. Large floods from 2009 to 2011 inundated both rarely and frequently flooded wetlands in the Delta, creating an opportunity to examine the ecological significance of flooding of wetlands with widely differing hydrological characteristics. We studied the assemblages of small fishes and microcrustaceans, together with their trophic relationships, in temporary wetlands of the lower Delta. Densities of microcrustaceans in temporary wetlands were generally lower than previously recorded in these habitats. Microcrustacean density varied with wetland types and hydrological phase of inundation. High densities of microcrustaceans were recorded in the 2009 to 2010 flooding season after inundation of rarely flooded sites. Large numbers of small fishes were observed during this study. Community structure of small fishes differed significantly across the studied wetlands, with poeciliids predominant in frequently flooded wetlands and juvenile cichlids most abundant in rarely flooded wetlands (analysis of similarity, P < 0.05). Small fishes of <20 mm fed largely on microcrustaceans and may have led to low microcrustacean densities within the wetlands. This result matched our prediction that rarely flooded wetlands would be more productive; hence, they supported greater populations of microcrustaceans and cichlids, which are aggressive feeders. However, the predominance of microcrustaceans in the guts of small fishes (<20 mm) suggests that predation by fishes may also be an important regulatory mechanism of microcrustacean assemblages during large floods when inundated terrestrial patches of wetlands are highly accessible by fish. We predict that a decline in the amount of water reaching the Delta will negatively affect fish recruitment, particularly the cichlids that heavily exploited the rarely flooded wetlands. Cichlids are an important human food source, and their decline in fish catches will negatively affect livelihoods. Hence, priority in the management of the Delta’s ecological functioning should be centred on minimising natural water-flow modifications because any changes may be detrimental to fish-recruitment processes of the system.


Flooding frequency Microcrustaceans Juvenile fish Fish predation 



This study was funded by Carnegie–RISE through the Sub-Saharan Africa Water Resources Network. Staff at the University of Botswana Okavango Research Institute especially Thebe Kemosedile and Kaelo Makati for providing technical support during field sampling.


  1. Agostinho AA, Zalewski M (1995) The dependence of fish community structure and dynamics on floodplain and riparian ecotone zone in Parana River, Brazil. Hydrobiologia 303:141–148CrossRefGoogle Scholar
  2. Andersson L, Wilk J, Todd MC, Hughes DA, Earle A, Kniveton D et al (2006) Impact of climate change and development scenarios on flow patterns in the Okavango River. J Hydrol 331:43–57CrossRefGoogle Scholar
  3. Angermeier PL, Karr JR (1984) Relationships between woody debris and fish habitat in a small warm-water stream. Trans Am Microsc Soc 113:716–726Google Scholar
  4. Arcifa M (2000) Feeding habits of Chaoboridae larvae in a tropical Brazilian reservoir. Rev Bras Biol 60:591–597CrossRefGoogle Scholar
  5. Arthington AH, Balcombe SR (2011) Extreme flow variability and the “boom” and “bust” ecology of fish in arid zone floodplain rivers: a case history with implications for environmental flows, conservation and management. Ecohydrology 4:708–720CrossRefGoogle Scholar
  6. Ashton P (2000) Potential environmental impacts associated with the proposed abstraction of water from the Okavango River in Namibia. South Afr J Aquat Sci 25:175–182CrossRefGoogle Scholar
  7. Balarin J, Haller R (1982) The intensive culture of tilapia in tanks, raceways and cages. Recent Adv Aquac 1:265–355Google Scholar
  8. Balcombe SR, Bunn SE, Arthington AH, Fawcett JH, McKenzie-Smith FJ, Wright A (2007) Fish larvae, growth and biomass relationships in an Australian arid zone river: links between floodplains and waterholes. Freshw Biol 52:2385–2398CrossRefGoogle Scholar
  9. Bayley PB (1988) Factors affecting growth rates of young tropical floodplain fishes: seasonality and density-dependence. Environ Biol Fish 21:127–142CrossRefGoogle Scholar
  10. Bayley PB (1995) Understanding large river: floodplain ecosystems. Bioscience 45:153–158CrossRefGoogle Scholar
  11. Bonyongo MC (2004) The ecology of large herbivores in the Okavango Delta, Botswana. Doctoral thesis, University of Bristol, Bristol, UKGoogle Scholar
  12. Bonyongo M, Bredenkamp G, Veenendaal E (2000) Floodplain vegetation in the Nxaraga Lagoon area, Okavango Delta, Botswana. South Afr J Bot 66:15–21CrossRefGoogle Scholar
  13. Botrell HH, Duncan A, Gliwicz ZM, Grygierek E, Herzig A, Hillbright-Ilkowska A et al (1976) A review of some problems in zooplankton production studies. Nor J Zool 24:419–456Google Scholar
  14. Brooks JL, Dodson SI (1965) Predation, body size, and composition of plankton. Science 150:28–35CrossRefGoogle Scholar
  15. Clarke KR, Gorley RN (2006) Primer v6.1.5: User manual/tutorial. Plymouth Marine Laboratory, Plymouth, UKGoogle Scholar
  16. Coke M, Pott RM (1971) The Pongolo floodplain pans. Newsl Limnol Soc S Afr 16:20–26Google Scholar
  17. Cowx IG (2007) Interactions between fish and birds: Implications for management. Blackwell, OxfordGoogle Scholar
  18. Cushing DH (1972) The production cycle and the numbers of marine fish. Symp Zool Soc Lond 29:213–232Google Scholar
  19. Cushing D (1990) Plankton production and year-class strength in fish populations: an update of the match/mismatch hypothesis. Adv Mar Biol 26:249–293CrossRefGoogle Scholar
  20. de Graaf G (2003) Dynamics of floodplain fisheries in Bangladesh, results of 8 years fisheries monitoring in the compartmentalization pilot project. Fish Manag Ecol 10:191–199CrossRefGoogle Scholar
  21. Fernando C (1994) Zooplankton, fish and fisheries in tropical freshwaters. Hydrobiologia 272:105–123CrossRefGoogle Scholar
  22. Fernando CH (2002) A guide to tropical freshwater zooplankton: Identification, ecology and impact on fisheries. Bachuys, LeidenGoogle Scholar
  23. Fisher SJ, Brown ML, Willis DW (2001) Temporal food web variability in an upper Missouri River backwater: energy origination points and transfer mechanisms. Department of Wildlife and Fisheries Sciences. Ecol Freshw Fish 10:154–167CrossRefGoogle Scholar
  24. Gieske A (1996) Modelling outflow from the Jao/Boro river system in the Okavango Delta, Botswana. J Hydrol 193:214–239CrossRefGoogle Scholar
  25. Gilbert JJ, Burns CW (1999) Some observations on the diet of the backswimmer, Anisops wakefieldi (Hemiptera: Notonectidae). Hydrobiologia 412:111–118CrossRefGoogle Scholar
  26. Graves KG, Morrow JC (1998) Tube sampler for zooplankton. Prog Fish Cult 50:182–183CrossRefGoogle Scholar
  27. Harris JH, Gehrke PC (1994) Modelling the relationship between streamflow and population recruitment to manage freshwater fisheries. Agric Syst Inform Technol 72:393–407Google Scholar
  28. Hart RK, Calver MC, Dickman CR (2002) The index of relative importance: an alternative approach to reducing bias in descriptive studies of animal diet. Wildl Res 29:415–421CrossRefGoogle Scholar
  29. Hjort J (1914) Fluctuations in the great fisheries of northern Europe reviewed in the light of biological research. Rapp PV Réun Cons Int Explor Mer 20:1–13Google Scholar
  30. Hjort J (1926) Fluctuations in the year classes of important food fishes. ICES J Mar Sci 1:5–38CrossRefGoogle Scholar
  31. Høberg P, Lindholm M, Ramberg L, Hessen D (2002) Aquatic food web dynamics on a floodplain in the Okavango Delta, Botswana. Hydrobiologia 470:23–30CrossRefGoogle Scholar
  32. Horwood J, Cushing D, Wyatt T (2000) Planktonic determination of variability and sustainability of fisheries. J Plankton Res 22(7):1419–1422CrossRefGoogle Scholar
  33. Humphries P, King AJ, Koehn JD (1999) Fish, flows and floodplains: links between freshwater fishes and their environment in the Murray-Darling river system, Australia. Environ Biol Fish 56:129–151Google Scholar
  34. Hyslop E (1980) Stomach contents analysis—A review of methods and their application. J Fish Biol 17:411–429CrossRefGoogle Scholar
  35. Jones RI, Grey J, Sleep D, Arvola L (1999) Stable isotope analysis of zooplankton carbon nutrition in humic lakes. Oikos 86:97–104CrossRefGoogle Scholar
  36. Junk WJ (1999) The flood pulse concept of large rivers: learning from the tropics. Arch Hydrobiol 115(Suppl):261–280Google Scholar
  37. Junk WJ, Bayley PB, Sparks RE (1989) The flood pulse concept in river-floodplain systems. Can Special Publ Fish Aquat Sci 106:110–127Google Scholar
  38. Kawabata K, Urabe J (1998) Length–weight relationships of eight freshwater planktonic crustacean species in Japan. Freshw Biol 39:199–205CrossRefGoogle Scholar
  39. King A, Tonkin Z, Mahoney J (2009) Environmental flow enhances native fish spawning and recruitment in the Murray River, Australia. River Res Appl 25:1205–1218CrossRefGoogle Scholar
  40. Korovchinsky NM (1992) Sididae and Holopediidae: (Crustacea: Daphniiformes). Guides to the identification of the microinvertebrates of the continental waters of the world. Academic Publishers, HagueGoogle Scholar
  41. Kwak TJ (1988) Lateral movement and use of floodplain habitat by fishes of the Kankakee River, Illinois. Am Midl Nat 120(2):241–249CrossRefGoogle Scholar
  42. Lazzaro X (1991) Feeding convergence in South American and African zooplanktivorous cichlids Geophagus brasiliensis and Tilapia rendalli. Environ Biol Fish 31:283–293CrossRefGoogle Scholar
  43. Lewis WM Jr (1977) Feeding selectivity of a tropical Chaoborus population. Freshw Biol 7:311–325CrossRefGoogle Scholar
  44. Lewis WM Jr, Hamilton SK, Rodrıguez M, Saunders JF III, Lasi MA (2001) Foodweb analysis of the Orinoco floodplain based on production estimates and stable isotope data. J North Am Benthol Soc 20:241–254CrossRefGoogle Scholar
  45. Lindholm M, Hessen D (2007a) Zooplankton succession on seasonal floodplains: surfing on a wave of food. Hydrobiologia 592:95–104CrossRefGoogle Scholar
  46. Lindholm M, Hessen DO (2007b) Competition and niche partitioning in a floodplain ecosystem: a cladoceran community squeezed between fish and invertebrate predation. Afr Zool 42:158–164CrossRefGoogle Scholar
  47. Lindholm M, Hessen D, Mosepele K, Wolski P (2007) Food webs and energy fluxes on a seasonal floodplain: the influence of flood size. Wetlands 27:775–784CrossRefGoogle Scholar
  48. Lowe-McConnell RH (1979) Ecological aspects of seasonality in fishes of tropical waters. In: Miller PJ (ed) Fish phenology. London Academic Press, London, pp 219–241Google Scholar
  49. Lowe-McConnell RH (1987) Ecological studies in tropical fish communities. Cambridge University Press, CambridgeCrossRefGoogle Scholar
  50. Masundire HM (1994) Mean individual dry weight and length–weight regressions of some zooplankton of Lake Kariba. Hydrobiologia 272:231–238CrossRefGoogle Scholar
  51. Masundire HM (1997) Spatial and temporal variations in the composition and density of crustacean plankton in the five basins of Lake Kariba, Zambia-Zimbabwe. J Plankton Res 19:43–62CrossRefGoogle Scholar
  52. May RM (1974) Larval mortality in marine fishes and the critical period concept. In: Blaxter JH (ed) The early history of fish. Springer, New YorkGoogle Scholar
  53. Mbaiwa JE (2004) Causes and possible solutions to water resource conflicts in the Okavango River Basin: the case of Angola, Namibia and Botswana. Phys Chem Earth 29:1319–1326CrossRefGoogle Scholar
  54. McCarthy J, Gumbricht T, McCarthy TS (2005) Ecoregion classification in the Okavango Delta, Botswana from multitemporal remote sensing. Int J Remote Sens 26:4339–4357CrossRefGoogle Scholar
  55. McLachlan S (1971) The rate of nutrient release from grass and dung following immersion in lake water. Hydrobiologia 37:521–530CrossRefGoogle Scholar
  56. Medeiros ESF, Arthington AH (2008) The importance of zooplankton in the diets of three native fish species in floodplain waterholes of a dryland river, the Macintyre River, Australia. Hydrobiologia 614:19–31CrossRefGoogle Scholar
  57. Mehner T, Thiel R (1999) A review of predation impact by 0 + fish on zooplankton in fresh and brackish waters of the temperate northern hemisphere. Environ Biol Fish 56:169–181CrossRefGoogle Scholar
  58. Mendelsohn JM, Vanderpost C, Ramberg L, Murray-Hudson M, Wolski P, Mosopele K (2010) Okavango Delta: floods of life. Research and Information Services of Namibia, WindhoekGoogle Scholar
  59. Merron GS (1991) The ecology and management of the fishes of the Okavango Delta, Botswana, with particular reference to the role of the seasonal flood. Doctoral thesis, Rhodes University, South AfricaGoogle Scholar
  60. Merron GS (1998) Pack-hunting in two species of catfish, Clavias gariepinus and C. ngamensis, in the Okavango Delta, Botswana. J Fish Biol 43(4):575–584Google Scholar
  61. Merron SG, Bruton NM (1995) Community ecology and conservation of the fishes of the Okavango Delta, Botswana. Environ Biol Fish 43:109–119CrossRefGoogle Scholar
  62. Meschiatti A, Arcifa M (2002) Early life stages of fish and the relationships with zooplankton in a tropical Brazilian reservoir: lake Monte Alegre. Brazilian J Biol 62:41–50CrossRefGoogle Scholar
  63. Meyer T (1999) Ecological mappings in the research area of the HOORC, Okavango Delta, Botswana. Master’s thesis, Anhalt University, Köthen, GermanyGoogle Scholar
  64. Mhlanga L (2004) The diet of five cichlid fish species from Lake Kariba, Zimbabwe. Trans Zimb Sci Assoc 74:16–21Google Scholar
  65. Milzow C, Burg V, Kinzelbach W (2010) Estimating future ecoregion distributions within the Okavango Delta Wetlands based on hydrological simulations and future climate and development scenarios. J Hydrol 381:89–100CrossRefGoogle Scholar
  66. Moriarty C, Moriarty D (1973) Quantitative estimation of the daily ingestion of phytoplankton by Tilapia nilotica and Haplochromis nigripennis in Lake George, Uganda. J Zool 171:18–23Google Scholar
  67. Mosepele K (2000) Preliminary length based stock assessment of the main exploited stocks of the Okavango delta fishery. MPhil thesis, University of Bergen, Bergen, NorwayGoogle Scholar
  68. Mosepele K, Moyle P, Merron G, Purkey D, Mosepele B (2009) Fish, floods, and ecosystem engineers: aquatic conservation in the Okavango Delta, Botswana. Bioscience 59:53–64CrossRefGoogle Scholar
  69. Munro AD (1990) Tropical freshwater fishes. In: Munro AD, Scott AP, Lam TJ (eds) Reproductive seasonality in teleosts: environmental influences. CRC Press, Boca Raton, pp 145–239Google Scholar
  70. Murray-Hudson M, Wolski P, Ringrose S (2006) Scenarios of the impact of local and upstream changes in climate and water use on hydro-ecology in the Okavango Delta, Botswana. J Hydrol 331:73–84CrossRefGoogle Scholar
  71. Murray-Hudson M, Combs F, Wolski P, Brown MT (2011) A vegetation-based hierarchical classification for seasonally pulsed floodplains in the Okavango Delta, Botswana. Afr J Aquat Sci 36(3):223–234CrossRefGoogle Scholar
  72. O’Brien WJ (1979) The predator-prey interaction of planktivorous fish and zooplankton: recent research with planktivorous fish and their zooplankton prey shows the evolutionary thrust and parry of the predator-prey relationship. Am Sci 67:572–581Google Scholar
  73. Orlova-Bienkowskaja M (2001) Cladocera: Anomopoda, Daphniidae: Genus Simocephalus. Backhuys, LeidenGoogle Scholar
  74. Paxinos R, Mitchell JG (2000) A rapid Utermöhl method for estimating algal numbers. J Plankton Res 22:2255–2262CrossRefGoogle Scholar
  75. Pelicice FM, Agostinho AA, Thomaz SM (2005) Fish assemblages associated with Egeria in a tropical reservoir: investigating the effects of plant biomass and deil period. Acta Oecologica 27:9–16CrossRefGoogle Scholar
  76. Pinkas L, Oliphant MS, Inverson ILK (1971) Food habits of albacore, bluefin tuna and bonito in Californian waters. California Department of Fish and Game Fisheries. Fish Bull 152:11–105Google Scholar
  77. Power ME, Sun A, Parker G, Dietrich WE, Wootton JT (1995) Hydraulic food-chain models. Bioscience 45(3):159–167CrossRefGoogle Scholar
  78. Pusey BJ, Arthington AH (2003) Importance of the riparian zone to the conservation and management of freshwater fish: a review. Mar Freshw Res 54:1–16CrossRefGoogle Scholar
  79. Ramberg L, Hancock P, Lindholm M, Meyer T, Ringrose S, Sliva J et al (2006) Species diversity of the Okavango Delta, Botswana. Aquat Sci 68:310–337CrossRefGoogle Scholar
  80. Ramberg L, Lindholm M, Hessen OD, Murray-Hudson M, Bonyongo C, Heinl M et al (2010) Aquatic ecosystem responses to fire and flood size in the Okavango Delta: observations from the seasonal floodplains. Wetlands Ecol Manag 18(5):587–595CrossRefGoogle Scholar
  81. Rolls RJ, Wilson GG (2010) Spatial and temporal patterns in fish assemblages following an artificially extended floodplain inundation event, northern Murray-Darling Basin, Australia. Environ Manag 45:822–833CrossRefGoogle Scholar
  82. Shurin JB, Allen EG (2001) Effects of competition, predation, and dispersal on species richness at local and regional scales. Am Nat 158:624–637CrossRefGoogle Scholar
  83. Siziba N, Chimbari M, Mosepele K, Masundire H (2011a) Spatial and temporal variations in densities of small fishes across different temporary floodplain types of the lower Okavango Delta, Botswana. Afr J Aquat Sci 36:309–320CrossRefGoogle Scholar
  84. Siziba N, Chimbari MJ, Masundire H, Mosepele K (2011b) Spatial and temporal variations of microinvertebrates across temporary floodplains of the lower Okavango Delta, Botswana. Phys Chem Earth 36:939–948CrossRefGoogle Scholar
  85. Siziba N, Chimbari MJ, Masundire H, Mosepele K (2011c) Spatial variations of microinvertebrates across different microhabitats of temporary floodplains of lower Okavango Delta, Botswana. Afr J Ecol 50:43–52CrossRefGoogle Scholar
  86. Skelton P (2001) A complete guide to the freshwater fishes of southern Africa. Struik, Cape TownGoogle Scholar
  87. Smirnov NN (1992) The macrothricidae of the world. Guides to the identification of the microinvertebrates of the continental waters of the world. SPB Academic, The HagueGoogle Scholar
  88. Smirnov NN (1996) Cladocera: The Chydorinae and Sayciinae (Chydoridae) of the world. SPB Academic, AmsterdamGoogle Scholar
  89. Sokal RR, Rohlf FJ (1991) Biometry: the principles and practice of statistics in biological research. Freeman, New YorkGoogle Scholar
  90. Sparks RE (1995) Need for ecosystem management of large rivers and their floodplains. Bioscience 45:168–182CrossRefGoogle Scholar
  91. Trippel E, Chambers R (1997) The early life history of fishes and its role in recruitment processes. In: Chambers RC, Trippel EA (eds) Early life history and recruitment in fish populations. Chapman and Hall, London, pp 21–32Google Scholar
  92. Wallace KM, Leslie AJ (2008) Diet of the Nile crocodile (Crocodylus niloticus) in the Okavango Delta, Botswana. J Herpetol 42(2):361–368CrossRefGoogle Scholar
  93. Ward JV (1998) Riverine landscapes: biodiversity patterns, disturbance regimes, and aquatic conservation. Biol Conserv 83:269–278CrossRefGoogle Scholar
  94. Welcomme RL (1979) Fisheries ecology of floodplain rivers. Longman, LondonGoogle Scholar
  95. Welcomme RL (2001) Inland fisheries: ecology and management. Blackwell Science, OxfordCrossRefGoogle Scholar
  96. Winemiller KO (1996) Factors driving temporal and spatial variation in aquatic floodplain food webs. In: Polis GA, Winemiller KO (eds) Food webs: Integration of patterns and dynamics. Chapman and Hall, New York, pp 298–312CrossRefGoogle Scholar
  97. Winemiller K, Kelso-Winemiller L (2003) Food habits of tilapiine cichlids of the Upper Zambezi River and floodplain during the descending phase of the hydrologic cycle. J Fish Biol 63:120–128CrossRefGoogle Scholar
  98. Wolski P, Murray-Hudson M. (2006) Reconstruction of 1989-2005 inundation history in the Okavango Delta from archival LandSat TM imagery. Globewetlands Symposium, ESA-ESRIN, Frascati, Rome, Italy, October 19–20, 2006Google Scholar
  99. Zeug S, Winemiller K (2008) Relationships between hydrology, spatial heterogeneity and fish recruitment dynamics in a temperate floodplain river. River Res Appl 24:90–102CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media New York 2013

Authors and Affiliations

  • Nqobizitha Siziba
    • 1
    • 4
    Email author
  • Moses J. Chimbari
    • 3
  • Hillary Masundire
    • 2
  • Ketlhatlogile Mosepele
    • 1
  • Lars Ramberg
    • 1
  1. 1.Okavango Research InstituteUniversity of BotswanaMaunBotswana
  2. 2.Department of Biological SciencesUniversity of BotswanaGaboroneBotswana
  3. 3.University of KwaZulu-NatalDurbanSouth Africa
  4. 4.School of Natural Sciences and MathematicsChinhoyi University of TechnologyChinhoyiZimbabwe

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