Thesis (M.Sc. (Aquaculture)) -- University of Limpopo, 2022 / The aim of this study was to provide baseline limnology data that can be used in the
management of small dams, Molepo Dam and Hout River Dam. Physico-chemical
parameters were assessed to determine the water quality and the effect of water level
fluctuations on water quality. Water temperature, pH, dissolved oxygen, turbidity,
electrical conductivity, nitrate, total phosphorus, total nitrogen and chlorophyll-a were
assessed during the dry season (May-Oct) and wet season (Nov-Apr). Physico chemical parameters showed seasonal variations with the exception of pH. The mean
total phosphorus (1.06 and 0.98 mg/L), total nitrogen (1.27 and 1.56 mg/L) and
chlorophyll-a (2.97 and 3.32 µg/L) were higher in the dry season than wet season in
Molepo Dam and Hout River Dam respectively. Water level fluctuations had a
significant effect on total nitrogen, total phosphorus and turbidity in Molepo Dam and
total nitrogen in Hout River Dam.
Plankton were used as indicators of water quality. Phytoplankton and zooplankton
were sampled using nets of 71 µm and 132 µm mesh respectively and identified to
genus and species at both Molepo Dam and Hout River Dam. Individual species,
number per litre for phytoplankton groups that contributed significantly in terms of
abundance were Microcystis aeruginosa and Oscillatoria sp. in both Molepo Dam and
Hout River Dam during the dry season months. The Shannon-Wiener diversity index
was high during the wet season in these small dams. The abundance of Cyanophyta
was greatest during the dry season followed by Desmids in Molepo Dam and Hout
River Dam. During the wet season, Bacillariophyta were not recorded for Hout River
Dam. The highest composition for Chlorophyta (15.4%) in Molepo Dam was recorded
during the wet season months. Phytoplankton abundance was highest in Molepo Dam
as compared to Hout River Dam throughout the sampling period. Zooplankton was
dominated by Cladocerans (Bosmina longirostris) in both small dams. This study
showed that plankton can be used as indicators of water quality. Zooplankton
communities were dominated by Bosmina longirostris which was present throughout
the sampling period possibly indicating clear water in Molepo Dam and Hout River
Dam. Copepoda were sub-dominant phyla mainly represented by Cycloid sp. which
are also indicators of clean water.
The study determined the abundance and composition of fish species and growth
parameters of the most abundant fish species (Oreochromis mossambicus) in the two
small dams. Scales were successfully used for the age determination of O.
mossambicus. The rings on the scales were validated as being true annuli by marginal
increment analysis which indicated that the distance between the last annuli and the
scale edge was shortest in the wet season months in Molepo Dam and Hout River
Dam. This is the time in which annulus formed. Annulus formation of O. mossambicus
at these small dams coincided with the onset of increased water temperature and
rainfall (increased water levels and increased water inflow into the dams) in this region.
Furthermore, the growth performance index (ϕ) of male O. mossambicus was higher
than that of female O. mossambicus in both Molepo Dam and Hout River Dam. The
study provides the first record of limnology baseline data of Molepo Dam and Hout
River Dam / National Research Foundation (NRF) and
Department of Agriculture, Forestry and Fisheries (DAFF)
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ul/oai:ulspace.ul.ac.za:10386/4156 |
| Date | January 2022 |
| Creators | Mphalo, Selaelo Jaqueline |
| Contributors | Theron, J., Moyo, N. A. G. |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | xiii, 89 leaves |
| Relation |
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