Thesis (M.Sc. (Zoology)) --University Limpopo, 2013 / Major anthropogenic activities such as, mining, coal-fired power stations and
intensive agricultural practices in the upper catchment area of the Olifants River,
have a dramatic impact on the water quality downstream. As a result the river is
presently the third most polluted river in South Africa. The aim of this study was to
assess the impact of water and sediment quality on the health of Labeo rosae and
Schilbe intermedius. The aim was accomplished by applying the Fish Health
Assessment Index (HAI) which includes the Parasite Index (PI) at Flag Boshielo
Dam in the Middle Olifants River, Limpopo Province. This was achieved through;
assessing the water quality of the dam by determining the levels of physical and
chemical constituents in the water at three sampling sites, determining the
bioaccumulation of selected metals in the muscle tissue of the two fish species,
assessing the fish health (including the fish condition factor) and the fish parasites in
the dam by using the fish HAI and PI, and ascertaining the Human Health risk factor
upon consumption of fish contaminated with metals from the dam.
The water and sediment quality were seasonally sampled at three sites in the dam:
inflow, middle and wall. Dorsal muscle tissues from both fish species were collected
for metal bioaccumulation analyses. The water, sediment and fish muscle tissue
samples were analysed by an accredited laboratory by means of ICP-OES
spectrometry. For the fish health and parasites, ten fish per species were collected
seasonally (July 2009 to April 2010) by means of gill nets and examined at a field
laboratory using the HAI and PI protocol.
Generally the water quality of Flag Boshielo Dam was acceptable for aquatic
ecosystems according to the SAWQG with the exception of phosphorus and some
metals at the inflow area. The pH ranged between slightly acidic to alkaline values;
water temperature: 15°C to 26°C; water hardness medium soft, salinity within the
freshwater range; turbidity in the clear water range. The TDS and major ions (salts)
were acceptable for the duration of the study. The highest concentrations of nutrients
(specifically phosphorus) as well as metals (aluminium, cadmium, copper, iron and
lead) were recorded at the inflow area of the dam. The nutrients were very low
except the eutrophic range phosphorus concentrations recorded at the inflow
whereby, the Elands River may be an additional source of nutrients into Flag
Boshielo Dam. The metals that were recorded above TWQR are; aluminium,
cadmium, copper, iron and lead, of which were mostly recorded at the inflow.
However, statistically there was no significant difference among the three sampling
sites. The metal concentrations at the inflow were recorded only slightly higher than
the middle and the dam wall. The main source of the metals may be the water
coming from catchment area of the dam given the intensive agricultural activities
taking place between Loskop Dam and Flag Boshielo Dam.
Sediment and bioaccumulation: All the metals were recorded at higher
concentrations in the sediment than in the water and fish muscle tissue, except
antimony, selenium and strontium. The most abundant metals recorded in the
sediment were iron and aluminium. However, the concentrations above the TEL
were cadmium, nickel and zinc. The elevated metal concentrations in the sediment
are indicating that the metal load in the sediment of Flag Boshielo Dam could be a
potential risk for the aquatic biota if they become bioavailable. Antimony, selenium
and strontium metal concentrations were recorded at higher concentrations in the
muscle tissue of both fish species than in the sediment and water. Iron was the most
accumulated metal in the muscle tissue of both fish species. In terms of numbers,
more metals were recorded in the muscle tissue of S. intermedius than in L. rosae
however the metal concentrations were higher in the latter. This can be attributed to
their different trophic levels in the food chain; L. rosae is a primary consumer while
S. intermedius is a tertiary consumer. However, the metals that accumulated in the
fish muscle tissue were indicative of bio-availability of the toxic metals in the dam
and not water/sediment pollution.
According to a Human Health risk assessment (Chapter 3), metals that may have
risks upon consumption of L. rosae are; antimony, arsenic, chromium, iron and
vanadium; for S. intermedius are; antimony, chromium, iron, vanadium and arsenic
(in descending order). These metals may pose toxic and carcinogenic risks to
humans. Therefore, the rednose labeo (L. rosae) and to a lesser extend the silver
catfish (S. intermedius) fish species from Flag Boshielo Dam may not be suitable for
humans if consumed above 350 g per week.
Fish health and parasites: The Health Assessment Index (HAI) values of the two fish
species differed significantly with higher index values recorded for S. intermedius
than L. rosae. Besides the Parasite Index (PI), abnormal haematocrit readings, liver
conditions, skin lesions and clubbed gills are the necropsy anomalies that
contributed predominantly to the HAI. Overall, the PI contributed mostly to the total
HAI value.
The parasite load and therefore also the mean intensity, mean abundance and
prevalence of S. intermedius were higher during all seasons than that of L. rosae.
The dominant ectoparasites for both species were from the Class Monogenea and
the dominant endoparasites were nematodes. Out of 40 L. rosae sampled, 139
parasites were retrieved; five parasite species were ectoparasites and two
endoparasites. From the 40 S. intermedius sampled, 2473 parasites were retrieved,
from which two species (one genus) were ectoparasites and three species were
endoparasites.
The condition factor is used to compare the “condition”, “fatness” or wellbeing of fish
and it is based on the hypothesis that heavier fish of a particular length are in a
better physiological condition. The L. rosae had a better condition factor, recorded at
values less than (2) as compared to S. intermedius (>2).
The cause of the HAI necropsy anomalies may have been also from parasite load
other than the metals in the water and sediment. However, the HAI alone cannot be
used for metal pollution, unless it is done in conjunction with a histopathological
study of the tissues/organs. Therefore, the cause of the recorded anomalies from
both fish species is inconclusive. On the hand, fish can be used as bioindicators
because the accumulated metals in the fish tissues are indicative of the
bioavailability of metals in Flag Boshielo Dam.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ul/oai:ulspace.ul.ac.za:10386/1001 |
| Date | January 2013 |
| Creators | Kekana, Milicent Barileng |
| Contributors | Jooste, A., Luus-Powel, W. J., Addo-Bediako, A. |
| Publisher | University of Limpopo (Turfloop Campus) |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | vi, 113 leaves. |
| Relation |
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