International Journal of Aquaculture, 2013, Vol.3, No.8, 35
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http://ija.sophiapublisher.com
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Table 1 Frequency (%) of species in total catches in Lake Sebakwe for the sampling period (2013)
Species
L.cylindricus M.pongolensis T.rendalii M.longirostris M.salmoides C.gariepinus B.imberi S.robustus
Frequency (% ) 20
8
0.3
0.1
60
1.0
0.2
0.4
vittatus
,
Castelnau 1861). The second most abundant
fish species were the
Labeo cylindricus (
Peters 1868):
This species is widely distributed throughout Africa
and consist of at least 80 species which comprise 16.
4%
of the African cyprinid ichthyofauna. It is a
benthopelagic species and occurs in both sediment-free
and sediment rich rocky biotopes, where it can be
abundant.
L.cylindricus
favors clear, running waters in
rocky habitats of small and large rivers, also found in
lakes and dams over rocky areas. This species is also
commercially important throughout the African
continent, having contributed significantly to various
fisheries (Skelton, 2001). It feeds on diatoms and
other small algae from rocks. It is a cryptic species
that hides under rocks and is most active at night
(
Gratwicke et al., 2003). It is a very small species
attaining a maximum length and mass of 25 cm standard
length and 0. 9 kg respectively (Skelton, 2001).
The third next frequent species was the
Marcusenius
pongolensis
(
Fowler, 1934): This fishis usually found
in main channels but lower catchments. It does not
enter still lagoons and backwaters in the lower
floodplains. It feeds primarily on benthic insects and
prefers white still waters. In Zimbabwe this is the first
record of the fish that we have found. It also prefers
clean white waters. The fourth most frequent species
was the Eastern bottlenose,
Mormyrus longirostris
(
Peters, 1852). This species is widespread but not
always numerous. It is a demersal and potamodromous
lives in caves and muddy areas, and it also hides
among weeds (Marshall, 2010). It prefers quite deep
waters with soft muddy bottoms and is rarely caught
in marshy areas. It is active mainly at night and it
breeds during the rainy season. It feeds on weeds and
insects but may also feed on small fishes, bloodworms,
crustaceans, mollusks and aquatic plants.
The next most abundant fish was the sharptooth
African catfish
Clarias gariepinus (
Burchell
,
1822
).
The African catfish
C. gariepinus
occurs in almost any
habitat but favors floodplains, large sluggish rivers,
lakes and dams. It can endure harsh conditions such as
high turbidity or desiccation and is frequently the last
or only inhabitant of diminishing pools of drying rivers
or lakes, where it may form burrows (Skeleton, 2001).
Further, as a predator, it is able to utilize a variety of
food items other than fish. The
Clarias
is well known
for its adaptability and its hardiness against adverse
environmental conditions, but tissue and organ
anomalies resulting from environmental stress can be
observed. These factors make them good indicators of
chronic environmental stress, enabling them to reflect
accumulative effects of both past and recent water
quality conditions (Avenant-Oldewage, 2001).
The next most abundant fish species was the redbreast
tilapia,
Tilapia rendalli
(
Boulenger, 1896) which is
generally an omnivorous, opportunistic feeder throughout
its life, with the adult tilapia shifting towards
herbivory as the primary feeding mode. Its natural
habitats are fresh water lakes and fresh water marshes
(
Skelton, 2001). The rendalli feeds on algae, plants,
small crustaceans, worms, and larvae, but prefers a
vegetation diet such as the thick growth of weed. It
can be found in perennial rivers, lakes and quiet places
with clay or sandy bottoms. In some places it has been
introduced into dams where the need to check the
growth of weeds is required. It is a tolerant of a broad
range of temperatures and salinity as well as high
levels of silt (Marshall, 2010). In this study we collected
the fish in the nets set close to the littoral shorelines
where there were dense growths of aquatic macrophytes.
The omnivorous and potamodromous The Spot-Tailed
Robber
Brycinus imberi
(
Peters, 1852) was also caught
but in fewer numbers and this fish favors freshwater
rivers and shallow clean waters.
The underlying pattern was that we sampled freshwater
fish that favour clean still white waters, a factor which
points to the nutrient status and quality of the water in
Lake Sebakwe. This brief survey found 8 species in a
Lake that has not received scientific attention but it is
hoped that it forms a baseline for future ichthyology
studies.
Acknowledgements
Special thanks go to the Department of Parks Lake Sebakwe for allowing us
to sample in their dam and Mr Joseph Chiwara and Ms Mercy Zimbizi of
Sebakwe Conservancy for technical assistance.
References
Avenant-Oldewage A., 2001, Protocol for the assessment of fish health based on