International Journal of Aquaculture, 2015, Vol.5, No.4 1
-
5
4
transmitted into ponds causing an outbreak.
External parasites might be transmitted from infested
brood stock from pond to pond through either direct or
in direct transition when their fingerlings are used to
stock un-infected ponds (Bondad-Reantaso et al.,
2005; Murray & Peeler, 2005). There was no clear
relationship observed between the intensity of
Monogeneans, Trichodina
spp. and
Ichthyopthirius
in
the gill and skin mucus samples and temperature in
the pond water.
There was no intense variability in both prevalence
and intensity of ecto-parasites identified among gills,
fin and skin mucus samples from the
O. niloticus
.
Several works on
Trichodina
have reported that the
organ possesses sucking valves in some species, but
hooks are always present. Skin or gill damage from
hooks on the opishaptor serves as entry for
opportunistic disease causing organisms. According to
Klinger (2002), infected fishes lose appetite and scales
in areas where flukes are attached. Infected gills may
look swollen and pale and have increased respiratory
activity (Klinger & Floyd, 2002; Whittington et al.,
2000). This might confirm the present outcome in
which the
Trichodina
were more prevalent in the gill
than other ecto-parasites.
4 Materials and Methods
Data for this study was collected from Water Research
Institute in Tamale, Northern Ghana.The size of
concrete ponds in which samples were collected was
5.0 m ×5.3 m and 5.5 m ×5.7 m with water depth of
1m. The study was conducted within six months
(November 2013 – April 2014). A total number of 240
Oreochromis niloticus
were collected from concrete
ponds at Water Research Institute. They were grouped
into adult and fingerlings; fingerlings with a total
length of 5-11 cm and body weight of 11-12 g and
adult with total length of 12 cm – 18cm and weight of
30 g – 100 g. Fish was sent alive in large plastic bags
containing pond water to sustain the fish prior to the
Laboratory for examination at Water Research Institute
Tamale, Ghana.
Samples of fish were taken monthly. The measurement
of the total length was done from the tip of the snout
to the tip of the caudal fin using a metric measuring
board and recorded to the nearest 0.1 cm. The weight
of individual fish was taken by singly placing each
fish in the pan of the weighing scale. The value for the
weight displayed on the screen was recorded to the
nearest 0.1 g.
In the laboratory the skin, the skin mucus, the scales,
the fins and the gills which form the external parts of
the fish were examined for parasites using magnified
hand lens. The fishes were examined according to the
method described by Paperna (1996). Critica
l
examination was done using light microscope at 40×–
100×for identification. A fish parasitology guide was
used for to aid identification of each specimen
examined and compared to the plates as described by
Barker et al (2000).
The data were analysed for the prevalence and mean
intensity. The prevalence (%) of the ecto-parasites was
estimated as the ratio between the number of infested
fish and the number of examined fish expressed in
percentages.
The mean intensity (M.I) was determined as the ratio
between the total number of parasites in a sample and
the number of infested fish in a sample.
Data obtained from the field and the laboratory results
was analysed using statistical tools and descriptions
from
Microsoft Excel 2013 and Statistica 8.1.
5 Conclusion
Trichodina spp.,
Monogeneans and
Ichthyophthirius
multifilis
were the ecto-parasites encountered during
the study. The prevalence and intensity of the
ecto-parasites were low. The effects of slightly acidic
pond water on ecto-parasite in fish could be
ambiguous, thus requiring concise inferences from
further studies. The occurrence of these ecto-parasites
had no clear relationship with physico-chemical
parameters and it could therefore be as a result of
accidental consequences. Both environmental factors
and routine management practices carried out on the
ponds have no vibrant relationship with the prevalence
levels or the intensities of the ecto-parasites.
