Ectoparasitic Studies of Pond Cultured and Wild Tilapias in Major Cocoa
Producing Area of Nigeria
Bello-Olusoji, O.A.1, Aderiye B.K.1, Borede A.A.1 and Oyekanmi F.B.2
1. Fisheries and Wildlife Department, Federal University of Technology, P.M.B. 704,
Akure, Nigeria
Futa.oauife.edu.ng
2.Osun State College of Education, P.M.B, 5089, Ilesa, Nigeria
ABSTRACT
A total of 218 pond cultured and wild tilapias were collected from fish farms and the wild
(streams and rivers) located within in the major cocoa producing area where chemical
application is constant. The tilapia population consisted of two main species, Tilapias
melanopleura and Oreochromis niloticus. The skin and gills were examined for parasite
prevalence, and intensity. The five most encountered parasites were Tricodina acuta
(45.5%), Ichthyophithrins mutiflies (33.0%), Myxobulus cyprim (16.6%), Trypanosoma
tincae (1.6%), Gyrodactylus vastator (3.3%). The intensity of the parasites differed
markedly. All examined pond cultured tilapias were infected by T. acuta, having the highest
intensity (2.9) per fish, than wild tilapias. The results showed that the type of culture system
influences the prevalence and intensity of parasites in tilapia. Resistance of wild tilapias
were higher, while infestation in pond cultured tilapias was high. Correlation between the
two was positive and low (r=0.42).
INTRODUCTION
Tilapias have a wide geographical distribution, available in virtually all available water
bodies in Nigeria. It is valuable food fish, and commercially cultured in Nigeria.
Disease is one of the major detrimental factors in the aquacultural sector that is been focused
upon to increase fish production. Aquaculture, like intensive animal production, imposes
stressful factors, which may predispose to disease. Marquardt and Demarre (1985) reported
that parasitic disease of livestock and fishes reduces the amount of food available to people
everywhere. It is important to investigate the relationship between the environmental factors,
as it affects the parasites which causes fish diseases and their effects on fish production and
quality. Though Landsberg (1989) reported that factors influencing parasitic infections are
manifold and form a complex web of inter relationships between the pollution of surface
water by a wide range of chemicals and disease in natural fish populations, and the processes
involved. This represents an important but at present under developed field of scientific
research and fisheries management (Svobodova et al. 1993).
In this study some ectoparasites of cultured fishes, tilapias & wild tilapias in heavy cocoa
plantation areas where chemicals have been applied throughout the year and water pollution
occurrence is likely, resulting from the chemicals applied, were examined in order to
compare the prevalence and intensity of ectoparasites on the two groups of fishes.
MATERIALS & METHODS
Pond-cultured tilapias were collected from government, institutional and private commercial
farms while wild tilapias were collected from the major rivers, Ala and Ogbese. They are
Tilapia melanopleura and Orechromis niloticus. Collections were grouped into two
categories viz: sexually matured adult (>10 cm) (SM) and 12 young adult (<10 cm).
Thrice, fish were examined within 24 hours of collection. The external surface was
examined macroscopically for ectoparasites. Scraped mucus from the skin and gills were
examined on a slide under a compound microscope for parasites and the scales were removed
and the skin was swabbed with 70% alcohol. Smears were also made from the gills and the
skin using Convoy and Herman’s method (1970). Later the gill filaments were removed and
separated into a beaker filled with water, this was allowed to settle and the sediment was
examined using a compound microscope (400x Mag).
ANOVA was employed in the statistical evaluation of data at 0.01 and 0.05 levels of
significance. A comparison of means was based on Duncan’s multiple range test.
RESULTS AND DISCUSSION
A total of 218 fish were examined for ectoparasites. 110 tilapias from fish farms and 108
tilapias from the wild. These comprised of 60 T. melanopleura from each sector, 50 cultured
O. niloticus and 48 wild O. niloticus. Five major species of parasites belonging to protozoa,
monogenea and copepoda were observed (Table 1). All fish examined were carriers of more
than one parasite/cultured parasite. O. niloticus has the highest parasitic infestation followed
by cultured T. milanopleura while young T. melanopleura from the wild has the lowest
degree of infestation. Out of 60 O. niloticus examined 52 (86%) were parasitized with I.
acuta showing the highest prevalence on that stages. Infection was followed by cultured T.
melanopleura (adult, 72%) with T. acuta having the highest prevalence. This was also
recorded for with young T. melanepleura having the lowest rate of parasitic infection. I.
acuta were mostly recovered from the gills (63%) rather than the skin (37%) while
Gyrodactylus vestators were found mostly on the skin. M cyprini, which shows the least
prevalence occurred on both parts, that is on the skin and gills except in young O. niloticus
where it occurred on the gills only. I. tincae also was observed to be present on the skin and
gills except in wild O. niloticus where it occurred only on the skin.
The results indicated that the occurrence of T. acuta is significant (P<0.05) on the fish
species. While I. multifilis is significant (P<0.05) on the body region. It was observed in
these ponds that, apart from the well known problems facing farming, such fish meal, feed,
seed supply and water management difficulties, environmental factors that influence disease
spreading in fish farms should be considered. Considerations for the effect in the nearest
features will automatically increase fish production. These ponds are supplied by streams or
spring water, but they are located in areas close to chemical pollution either from nearby
cocoa plantations, or industrial and household waste. Although the containment substance
(pesticides) may have harmful effects on the parasites, fish that are weakened by parasite
infestation may be more sensitive to the toxic effects of these chemicals or substances. Khan
and Thuln (1991) observed that the degree of pathogenic activity exerted by ecto- and
endoparasites living on the body surfaces, land, or in internal organs of fish can be influenced
by water pollution.
Svobodova et al. (1993) identified some conditional dependencies on organic and other
pollution of the aquatic environment for a number of fish protozooses, such as poor water
quality causing gills invasion with Cryptopia brachialis. Reduced pH (e.g. to 5.6) and
unsuitable breeding conditions can contribute to an outbreak of ichthyobodosis. This
supports the observation in some of the ponds where the pH is as low as 5. Most of the
ponds received domestic sewage, causing high populations of trichodinas.
CONCLUSION
The intensities of I. acuta, I. multifiles, G. vestator, M. cyprini and I. tincae differed markedly
between fish of the same species collected from different sites and also differed between
cultured fish of different species collected from the farms. Infestation was much lower in
farms with high management input than in the wild or in those with low management input.
It was more pronounced on O. niloticus, T. melanopleura and C. gariepinus collected from
Federal University of Technology, Akure, with low management input compared to those
collected from Ondo State Agricultural Development Project, Akure, with high management
input.
Table 1. Prevalences and Mean Intensities of Infection of Parasites on Cultured and Wild Tilapia.
Pond-cultured Tilapia
Species
T. melanopleura
Wild Tilapia
O. niloticus
T. melanopleura
O. niloticus
Size (Group)
Adult (>10 cm)
Young (<10 cm)
Adult (>10 cm)
Young (<10 cm)
Adult (>10 cm)
Young (<10 cm)
Adult (>10 cm)
Young (<10 cm)
No. examined
30
30
25
25
30
30
24
24
Parasites
T. acuta
91.
30.0
42.0
44.0
96.0
52.0
61.5
30.0
62.3
35.0
46.0
25.9
78.8
35.0
40.4
25.0
42.3
54.6
52.0
24.6
5.7
32.6
14.1
57.7
42.6
35.3
30.5
54.7
259.0
46.2
18.0
10.0
28.7
22.0
5.4
22.0
34.2
21.0
28.0
16.0
12.3
19.0
19.7
10.9
21.2
25.0
1
I. multiflis
71.
5
M. Cypini
30.
2
I. tincae
2.0
1.0
4.0
1.0
2.0
1.0
2.0
1.0
2.0
1.0
2.0
2.0
-
-
G. vastator
22.
17.0
11.0
3.0
15.0
10.0
-
-
1.0
1.0
-
-
1.0
-
0