ECTOPARASTIC 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

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 Oreochromic niloticus. The skin and gills were examined for parasite prevalence, and intensity. Five mostly encountered parasite, 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 were 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 influence 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).

*Correspondence author

INTRODUCTION

Tilapias has 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 Aquacultural sector that is been focused to increase fish production. Aquaculture like intensive animal production imposes stressful factor 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 heavily cocoa plantation areas where chemicals are been applied throughout the year and there is likely water pollution occurrence, resulting from the chemical applied were examined. 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 Orechromics 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 gills filament 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 from 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. niloticusexamined 52 (86%) were parasitized with I. acuta showing the highest prevalene 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%) than the skin (37%) while Gyrodactylus vestators were found mostly on the skin. M cyprini which shows the least prevalence rate 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 whereit 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 apart from the well known problems facing farming, such fish meal, feed, seed supply and water management difficulties, environmental factors that influences 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 area close to chemical pollution either from nearby cocoa plantation, or industrial and house hold waste, though the containment substance (pesticides) may have harmful effect on the parasites, but such 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 endo parasites 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 support the observation in some of the ponds where the pH is as low as 5. Most of the ponds received domestic sewage causing high population 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 site and also differed between cultured fish of differences species collected from the farms. Infestation was much lower in farms with high management input than in the wild 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.