Effects of Parasitism on Morphmetric Indices of Oreochromis niloticus (Linné, 1757) in a Tropical Reservoir

Abstract

Morphometric indices and parasitic infestation of Oreochromis niloticus (Linné, 1757) in Oba Reservoir were investigated between 2016 and 2018 using standard methods. Growth in total length and weight were higher in females than males, which could be traced to parental care in the fish species. Season had no effect on the growth and quantity captured. Growths of the fish were positively allometric. The correlation coefficient (r2) values in the two years (2016/2017, 2017/2018) for male (0.984 and 0.956), female (0.966 and 0.950) and combined sexes (0.961 and 0.959), were close to unity and showed that at least 95% of the data collated on length and body weight were able to fit into the regression line. Abundance and condition factor of the fish species were not related to seasons. The condition factor showed that, male lived a more robust life than the female. The helminthes parasites retrieved from the enteron comprised of two Acanthocephala Neoechinorhynchus rutili (Mueller, 1780), and Acanthocentius tilapiae and the metacercaria of a trematode Clinostomum tilapiae (Leidy, 1856). No parasite was found in the stomach, C. tilapiae were found in the buccal cavity; while acanthocephalans were found in the intestine. Prevalence of parasitic infestation values obtained in the two years was higher in females (23.40%) than in males (19.15%) and was higher in the dry seasons of the two years than the rainy seasons. Parasitaemia was observed not to have any significant effect on the total length and body weight of O. niloticus in Oba Reservoir.