Ectoparasites infesting Nile tilapia (Oreochromis niloticus) and Haplochromines in Lake Mulehe, Kisoro District

Abstract

This study investigated the ectoparasitic occurrence, infestation levels and diversity in two economically important fish species; O. niloticus and Haplochromines on Lake Mulehe following recurring fish mass mortality incidences. A total of 132 fish specimen; 76 Haplochromines and 56 O.niloticus were examined for ectoparasites using standard parasitological procedures. Tetrahymena spp., Dactylogyrus spp.,Trichodina spp. and Neascus spp. were recovered from both O. niloticus and Haplochromis spp. Centrocestus spp. were identified only in Haplochromines. Neascus spp. (Diplostomidae) was the most dominant taxon with prevalence of 45% in O. niloticus and 88% in Haplochromis spp. The gills were the most parasitized organ. The study showed a significant relationship between fish size and only Neascus parasites intensities. The prevalence of parasites on small fishes was higher (18.9-20.9cm for O. niloticus and 6.9-9cm for Haplochromines) than on large hosts (>21cm and > 9cm for O. niloticus and Haplochromines respectively). In contrast, the intensity of parasites in large fishes were higher than on small individuals. The high mean intensities in large fishes were attributed to the increase in surface area for attachment and prolonged exposure to parasites. Higher parasite diversity was recorded among O niloticus individuals than Haplochromines and could be linked to territorial nature of O. niloticus that could have exposed individuals to diverse parasites. The high parasite diversity and infestation levels recorded in the present study may have contributed to the fish mass mortalities and disease outbreaks, hence need for periodic monitoring and implementation of biosecurity during restocking programmes. Further studies are recommended to investigate the influence of environmental dynamics on fish health in Lake Mulehe.