Parasitological Profiles of Fish from Petroleum-Impacted Freshwater Ecosystems in Delta State, Nigeria

Abstract

This study assessed the parasitological profiles of fish from petroleum-impacted freshwater ecosystems in Delta State, Nigeria, and examined spatial associations between petroleum contamination and parasite burden. A total of 300 fish representing six freshwater species were collected from five sampling stations and examined for ectoparasites and endoparasites using standard parasitological procedures. Water samples were analysed for total petroleum hydrocarbons (TPH) and total polycyclic aromatic hydrocarbons (PAHs), while parasite prevalence, mean intensity and mean abundance were determined. Overall, 126 fish were infected, giving a prevalence of 42.0%. Clarias gariepinus had the highest prevalence (53.3%), whereas Chrysichthys nigrodigitatus had the lowest (30.0%). A total of 218 parasites were recovered; nematodes were most abundant (31.2%), followed by trematodes, cestodes, acanthocephalans and protozoans. The gastrointestinal tract accounted for 48.2% of recovered parasites. Parasite prevalence varied spatially from 26.7% at S1 to 58.3% at S4, and mean intensity ranged from 1.38 to 2.09. TPH concentrations ranged from 2.84 ± 0.31 to 14.72 ± 1.06 mg/L, with S4 recording the highest petroleum burden and parasitological indices. Petroleum contamination showed positive associations with parasite prevalence and mean intensity. These findings indicate substantial spatial variation in fish parasitism and support integrating parasitological indicators with petroleum monitoring in freshwater ecosystem assessment.