HISTOLOGICAL BASED BIOMONITORING: A BASELINE ECOTOXICOLOGICAL EVALUATION OF NEW-CALABAR RIVER USING CHRYSICHTHYS NIGRODIGITATUS. (Published)
The aim of this study was to evaluate the impact of environmental contaminants on gross anatomy (external and internal) and histopathologic biomarkers in liver, kidney and gills of African Silver Catfish (Chrysichthys Nigrodigitatus) collected from New Calabar River (NCR) in comparison to a reference site (African Aquaculture Centre, ARAC). NCR was chosen for this study because of its reported elevated levels of toxicants. For this study, chemical monitoring and bio-monitoring assessments were carried out in three sampling stations (Choba, Ogbogoro and Iwofe) of NCR. The chemical assessment involved EWQI assessment, sediment quality analysis, and heavy metals and PAH assessment. The histological bio-monitoring assessment involves the sampling of twenty table-sized fish harvested from the wild – the Choba station of NCR, which were compared with ten table-sized fishes of the same specie harvested from an aqua-cultured centre, ARAC, which has a controlled water quality system. EWQI was marginal, Sediment analysis showed slightly elevated level of PAH, Fish health Assessment Index (HAI) and fish biometric (CF) were worse in fishes harvested from NCR. Histopathological assessment was done in a qualitative and semi-quantitative scenario and fishes from NCR shows worse results as compared to those from ARAC. The qualitative assessment of target organs show alterations of target, which includes: Neurotic foci, vacuolation, melano-macrophageal centre and fatty changes in liver; intercellular haemorrage, intestinal oedema and melano-macrophageal centre in kidney and; telangiecstasia, epithelial lifting and hyperplasia in gills. Semi-quantitative histological assessment showed that NCR and ARAC had fish index values of 31.1 and 3.6 respectively. Following Man Whitney Test statistical analysis, significant differences (p<0.05) were noted between NCR and ARAC.