ABSTRACT

The impact of sub-lethal concentrations of glyphosate (an active ingredient in Roundup® herbicides) on growth, haematology and histology of Clarias gariepinus were evaluated. Uncontrolled discharge of glyphosate from agricultural farm land to aquaculture facilities necessitated the study. Sub-lethal concentrations (0.30mg/L, 0.50mg/L, 0.70mg/L and 1.40mg/L) examined were established after series of range finding tests. Weight in (g) and length measurement (cm) were taken on biweekly basis to monitor growth. Blood parameters analysed were Red Blood Cell (RBC), Haemoglobin content (Hb), Packed Cell Volume (PCV), White Blood Cell (WBC), Platelet (PLT), Mean Corpuscular Volume (MCV), Mean Corpuscular Haemoglobin (MCH) and Mean Corpuscular Haemoglobin Concentration (MCHC). Automated haematology analyser was used to determine the blood parameters. Histology of fish liver was studied among treatments. The liver was examined for lesions, oedema, lytic necrosis, focal necrosis, cloudy swelling, marked congestion and haemorrhages. The physico-chemical parameters monitored were temperature, pH, Dissolved Oxygen and Electrical Conductivity.  Thermometer, pH meter, dissolved oxygen meter and Electrical conductivity meter respectively were used. There was significant difference (P<0.05) in growth among the treatments. The best growth was recorded in 0.30mg/L while poorest growth was recorded in 1.40mg/L. There was significant difference in haematological parameters among the treatments (P<0.05). The concentration of 0.30mg/L showed lesions and vacuolization, 0.50mg/L multifocal necrosis and shrunk hepatic cells, 0.70 mg/L lytic necrosis and moderate haemorrhages and 1.4mg/L showed marked congestion, haemorrhages and necrosis of the hepatocyte while the control (0.00mg/L) showed normal central vein and the unaffected sinusoids. The findings in this study showed that 0.30mg/L to 1.40mg/L of the toxicants were harmful to Clarias gariepinus. The report therefore recommended examination of lower concentrations (<0.30mg/L) in future study to establish the limit beyond which glyphosate should not be allowed in aquaculture system.