The Effects of Raffia Palm Mesocarp on Haematological Parameters of Clarias gariepinus, a Common Niger Delta Wetland Fish

Indigenous people of the Niger Delta region in Nigeria depend on fisheries as the main protein source. The mesocarp of raffia palm is used by the indigenous people to stupefy and catch fishes. The mechanism of action of the raffia palm mesocarp is not well understood. Hence, this study investigated the effect of raffia palm mesocarp on the haematological properties of African catfish. Thirty two juveniles of C. gariepinus (eight in each treatment) were exposed to graded sub-lethal doses (0.4 – 0.6 g/l) of Raphia hookeri fruit mesocarp in 4 plastic aquaria. Renewal of test media was done every 48 hours for 10 days. Results show that increasing concentration of raffia led to decreasing red blood cells, platelets and haemoglobin levels while increasing white blood cells, eosinophils and monocytes. Water quality analysis results corroborated the haematological analysis. Alkalinity and pH increased, while dissolved oxygen decreased as the concentration of raffia palm fruit mesocarp increases. We therefore conclude that the mode of action of raffia palm fruit mesocarp involved increased alkalinity and decreased oxygen tension in the water which temporarily stupefies fishes for easy catch.