Impact of Tetrapleura tetraptera aqueous extract on water quality variables and hatching success of Clarias gariepinus

The use of ichthyotoxic plants to stupefy fishes is a common fishery practice in tropical regions despite the superiority of modern netting materials and prohibition by law. Though these plants derivatives are believed to be nontoxic compared to their synthetic counterparts, they may contain a number of harmful ingredients or their secondary metabolites may have deleterious side effects. This study investigated the physico-chemical parameters of water media exposed to varying concentrations of Aidan, Tetrapleura tetraptera aqueous extract and their implications for the hatching success of Clarias gariepinus. Mature leaves of T. tetraptera were harvested, verified, crushed, and soaked in 6 liters of borehole water to obtain the stock solution. Serial dilutions were prepared from this solution into six treatments with the following concentrations: 75, 50, 25, 12.5, 6.25, and 3.125 ml/l designated as T1 to T6 respectively. The seventh treatment served as the control (without extract). Fertilized egg masses of C. gariepinus were exposed to the different concentrations of the aqueous extract in 15-liter plastic containers for 96 hours, during which period observations were made. Hatching success and water quality variables were determined according to standard procedures. The study revealed significant alterations in physico-chemical parameters, including dissolved oxygen (3.27 mg/l), pH (4.07), conductivity (63.11uS/cm), total dissolved solids (32.1 mg/l), and biochemical oxygen demand (0.67 mg/l) across treatment groups. A dose-dependent effect of T. tetraptera on hatching success was observed, with higher concentrations (T1 and T2) leading to decreased hatching rates. The T6 group exhibited the highest hatching success of 90%, while other treatment groups showed significantly (p<0.05) lower rates, with the highest concentration (75ml/l) resulting in only 10% hatching success. The findings of the present study underscore the potential risks associated with the use of T. tetraptera in capture fisheries. It also highlighted the need for strategic management of plant extracts to ensure the health and viability of fish populations and aquatic ecosystems.