ABSTRACT

The increasing reliance on plant-derived substances for fishing practices, particularly in tropical regions, raises significant concerns regarding their ecological impacts and toxicity to aquatic organisms. This study investigated the effects of two widely used ichthyotoxic plants Luffa cylindrica and Tetrapleura tetraptera on the embryonic development and hatching success ofthe Clarias gariepinus. The primary objective was to evaluate the acute toxicity ofthe plant extracts, their influence on water quality and associated oxidative stress levels in the fish embryos. To achieve the objective of this study, series of controlled hatchery and laboratory experiments were conducted over one year period at Michael Okpara University of Agriculture and Akwa Ibom State University. The experiments involved collection and preparation of mature fresh leaves from both plant species and determination of their bioactive constituents. Their aqueous extracts were subjected to bioassays to determine their lethal concentrations (LC50) and impacts on developmental stages ofthe fish. Physico-chemical parameters ofwater media used for the experiment, including temperature, pH, dissolved oxygen, ammonia, alkalinity, biological oxygen demand (BOD5), total dissolved solids (TDS) and total hardness were monitored throughout this period for 96- hours. Data was collected from laboratory analyses of water quality parameters, phytochemical screening, assessment of fish health through oxidative stress responses, embryogenesis and hatching success of the fish early stages, while data on haematological, histopathological, length-weight and body condition index evaluations were obtained in the grow out stage. Results revealed that both herbs impacted the physico-chemical characteristics of the water, with the highest concentration (70 ml/1) leading to decreased dissolved oxygen levels (3.01, 2.97 mg/1) and increased ammonia (0.04, 0.03 mg/1) concentrations for L. cylindrica and T. tetraptera, respectively. Acute toxicity tests indicated that!. cylindrica had a lower LC50 value (169.25 ml/1) compared to T. tetraptera (190.66 ml/1), suggesting a higher toxicity level, particularly at elevated concentrations. This study also reported that exposure to these plant extracts adversely impacted fertilization rate, hatching success and overall developmental stages ofthe fish. Hatching success was higher in control groups compared to those exposed to the extracts, with lower concentrations yielding better outcomes. Protective enzymes, superoxide dismutase (SOD) and glutathiones-transferase (GST) indicated a strong response to oxidative stress, with elevated SOD levels correlating with increased mortality rates. The study also revealed variations in haematological and histopathological characteristics of grow-out fish with length-weight relationslup showing negative allometry while body wellbeing remained poor. This study highlights the potential risks associated with the indiscriminate use of both plant extracts in capture fisheries, emphasizing the need for careful management of these herbicides to the'Sn,Seir adverse effects on the a9uatic ecosystems and fish. The study also underscores devehnmen1;? H UnderStanding to™ological impacts of plant extracts on fish health and for fXr d r.eC°"lmends a “ban on t