Toxic Effects of Raffia Palm (Raphia hookeri) Fruit Mesocarp on Oreochromis niloticus in Epebu Creek, Bayelsa State, Nigeria

Abstract

This study investigated the toxic effects of Raphia hookeri fruit mesocarp on Oreochromis niloticus over six months, from June to November 2022. Palm fruits and fish samples were collected from Epebu (Ogbomama) Creek and transported to the laboratory. The fish used included juveniles (2-4 cm, approximately 5 g) and adults (8-10 cm, averaging 90 g). Four test tanks and one control tank were established for the experiment. R. hookeri fruits were peeled, and the mesocarp was sun-dried for 10 hours, with 20 g used for chemical analysis. The remaining dried mesocarp was powdered, with 80 g macerated in 400 ml hexane at room temperature for 24 hours. The mixture was filtered and the hexane extract was concentrated using a rotary evaporator at 40°C. The extracted oil was stored at 4°C for further analysis, while the solid fraction was dried at 50°C for proximate composition analysis. The toxicity of the extract was tested on O. niloticus at a concentration of 5 g/l over 48 hours. The analysis of dead fish revealed proximate composition: water (61.15±0.10%), ash (1.02±0.02%), crude fibre (7.20±0.15%), crude protein (2.72±0.04%), fats (17.02±0.11%), and carbohydrates (10.89±0.34%). Mortality rates increased with concentration: 10 mg/l resulted in 1.33±0.33 and 2.00±0.00 mortality after 24 and 48 hours, respectively; 20 mg/l led to 5.67±0.33 and 7.67±0.33; and 40 mg/l caused 8.67±0.33 and 9.67±0.33. Alanine transferase (ALT) levels increased from 10.67±0.33 in the control to 26.33±0.88 at 40 mg/l. SOD and GPX levels were elevated in exposed groups, while GSH levels decreased with higher concentrations. The study concludes that R. hookeri fruit mesocarp is toxic to O. niloticus, affecting both juveniles and adults, and is not recommended for use in sustainable fish production. No known effects on humans were observed.