Toxicological effects of formaldehyde concentrations on African Cat fish, Clarias gariepinus fingerlings

Abstract

The acute toxicity of formaldehyde on African catfish (Clarias gariepinus) fingerlings was studied using the static bioassay. The fishes were fed twice daily at 2.5% of their body weight for 21 days. The rate of fingerlings mortality increased with increasing concentration of formaldehyde. The first death was noticed two minutes after the introduction of toxicant in the bowl with the lowest concentration in (30.0 mg/L), other behavioural symptoms include restlessness, rapid body movement, and difficulty in respiration displayed by fishes moving to the surface to gulp air, intense opercula movement, accumulation of mucus on body and loss of equilibrium by swimming sideways. A log concentration probit regression analysis was significant (p<0.05) and yield a co-efficient of determination, r 2 = 0.637. The LC50 and 95% confidence limits to the concentration of formaldehyde was determined as 1.80 ± 0.25 ppm and LC50 interval of 0.706 – 2.094 ppm. The results showed the necessity to regulate the discharge of formaldehyde from domestic and industrial sources into aquatic systems, hence the need for caution on it uses even in fish harvesting.