Assessment of Fluoride Bioaccumulation Potential in African Catfish (Clarias gariepinus) Reared in Fluoride Rich Water

Abstract

Fluoride bioaccumulation in fish poses a significant impact on their growth, survival and consequently to upper trophic levels. Few studies have reported the impacts of high fluoride concentrations and their accumulation potential to catfish in African settings. A 60-day catfish cultivation was conducted at Ngarenanyuki ward and the Nelson Mandela African Institution of Science and Technology (NM-AIST) in Arusha, Tanzania to determine fluoride bioaccumulation and its impacts to catfish growth and survival. Juvenile catfish were exposed to 36 mg F–/L pond water and synthetic water containing fluoride (NaF) concentrations of 5, 15, 36 and 45 mg/L in aquaria set at NM-AIST laboratory. Fluoride concentrations in fish tissues were analysed by ion- selective electrode. Fish survival rate was greater than 90% in ≤ 36 mg/L fluoride levels compared to 65.8% in 45 mg F–/L aquarium. Significant fluoride bioaccumulation was observed in fish bones (222.00 mg/kg, dry weight), gills (177.4 mg/kg), skin (9 mg/kg) and low amount in fillets (1.467 mg/kg). Fluoride bioaccumulation significantly rose with fluoride levels increase and exposure time (p = 0.000). The study concludes that high fluoride occurrence and its increased exposure time increases fluoride bioaccumulation in African catfish. Therefore, growing catfish in water containing ≥ 45 mg F–/L requires defluoridation process.