Assessment of fluoride bioaccumulation in catfish grown in fluoride rich waters

A Dissertation Submitted in Partial Fulfillment of the Requirements for the Degree of Master’s in Environmental Sciences and Engineering of the Nelson Mandela African Institution of Science and Technology, TanzaniaFluoride bioaccumulation in fish poses a significant impact to their growth performance, survival and consequently to the upper trophic levels. Few studies have reported the impact of high fluoride concentration and their accumulation to catfish in African settings. A 60-days African catfish (Claris gariepinus) cultivation was conducted at Ngarenanyuki ward and at the Nelson Mandela African Institution of Science and Technology (NM-AIST) laboratory in Arusha, Tanzania, to determine fluoride bioaccumulation and its effect on growth and survival of the catfish. The juvenile catfishes were exposed to water containing 36 mg Fˉ/L in a fishpond and synthetic water containing fluoride concentrations (NaF) of 5, 15, 36 and 45 mg/L in the aquaria set at NM-AIST laboratory. Fish growth and survival was determined and the fluoride concentrations in fish tissues were analysed by ion selective electrode. At the end of the experiment, fish survival rate was greater than 90% in fluoride levels of 5, 15, 36 mg/L compared to 65.8% in 45 mg/L aquaria treatment. Also, significant fluoride bioaccumulation was observed in fish bones (222.00 mg/kg, dry weight) followed by gills (177.4 mg/kg), skin (9 mg/kg) and low amount in fillets (1.467 mg/kg). In all these tissues, fluoride bioaccumulation significantly rose with increase in fluoride levels in the water and exposure time (p< 0.001). From this experiment, it is concluded that high fluoride occurrence in surface water led to increased bioaccumulation in the African catfish and correlates with exposure time. Therefore, to grow catfish in water containing more than 45 mg/L requires a deflouridation process to take place