The effects of bioaccumulation of heavy metals on fish fin over two years

Abstract

Nwabunike MO

The objectives of the study were to analyze the overall effects of bioaccumulation of heavy metals in fish tissue (fin) of (Clarias albopunctatus) over two years (2011 - 2013), and to propose recommendations for the general improvement of fish management in the study area. Multimesh gillnets were used to monitor the abundance and structure of the fish fauna. Stratified random sampling was carried out in each water body. The fishes were caught, identified, counted, graded, measured and weighed according to species. The species for chemical and histological analysis were taken immediately after weighing to the laboratory. Concentration of metals were studied in fish analyzing the tissue between the lateral lines and the fins, since high concentrations of metals do not imply that the metal have a toxic effect. It was observed that Fish fin had reduced bioaccumulation of cadmium. This ranged in the running effluent areas in 2011/2012 from 0.8 – 1.4 and 0.6 – 1.02 ppm in 2012/2013 with the two controls ranging between 0.2 – 0.4 ppm. Also, Nickel bioaccumulation in catfish fin had an ascending bioaccumulation during the two years with the range of 6.0 – 9.8 and control 1 has 3.1 – 4.2. Control 2 ranged from 1.0 – 1.5, showing that fishes in pond water had little or no nickel bioaccumulation. It was further observed that Mercury bioaccumulation in fish fin ranged from 0.4 – 0.6ppm and 0.7 – 1.2ppm in Akpara Dam and Enyigba fishes respectively. Enyigba ranged 0.8 -1.2ppm which was the highest. Ebonyi River ranged between 0.03 – 0.08 which was control 1 and pond water which was control 2 had no record of bioaccumulation. Again, Chromium had bioaccumulation in fish which ranged from 15-20 ppm in Akpara and Ebonyi River and had Enyigba fish fin at the ranges of 23 – 29 ppm with the Ebonyi River fish fin having 9 – 11ppm bioaccumulation and pond water having no record of bioaccumulation in its fish fin. Subsequently, the variation of lead and its bioaccumulation in the three running sites ranged from 0.5 – 1.3ppm. The control which was Ebonyi River had a range of 0.2 – 0.4ppm. The pond water had no bioaccumulation in its fish fin. Hence, bioaccumulation in fish fin increases with increasing age. The research also showed that Arsenic had a bioaccumulation range of 0.5 – 0.7 – 0.8 – 1.1ppm in the three running sites but with the first control which was Ebonyi River fish fin registering 0.2 – 0.5ppm in 2011 and 0.4 – 0.5ppm in 2012 in the second control having no bioaccumulation or less than 0.1 arsenic concentration. Based on the findings of this study, the following recommendations were made: There should be periodic monitoring of the heavy metals concentration in both the fishes and river system to ensure continuous safety of people in the area. Safe disposal of domestic wastes and control of industrial effluents should be practical and where possible recycled to avoid these metals and other contaminants from going into the environment. There should be further studies on the concentration of heavy metals in other fish tissues (brain, liver, kidney, intestine, and heart) and species. Neutralization of effluent water is recommended as a modern treatment practice such as lime precipitation of effluent water.