Environ Exp Biol (2016) 14: 69–73

The corollary effect of heavy metal accumulation in freshwater ponds on the hematological profile of Nile Tilapia (Oreochromis niloticus)

Abstract

The status of heavy metal buildup in commercial and non-commercial ponds of Nile tilapia (Oreochromis niloticus) and its effect on fish health was evaluated. Pond water and tilapia meat were examined for Pb, As, cadmium Cd and Cu using flame atomic absorption spectrometry; and Hg through manual cold-vapor atomic absorption spectrometry. Standard methods in hematology were applied to estimate red and white blood cell function of fish in relation to heavy metal accumulation. The results revealed significantly higher Cu content in pond water of a commercial farm compared to the Cu content of water from a non-commercial farm, while similar levels of Hg and Pb were recorded. Tilapia meat from commercial ponds had significantly higher Pb and lower levels of Cu compared to meat from a non-commercial farm. Similar levels of Hg were observed in tilapia meat obtained from farms while tilapia meat from non-commercial ponds had significantly higher Cu. Neither As nor Cd were detected in the farms. Hematological evaluation revealed comparable counts of total red blood cell. Red blood cell indices such as hematocrit and mean corpuscular volume were significantly higher in tilapia from the commercial ponds. The amount of hemoglobin per red blood cell was smilar in tilapia from the farms while mean corpuscular hemoglobin concentration was significantly higher in tilapia from the non-commercial farm. Total white blood cell and eosinophil counts of tilapia were similar in the farms. Tilapia from the commercial ponds had significantly high neutrophil and monocyte counts while tilapia from the non-commercial ponds had significantly high lymphocyte counts. The hematological evaluation indicate relationship of cellular components of fish blood and heavy metal accretion from the aquatic environment by Nile tilapia.