Growth pattern, condition factor and heavy metal concentration in Blackchin Tilapia, Sarotherodon melanotheron from Lagos Lagoon

Abstract

The growth pattern, condition factor and heavy metals concentrations in tissues of Sarotherodon melanotheron from Lagos Lagoon were investigated from April to July 2013. The Lagos Lagoon has been under intensified pollution, which affects fish and poses a public health risk. The size of the 55 specimens of S. melanotheron used ranged from 9.5-14.7 cm standard length (13.1-19.8 cm total length) and between 43.00 – 152.51 g total weight. The growth pattern reflected negative allometric growth. Mean monthly condition factor (K) values ranged from 4.28 to 4.67. Concentrations of heavy metals were higher in the rainy season than the dry season, except for Iron (Fe) which was higher in the dry season than the rainy season. In the present study, all the heavy metals: Ni (0.103±0.027 - 0.353±0.092); Cr (0.083±0.022 - 0.203±0.053) except Iron (25.100±6.572 - 77.797±20.372) and Mercury (0.020±0.006 - 0.060±0.016) were higher than the World Health Organization (2008) recommended permissible values in mg/kg: Pb (0.01), Cd (0.03), Ni (0.07); Cr (0.05); Fe (300) and Hg (0.5). Conclusively, the Lagos Lagoon is contaminated with Pb, Cd, Cr and Ni; periodic monitoring and control of effluent discharge into the lagoon is advocated to ensure safety of public health from fish consumption.

Keywords: Growth types, bone, egg, flesh, trace metals, bioaccumulation, S. melanotheron