CONCENTRATIONS OF POTENTIAL TOXIC METALS IN DIFFERENT AQUATIC FISH PARTS HARVESTED FROM TWO LAGOONS IN LAGOS NIGERIA
The level of some potential toxic metals (PTM) (Pb Ni Fe, Cu and Zn) in Synodontis membrane (Catfish), Tilapia zilli (Tilapia), from Lagos Island and Ikorodu (Ibeshe) lagoon were investigated using Atomic Absorption Spectrophotometer (AAS), model Buick Scientific 210 GVP, the analysis on all the samples were done in triplicates. The analysis of trace metals in Synodontis membrane and Tilapia zillii was conducted on head, trunk, intestine and gills the results showed the accumulation of metals occurred differently in various parts of the fish samples analysed. Lead (Pb) and nickel (Ni) were not detected (ND) in most of the samples except nickel that was found in the intestine of the sample in both lagoon. The absence of lead and sample may be attributed the existence of few or no industrial activities around the locations. The orders of accumulation in Tilapia were Gill>intestine >Trunk >Head and the pattern of distribution is Fe> Zn>Cu in all the organs from both lagoon.
In Catfish, the accumulation follows the order; Gills >Intestine>Head>Trunk respectively. The pattern of distribution of potential toxic metal in the catfish were Fe> Zn>Cu in all the organs of the sample analyzed. The mean values of the Catfish obtained fell in the ranges: Fe (39.93±0.72- 285.58±4.18); Cu (0.96±0.11- 5.84±0.37); Zn (26.00±0.41- 208.50±2.35) for Lagos Island and Ikorodu Lagoon respectively. The high concentrations of iron, zinc and copper were recorded in the sediment sample be a major depository of potential toxic metal and this may account for high concentration of the metals in the fish parts due to the fact that these metals are naturally abundant in Nigeria soils and since the source of metal depositories are the aquatic systems. The general drift of accumulations in all the organisms was Tilapia zillii>Chrysichthys nigrodigitatus. The analysis of the fish sample shows that concentrations of Fe, Cu and Zn in the samples are lower than the permissible limits set by WHO,USEPA and FEPA which indicate that the fish are safe for consumption therefore it is pertinent to regularly monitor the activities on both lagoons.
Keyword: Accumulation, human consumption, fish part, deposition, aquatic organisms