Samples of Senilia senilis were collected in the Benya lagoon, (5°N, 1°23'W) Ghana, and were classified into two size classes based on the shell length (< 2.9cm and > 2.9cm) and analyzed for their mercury (total and organic) and organochlorine concentrations. The total mercury concentration varies between 0.03 and 0.64 µg/g dw (median = 0.2µg/g dw) and tends to decrease with size. The percentage average concentration of organic mercury was 49 ± 25% and ranges between 0 to 110% of the total mercury .This percentage has no relationship with size. Both total and organic mercury have no relationship with the condition index of the clams. However, there is a significant difference between the condition index of the larger clams and the smaller ones. PCB pattern found in the samples was different from that of the two standard mixtures Aroclor 1254 and 1260. As a result the concentrations were discussed on the basis of eight individual congeners (101-180). There was no difference between the two size classes in PCB concentrations either on lipid or dry weight basis. No relationship was found between condition index and PCB concentrations. The sum congeners ranges between 48-351 ng/g dry weight (median =102 ng/g dw) and 0.72 -5.4 µg/g lipid weight (median = 2.22 µg/glw) respectively. The correlation between lipid content and the PCB concentration shows a direct uptake of pollutant through adsorption, absorption and partitioning from the water to the lipid content. The DDT to DDE ratio in the results reflect the recent exposure to this residue.
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