This study was undertaken in two separate environmental and experimental conditions. The environmental test was carried out at creeks in the Persian Gulf and the experimental test was undertaken in seawater re-circulatory tanks. Mercury concentrations were determined using a standard cold vapour atomic absorption method. Serum enzymes were determined with Diagnostics Infinity reagent kit. Serum glucose and total protein were measured photometrically. Serum hormones were assayed using diagnostic ELISA kits. Results of the present investigation indicated that the sub-acute and chronic mercury concentrations tested may cause several changes in the biochemical and hormone parameters of the studied fish and we can use these changes as biomarkers for mercury detection. The range of mercury concentrations found in the creek water and specially sediments along the Mahshahr coast was higher than the other marine environment. It was declared that between enzymatic indices serum acid phosphatase (ACP) amount and ACP activity, between hormonal indices testosterone, T3 and T3/T4 and between metabolite index total protein can be considered as suitable and effective biomarkers of mercury pollution in yellowfin seabream.