Juvenile Epinephelus coioides were exposed to three nominal concentrations (8, 32, 128 mg wet sediments L−1) of suspended sediments (SS) from Port Shelter (PS), Mirs Bay (MB) and Victoria Harbour (VH) for 10 and 30 days using semi-static system. Sediments from VH contained higher concentrations of Cu and polycyclic aromatic hydrocarbons (PAHs) than sediments from PS and MB. Gill damages including lamellar blood sinus dilation and vascular congestion were prevalent after just 10 days of exposure to SS. Fish exposed to SS at the highest concentration of 128 mg L−1 showed higher incidence of lamellar aneurism. Hyperplasia in the base of lamellae was recorded in fish that had been exposed to contaminated SS from VH. Significant increases in the density of chloride cells and mucous cells were found on the gills of fish that had been exposed to 128 mg L−1 of SS from PS. Clogging of gills by SS produced hypoxic-like responses in fish. Polluted sediments from VH produced addictive or synergistic effects between SS and chemical contaminants on fish.