en عمومى General پژوهشي Research <strong>Background:</strong> The aim of this study was to assess the changes in plasma levels of antioxidant enzymes and melano-macrophage centers (MMCs) in immune tissues as biomarkers of yellowfin seabream (<em>Acanthopagrus latus</em>) exposed to phenanthrene (Phe) for 14 days.<br> <strong>Methods:</strong> The research was carried out at Khorramshahr University of Marine Science and Technology, Khorramshahr, Iran in Jan 2016. Thirty-six immature fish were intraperitoneally injected with coconut oil (10 &mu;l/g-bw) containing Phe (70mg/kg-bw) and compared with control group (without injection). Then tissue and blood samples were obtained at 1, 4, 7 and 14 d after injection.<br> <strong>Results:</strong> The SOD and CAT activity showed a significant decrease in fish exposed to Phe up to day 7, then activity increased at day 14 in Phe-treated fish (<em>P</em><0.05). The size and number of MMCs in treated fish in spleen and head kidney were higher than control.<br> <strong>Conclusion</strong><strong>:</strong> Changes in these parameters (SOD, CAT, and MMCs) might be used as useful biomarkers for <em>evaluating</em> <em>immunosuppressive</em> Phe in fish. Antioxidant Enzymes, Melano-Macrophage Centers, Phenanthrene, Yellowfin Seabream 43 47 http://ijt.arakmu.ac.ir/browse.php?a_code=A-10-446-2&slc_lang=en&sid=1 Mehrnaz Shirmohammadi shirmohammadim@yahoo.com 10031947532846006636 10031947532846006636 No Department of Marine Biology, Faculty of Marine Science, Khorramshahr University of Marine Science and Technology, Khorramshahr, Iran. Mohammad Taghi Ronagh 10031947532846006637 10031947532846006637 No Department of Marine Biology, Faculty of Marine Science, Khorramshahr University of Marine Science and Technology, Khorramshahr, Iran. Negin Salamat 10031947532846006638 10031947532846006638 No Department of Marine Biology, Faculty of Marine Science, Khorramshahr University of Marine Science and Technology, Khorramshahr, Iran. Abdolali Movahedinia 10031947532846006639 10031947532846006639 No Department of Marine Biology, Faculty of Marine Science, Khorramshahr University of Marine Science and Technology, Khorramshahr, Iran. Gholamreza Hamidian 10031947532846006640 10031947532846006640 No Department of Basic Sciences, Faculty of Veterinary Medicine, University of Tabriz, Tabriz, Iran.