en aquaculture aquaculture پژوهشي Orginal research papers A two-month feeding trial was conducted to evaluate the effect of partial replacement of fish meal (FM) by soybean protein (SP) alone or in combination with lysine (Lys) and methionine (Met) supplementation in practical diets for silvery-black porgy juveniles (16.7&plusmn;0.1 g). Seven isoproteic (<em>ca.</em> 50% crude protein) and isoenergetic (<em>ca. </em>22.4 MJ kg^-1) diets were formulated in which 45% (SP45), 60% (SP60) and 75% (SP75) of FM protein were replaced by SP and the control diet (FM) was prepared with FM as the major source of protein. In SP45⁺, SP60⁺ and SP75⁺diets, 45 to 75% of FM was replaced by SP with supplementing blends of Lys and Met. Growth performance, feed utilization, and protein and lipid digestibility decreased with increasing dietary SP levels (<em>p</em><0.05). Fish fed SP75 had the highest whole body lipid content, but with the lowest whole body arginine, lysine, histidine, phenylalanine and taurine concentrations (<em>p</em><0.05). Supplementing Lys and Met in SP based diets did not improve growth performance, suggesting that the anti-nutritional factors in soybean protein products rather than Met and Lys deficiency might limit FM substitution with SP in silvery-black porgy juveniles.<br> &nbsp; Fishmeal replacement, Lysine, Methionine, Growth performance, Body composition, Sparidentex hasta 1329 1343 http://jifro.ir/browse.php?a_code=A-10-2220-1&slc_lang=en&sid=1 M. Yaghoubi m.yaghoubi@ut.ac.ir 100319475328460034823 100319475328460034823 Yes Iranian Fisheries Science Research Institute, Agricultural Research Education and Extension Organzation (AREEO), Ahwaz, IRAN. M. Torfi mozanzadeh mansour.torfi@gmail.com 100319475328460034824 100319475328460034824 No Iranian Fisheries Science Research Institute, Agricultural Research Education and Extension Organzation (AREEO), Ahwaz, IRAN. J. Ghafle Marammazi jmarammazi06@gmail.com 100319475328460034825 100319475328460034825 No Iranian Fisheries Science Research Institute, Agricultural Research Education and Extension Organzation (AREEO), Ahwaz, IRAN. O. Safari omidsafari@um.ac.ir 100319475328460034826 100319475328460034826 No Department of Fisheries, Faculty of Natural Resources and Environment, Ferdowsi University of Mashhad, Khorasan Razavi, Iran F. Hekmatpour hekmatpourf@gmail.com 100319475328460034827 100319475328460034827 No Iranian Fisheries Science Research Institute, Agricultural Research Education and Extension Organzation (AREEO), Ahwaz, IRAN. E. Gisbert Enric.Gisbert@irta.cat 100319475328460034828 100319475328460034828 No IRTA, Centre de Sant Carles de la Rápita (IRTA-SCR), Unitat de Cultius Experimentals, Crta. del Poble Nou Km 5.5, Sant Carles de la Rápita, Spain