fa aquaculture aquaculture پژوهشي Orginal research papers In the present study effects of different levels of probiotic <em>Pediococcus acidilactici</em>, on growth performance and survival rate of <em>Rutilus kutum </em>fingerlings were investigated. Kutum fingerlings with a mean weight of 1&plusmn;0.235&nbsp;g were reared for 8 weeks in 500-l fiberglass tanks (15 fish per tank) with 4 diet treatments (3 replicates for each). Treatments included 1&times;10⁹, 2<span dir="RTL">:</span>1&times;10⁹, 3&times;10⁹ CFU kg^-1 dry food and a control without probiotic. At the end of the study, specific growth rate (SGR) and survival rate (SR) were significantly higher in treatments supplemented with probiotic compared to the control (<em>p</em><0.05), while the fish fed with probiotics showed lowest food conversion ratio (FCR) (<em>p</em><0.05). The results indicated that the use of 3&times; 10⁹ CFU kg^-1 dry food probiotics improved growth parameters and survival rate in <em>R. kutum </em>fingerlings. Rutilus kutum, Probiotic, Pediococcus acidilactici, Growth, Survival 35 46 http://jifro.ir/browse.php?a_code=A-10-1122-2&slc_lang=fa&sid=1 A.R. Valipour valipour40@gmail.com 100319475328460029671 100319475328460029671 Yes Inland Waters Aquaculture Research Center , Iranian Fisheries Science Research Institute (IFSRI), Agricultural Research Education and Extension Organization (AREEO), Bandar Anzali, Iran Inland Waters Aquaculture Research Center , Iranian Fisheries Science Research Institute (IFSRI), Agricultural Research Education and Extension Organization (AREEO), Bandar Anzali, Iran N. Hamedi Shahraki 100319475328460029672 100319475328460029672 No Science and Research Branch, Islamic Azad University, Rasht, Iran Science and Research Branch, Islamic Azad University, Rasht, Iran H. Abdollahpour biria 100319475328460029673 100319475328460029673 No Department of Fisheries, Talesh Branch, Islamic Azad University, Talesh, Iran Department of Fisheries, Talesh Branch, Islamic Azad University, Talesh, Iran