en Aquaculture and Health management Aquaculture and Health management پژوهشي Original research papers <p style="text-align: justify;">The present study tried to investigate the effects of <em>probiotic</em>, <em>Pediococcus acidilactici </em>in concentrations of 1&times; 10⁹, 2&times; 10⁹ and 3&times;10⁹cfu kg^-1 diet on growth and survival rate of oriental bream fry (<em>Abramis brama orientalis, </em>Berg 1949) in comparison to control diet (devoid of probiotic) for 60 days. In so doing, 180 specimens of oriental bream with initial weight of 2.69&plusmn; 0.22 g were divided randomly into12 fiberglass tanks (capacity 110 l).They were fed at 3-5 percent body weight daily. A the end of the trial, growth and survival rates were measured. &nbsp;The best growth performance was viewed in treatments rather than the control because of the improvement of gut microflora balance, which performed by probiotic <em>P. acidilactici</em>, following by the enzyme secretion for increasing nutrient digestibility and fish appetite. The best bodyweight gain, specific and daily growth rates, and&nbsp; the lowest feed conversion ratio was observed in treatment, feeding with diet containing 2&times; 10⁹cfu kg^-1 diet (P<0.05). The results of the current study revealed that it is the role of probiotic, <em>P. acidilactici </em>to the diet of oriental breamfry and <em>A. brama orientalis,</em> which resulted in growth performance increase and feed efficiency ratio improvement.&nbsp;</p> Probiotic, Pediococcus acidilactici, Growth, Feeding, Survival rate, Abramis brama orientalis 55 66 http://ijaah.ir/browse.php?a_code=A-10-35-38&slc_lang=en&sid=1 S Asadi Khomami 10031947532846001429 10031947532846001429 Yes Young Researchers and Elites Club , North Tehran Branch, Islamic Azad University, Tehran, Iran N Mooraki 10031947532846001430 10031947532846001430 No Faculty of Fisheries, Islamic Azad University, North Tehran Branch, Tehran, Iran A Valipour 10031947532846001431 10031947532846001431 No Aquaculture Institute of Inland Waters, Bandar Anzali, Guilan, Iran S Kakoolaki 10031947532846001432 10031947532846001432 No Aquatic animal Health and Diseases Department, Iranian Fisheries Science Research Institute (IFSRI), Agricultural Research, Education and Extension Organization (AREEO), Tehran, Iran