en aquaculture aquaculture پژوهشي Orginal research papers <span lang="TR" style="font-size:11.5pt"><span calibri="" style="font-family:"><span style="color:black">This research investigated the effects of dietary cobalt chloride (CoCl₂) and ascorbic acid (AA) on growth, physiological, and molecular parameters in Siberian sturgeon (<i>Acipenser baerii</i>). Two hundred seventy juveniles were divided into eight groups fed diets containing 2 or 4 mg/kg CoCl₂ and 200 or 800 mg/kg AA for 12 weeks. Results showed significant differences in final weight, length, weight gain, and growth rate among treatments (<i>p</i><0.05), indicating differences when compared to the control group. However, no significant difference was observed in specific growth rate, condition factor, Average daily growth, or protein efficiency ratio compared to the control (<i>p</i>>0.05). The lowest and highest AA/cobalamin levels were found in the control and the 4 mg/kg CoCl₂ with 200 mg/kg AA, and the 2 mg/kg CoCl₂ groups, respectively (<i>p</i><0.05). Maximum serum iron level was observed in fish fed 800 mg/kg CoCl₂, and the lowest glucose was in the control (<i>p</i><0.05). The cortisol level was significantly higher in 2 mg/kg CoCl₂ with 200 mg/kg AA group compared to the control, which had the lowest levels (<i>p</i><0.05). The highest <i>hsp70</i> and <i>p450</i> gene upregulation, as well as the highest <i>GH</i> and <i>igf-1</i> expression, occurred in the 4 mg/kg CoCl₂ with 200 mg/kg AA group, with the lowest expression in the control (<i>p</i><0.05). Overall, 4 mg/kg CoCl₂ and 200 mg/kg AA supplementation had more positive effects on growth performance, hematological and biochemical indices, and the modulation of genes associated with growth, stress response, and immunity in Siberian sturgeon.</span></span></span> Micronutrients, Growth, Physiological indices, Gene expression, Acipenser baerii 1451 1476 http://jifro.ir/browse.php?a_code=A-10-4141-4&slc_lang=en&sid=1 S.M.S Roudbaraki sadegh.roudbaraki@gmail.com 100319475328460058199 100319475328460058199 No Fisheries Department, Lahijan Branch, Islamic Azad University, P.O. Box 1616, Lahijan, Iran H. Ershad Langroudi ershad5353@gmail.com 100319475328460058200 100319475328460058200 Yes Fisheries Department, Lahijan Branch, Islamic Azad UFisheries Department, Lahijan Branch, Islamic Azad University, P.O. Box 1616, Lahijan, Iranniversity, P.O. Box 1616, Lahijan, Iran A.A. Zamini novin.print@yahoo.com 100319475328460058201 100319475328460058201 No Fisheries Department, Lahijan Branch, Islamic Azad University, P.O. Box 1616, Lahijan, Iran B. Falahatkar falahatkar@guilan.ac.ir 100319475328460058202 100319475328460058202 No Fisheries Department, Faculty of Natural Resources, University of Guilan, Sowmeh Sara, P.O. Box 1144, Guilan, Iran R. Safari fisheriessafari@yahoo.com 100319475328460058203 100319475328460058203 No Fisheries Department, Faculty of Fisheries and Environment, University of Agricultural Sciences and Natural Resources, P.O. Box 4913815739, Gorgan, Golestan, Iran