en Stock assessment Stock assessment پژوهشي Orginal research papers <pre style="text-align:justify"> <span style="font-size:10pt"><span style="line-height:120%"><span style="font-family:Consolas"><span style="font-size:12.0pt"><span style="line-height:120%"><span new="" roman="" style="font-family:" times="">This study was conducted to determine the feeding and reproductive biology of&nbsp;<i>Saurida&nbsp;tumbil</i>&nbsp;and <i>Rastrelliger&nbsp;kanagurta</i>&nbsp;in the northern Oman Sea in 2020 -21. A total of 134 and 157 specimens of <i>S. tumbil</i> and <i>R. kanagurta</i> were collected from landing sites of Sistan and Baluchistan waters, respectively. The results of <i>S.&nbsp;tumbil</i>&nbsp;feeding analysis showed that the main diets of this species are fishes, mollusks and shrimps. Gastric emptying index (CV) indicated that this species was highly fed in winter and was identified as a gluttonous species. The results show the lowest value of&nbsp;Gonado-Somatic&nbsp;Index (GSI) in spring and the highest in summer.</span></span></span><span style="font-size:12.0pt"><span style="line-height:120%"><span new="" roman="" style="font-family:" times=""> T</span></span></span><span style="font-size:12.0pt"><span style="line-height:120%"><span new="" roman="" style="font-family:" times="">he reproduction of <i>S. tumbil</i> occurred after summer. Length (TL) at first maturity (LM50) for this species was estimated to be about 37.9 cm. The Food Preference (Fp) index showed that the main diets of <i>R.&nbsp;kanagurta</i> are phytoplankton and algae and CV reaches its maximum value in autumn. GSI of this species also shows the lowest level in spring and the highest in summer, which indicates that the peak of reproduction of <i>R.&nbsp;kanagurta</i>&nbsp;occurred after summer.</span></span></span><span style="font-size:12.0pt"><span style="line-height:120%"><span new="" roman="" style="font-family:" times=""> Length (TL) at first maturity (LM50) for this species estimated to be about 25.2 cm.</span></span></span><span style="font-size:12.0pt"><span style="line-height:120%"><span style="font-family:"Times New Roman",serif"></span></span></span></span></span></span></pre> Saurida tumbil, Rastrelliger kanagurta, Feeding habits, Reproductive habits, Northern Oman Sea 816 828 http://jifro.ir/browse.php?a_code=A-10-2470-3&slc_lang=en&sid=1 M. Doustdar mastooreh.doustdar@gmail.com 100319475328460046401 100319475328460046401 Yes Iranian Fisheries Science Research Institute, Agricultural Research, Education and Extension Organization (AREEO), Tehran, Iran. S.A. Hashemi seyedahmad91@gmail.com 100319475328460046402 100319475328460046402 No Offshore Fisheries Research Center, Iranian Fisheries Science Research Institute, Agricultural Research, Education and Extension Organization (AREEO), Chabahar, Iran. R. Rahmati 100319475328460046403 100319475328460046403 No Caspian Sea Ecology Research Center, Iranian Fisheries Science Research Institute, Agricultural Research, Education and Extension Organization, Sari, Iran.