en Stock assessment Stock assessment پژوهشي Orginal research papers Length-Based Spawning Potential Ratio (LB-SPR) model was applied to describe the status of Javelin grunter, <em>Pomadasys kaakan</em> in the Persian Gulf and Oman Sea. From April 2002 to March 2019. 45,489 specimens were collected from fish landing sites monthly, and their length (FL) and weight were measured. The results of the present study showed that different gears captured most of the <em>P. kaakan</em> before first spawning time. The maximum-recorded length for this species in the study area was 60 cm FL with a mean length of 43.0&plusmn;4.73 cm. The M/K value corresponds to <em>P. kaakan</em> maturation was calculated as 0.53. Based on the LB-SPR assessment model, it could be concluded that these species become vulnerable to fishing at its maturation&rsquo; size (48 cm). The range of annual SPR of <em>P. kaakan</em> was estimated between 0.14 to 0.18 in the Persian Gulf and Oman Sea (Iranian waters), which is even lower than the threshold value of 0.2<span dir="RTL">.</span> Such results suggest that the exploitation of <em>P. kaakan</em> occurred above the maximum sustainable limit and has a confounding effect on successful recruitment and juvenile survival of this species. The Spawning Potential Ratio of <em>P. kaakan </em>based on time series analysis, as a biological reference point was estimated below 0.2, which means for achieving a higher SPR level and sustainable fisheries, the rate of fishing mortality should be reduced constantly. Length frequency, Sustainability, Spawning Potential Ratio, Pomadasys kaakan, Persian Gulf, Oman Sea 1560 1572 http://jifro.ir/browse.php?a_code=A-10-86-5&slc_lang=en&sid=1 A. Vahabnezhad AVN9400@gmail.com 100319475328460042711 100319475328460042711 Yes Iranian Fisheries Science Research Institute (IFSRI), Agricultural Research Education and Extension Organization (AREEO), Tehran, Iran S.A. Hashemi seyedahmad91@gmail.com 100319475328460042712 100319475328460042712 No . Offshore Fisheries Research Center, Iranian Fisheries Science Research Institute, Agricultural Research, Education and Extension Organization (AREEO), Chabahar, Iran S.A. Taghavimotlagh s_taghavimotlaghhotmail.com 100319475328460042713 100319475328460042713 No Iranian Fisheries Science Research Institute (IFSRI), Agricultural Research Education and Extension Organization (AREEO), Tehran, Iran Gh. Daryanbard daryanabard@gmail.com 100319475328460042714 100319475328460042714 No Caspian Sea Ecology Research Center, Iranian Fisheries Science Research Institute, Agricultural Research Education and Extension Organization (AREEO), Sari, Iran