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Among the several fish species commercially exploited at the Persian Gulf and Oman Sea waters, the Largehead hairtail, Trichiurus lepturus, stands as one of the most influential groups that have been recently exploited for export to outside markets. In the current study, we applied the Beverton and Holt's relative yield per recruit model to provide management guidance and determine the biological reference points (i.e. E_0.5 and E_max) for T. lepturus stock in the coastal waters of Iran. The von Bertalanffy growth equation (VBGF) was fitted to length–frequency data (n =1309) to obtain a VBGF with the following parameters: L_∞=111.3 cm total length; K=0.41 and t₀= -0.28 years. The estimated value of total mortality (Z) based on length converted catch curve method was 1.11 year^-1. Natural mortality (M) based on growth parameters was 0.67 year^-1 while fishing mortality (F) was recorded as 0.44 year^-1. Maximum exploitation rate (E_max), corresponding to the maximum relative yield per recruit was E_max = 0.62. The stock was not overexploited, since E < E_max. The present results have to be considered with caution to fisheries management purposes as fishing effort is still in increasing phase. The long-term monitoring is required to better understand the T. lepturus population dynamic and its fishery framework in the study region.
 

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Golden grey mullet (Chelon auratus) is one of the most important commercial species of the Caspian Sea. Considering its economic importance, some characteristics population dynamics indices  catching status were studied in south-east of Caspian Sea (Golestan coasts). In this study, 886 speciements were collected and became biometrics during the period of 2014-2015.  Speciemens were range fork length 20-52 cm and 125-1235 g and most frequency (11.2%) belong to 29-30 cm groups. Infinity length (L∞) and growth coefficient (k) were estimated 54.08 cm and 0.34 year^-1, repectively. The relationship between length and weight, the value of b was 2.8368, indicating a negative allometric growth model. Total mortality, natural, fishing and exploration rates were calculated 1.13, 0.58, 0.55, and 0.49 year ^-1, respectively. Its biomass and maximum sustainable of yield  (MSY) were estimated 994749 kg and 305824 kg, respectively in 2016, while catch ration was 330770 kg in Golestan coasts. Thus it was 8% overfishing from permitted limit. Overall, regardness the maximum allowable catch is essential for sustainable management and conservation of stocks.