en Stock assessment Stock assessment پژوهشي Orginal research papers <p style="TEXT-ALIGN: justify LINE-HEIGHT: 120% MARGIN: 0cm 0cm 0pt" class="Default"><a name="OLE_LINK12"></a><a name="OLE_LINK11"><span style="mso-bookmark: OLE_LINK12"><font size="3"><font face="Times New Roman"><span style="mso-fareast-font-family: 'Times New Roman'">The growth and </span>mortality coefficient</font></font></span></a><font face="Times New Roman"><font size="3"><span style="mso-bookmark: OLE_LINK11"><span style="mso-bookmark: OLE_LINK12"><span style="mso-fareast-font-family: 'Times New Roman'"> of </span><i>Rutilus frisii kutum</i></span></span><span style="mso-bookmark: OLE_LINK11"><span style="mso-bookmark: OLE_LINK12"><span style="mso-fareast-font-family: 'Times New Roman'">, were estimated using length frequency data </span></span></span><span style="mso-bookmark: OLE_LINK11"><span style="mso-bookmark: OLE_LINK12"><span style="COLOR: windowtext mso-fareast-font-family: 'Times New Roman'">collected in </span></span></span></font><span style="mso-bookmark: OLE_LINK11"><span style="mso-bookmark: OLE_LINK12"><span class="mediumtext1"><span style="LINE-HEIGHT: 120% COLOR: windowtext FONT-SIZE: 13.5pt">southern waters of the Caspian Sea</span></span></span></span><span style="mso-bookmark: OLE_LINK11"><span style="mso-bookmark: OLE_LINK12"><span style="mso-fareast-font-family: 'Times New Roman'"><font size="3"> during </font></span></span></span><span style="mso-bookmark: OLE_LINK11"><span style="mso-bookmark: OLE_LINK12"><span class="mediumtext1"><span style="LINE-HEIGHT: 120% FONT-SIZE: 13.5pt">October 2008 to April 2009</span></span></span></span><font size="3"><span style="mso-bookmark: OLE_LINK11"><span style="mso-bookmark: OLE_LINK12"><span style="mso-fareast-font-family: 'Times New Roman'">. The following population parameters were evaluated: length-weight relationship, </span>W = 0.004L ^3.258, (r= 0.976)</span></span><span style="mso-bookmark: OLE_LINK11"><span style="mso-bookmark: OLE_LINK12"><span style="mso-fareast-font-family: 'Times New Roman'"> Von Bertalanffy growth constants, W_∞ (g) = </span>4192.3</span></span><span style="mso-bookmark: OLE_LINK11"><span style="mso-bookmark: OLE_LINK12"><span style="mso-fareast-font-family: 'Times New Roman'">, L_∞ (cm) = 70.45, K = 0.2, per year t₀ = −0.75 total mortality and its components, Z = 0.92, M = 0.36, F = 0.56 per year. </span>The exploitation rate (E) was estimated about 0.6. The current yield per- recruit was estimated to be 279.15 g, which was only 1.2% less than Maximum yield per recruitment that was estimated as YPR</span></span></font><span style="mso-bookmark: OLE_LINK11"><span style="mso-bookmark: OLE_LINK12"><span class="SubtitleChar">_{<span style="LINE-HEIGHT: 120% FONT-FAMILY: "Times New Roman","serif" FONT-SIZE: 11pt FONT-WEIGHT: normal mso-fareast-font-family: Calibri mso-bidi-font-size: 12.0pt mso-bidi-font-weight: bold">max</span>}</span></span></span><span style="mso-bookmark: OLE_LINK11"><span style="mso-bookmark: OLE_LINK12"><span class="SubtitleChar"><span style="LINE-HEIGHT: 120% FONT-FAMILY: "Times New Roman","serif" FONT-SIZE: 11pt FONT-WEIGHT: normal mso-fareast-font-family: Calibri mso-bidi-font-size: 12.0pt mso-bidi-font-weight: bold"> = 287.535,</span></span><font size="3"> </font><font size="2">it means if fishing mortality increases from 0.56 per year to 0.7 per year, the yield will raise by only 1.2%. The current YPR and maximum YPR, which were gained at fishing mortality of 0.7, showed that most kutum individuals are caught before reaching the length of maturity. Therefore, to get a maximum YPR, it is necessary to increase fishing effort, even higher than the optimum level. Keeping kutum fishing at the current level will permit harvest of the sustainable yield and avoid overfishing problems.</font></span></span></font></p> Biomass, Caspian Sea, mortality, Rutilus frisii kutum, Exploitation rate 48 62 http://jifro.ir/browse.php?a_code=A-10-1-137&slc_lang=en&sid=1 P. Gheshlaghi p.gheshlaghi@gmail.com 10031947532846002673 10031947532846002673 Yes A. Vahabnezhad 10031947532846002674 10031947532846002674 No S. A. Taghavi Motlagh 10031947532846002675 10031947532846002675 No