Growth parameters, mortality rates, yield per recruit, biomass, and MSY of Rutilus frisii kutum, using length frequency analysis in the Southern parts of the Caspian Sea

The growth and mortality coefficient of Rutilus frisii kutum, were estimated using length frequency data collected in southern waters of the Caspian Sea during October 2008 to April 2009. The following population parameters were evaluated: length-weight relationship, W = 0.004L 3.258, (r= 0.976); Von Bertalanffy growth constants, W? (g) = 4192.3, 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. 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 YPRmax = 287.535, 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.