age, growth and mortality of the persian sturgeon, acipenser persicus, in the iranian waters of the caspian sea

the age and growth of the persian sturgeon, acipenser persicus, obtained from the iranian coastal waters of the caspian sea, were studied through analysis of the pectoral fin ray section from 180 specimens, ranging in fork length (fl) from 66 to 203 cm. the specimens were obtained from commercial fisheries between october 2008 and june 2010. interpretation of growth bands in the pectoral fin ray sections was carried out objectively using the direct reading of thin sections and image analysis. the maximum age recorded in this study for the spacimens of persian sturgeon was 39 years. the von bertalanffy growth parameters estimated for females were greater than for males. the estimates of asymptotic length (l?) and growth coefficient (k) of females were 173.07 cm and 0.1 year -1, respectively and for males 164.33 cm l? and 0.08 year -1 k respectively,. total mortality coefficient (z) for females and males was estimated to be 0.45 and 0.76 year -1, respectively. this study revealed differences in life history parameters of the persian sturgeon compared with those of previous studies, which may be associated with the current increased fishing pressure and degradation of environmental conditions.