Age, growth and reproduction of Chondrostoma regium (Heckel, 1843) from the Zayandeh Roud River, Iran

Age, growth and reproduction were investigated for Chondrostoma regium, collected monthly (November 2007- August 2008) from the Dimeh Spring region, Zayandeh Roud River, Iran. The maximum age of collected female and male fish were estimated based on scale increments as five and four years respectively. Von Bertalanffy growth equations were calculated as L_t=246[1-e^(-0.206(t-0.034))], W_t=163.29〖[1-e^(-0.206(t-0.034))]〗^2.77 for females and L_t=253.1[1-e^(-0.206(t-0.175))], W_t=188.25〖[1-e^(-0.206(t-0.175))]〗^2.99 for males. Size ranges of the male and female specimens were almost similar. The fork length range for females was 10.5-18.0 cm and 10.7-19.7 cm for males and the weight range was 15.7-85.4 g in females, and 14.5-88.5 g in males. The female-male ratio was 1.8:1 (p<0.05), and for both sexes gonadal development and sexual maturity occurred in the second year of their life. Length-weight relationships revealed isometric growth pattern for males and a negative allometric growth for females. Monthly data of Gonadosomatic Index, and ovary condition suggested that spawning occurred during May and June. The mean absolute and relative fecundity was calculated as 2429±1512 (eggs/female) and 78.118.7 (egg/g), respectively, and fecundity was significantly correlated with both body weight (r2=0.90) and fork length and (r2=0.84).