The growth and mortality of Roach (Rutilus rutilus caspicus ,Yakovlev,1870) in the southern waters of the Caspian Sea (Golestan province)

In this study, the biological characteristics and dynamics of the fish population of Roach (Rutilus rutilus Caspicus, Yakovlev,1870 (in coastal waters of Golestan province has been studied. 384 specimens of fish were collected from coastal waters of Golestan province by gillnet and beech sin from April 2015 to March 2016. The smallest and largest lengths fish that were caught at14 and 26 centimeters, and the minimum and maximum weights were 28 and 246 gr. The rate of b for male and female was 3.012 and 3.205 respectively. To determine the growth parameters, we used the age determination from scales. And frequency distribution of length, (Fonbrtal- growth factors) was found in male and for female. W∞ was estimated about 216.466 gr in males and 259.77 in females. The natural and fishing mortality rates in both males and females were 1.13, 0.401 and 0.84, 0.673 per year. Also, in the present study the utilization factor was Φ'= 0.26 and Φ'= 0.43 in males and females. The growth performance index in Golestan province was estimated about 2.57 for males and 2.48 for females. The age group was from one to four years old. , the most frequent was at one to positive two years old.