Studies on age, growth and age composition of commercially important fish species, Cirrhinus mrigala (Hamilton, 1822) from the tributary of the Ganga river, India

Studies were undertaken during the period August 2011 to July 2012 from the lower stretch of the Yamuna river at Allahabad, India. During the present work, 565 fish specimens (274 males and 291 females) were examined for estimation of age, growth increment and age composition of C. mrigala. An over-all picture of age, growth increment and age composition of C. mrigala has been obtained by the study of its scales. The age composition of C. mrigala varied from 0+ to 10+ age group. On the basis of pooled sampled specimen in the length range from 16.8 to 94.3 cm showed that the fish attained the mean length 30.24 cm in 1+, 47.82 cm in 2+, 60.13 cm in 3+, 70.11 cm in 4+, 77.01 cm in 5+, 81.42 cm in 6+, 86.30 cm in 7+, 89.80 cm in 8+, 91.70 cm in 9+ and 94.30 cm in 10+ age groups. The growth increments in C. mrigala was recorded as 30.24 cm, 17.58 cm, 12.31 cm, 9.98 cm, 6.90 cm, 4.41 cm, 4.88 cm, 3.50 cm, 1.90 cm and 2.60 cm for 1+ to 10+ age groups, respectively. The maximum growth increment was recorded in 1st year and moderate in the subsequent years. The minimum growth increment was recorded in 9th year of the life. The slow growth increment observed after second year may be attributed to the maturity attained after second year of life. It is well known that the growth potential is used for the gonad development. The growth percentage varied from age to age in the pooled samples