Size Selectivity of Active Fishing Gear: Changes in Size, Age and Growth ofCirrhinus Mrigala from the Ganga River, India

摘要

Good knowledge of netting approach is essential for scientific and sustainable based fisheries management inlotic water bodies. The large sizes of fishes are more attract to fishers compared to small fishes. This type of fishingis very harmful for future stock and recruitment. 1.5 inch to 3.5 inch mesh size cast net was used in the Ganga Riverat Allahabad. Cirrhinus mrigala is mainly captured by drag net from the Ganga River, India. Studies were undertakenduring March 2014 to February 2015 from the middle stretch of the Ganga River, India. 423 fish specimens (206males and 217 females) were examined of Cirrhinus mrigala. An over-all picture of age, growth increment and agecomposition of C. mrigala has been obtained by the study of its scales. The age composition of C. mrigala variedfrom 0+ to 10+. On the basis of pooled sampled specimen in the total length ranges varied from 16.8 cm to 92.4 cmshowed that the fish attained the mean length 30.24 cm, 48.02 cm, 61.50 cm, 70.31, 77.63, 81.84 cm, 85.30 cm,88.57 cm, 90.15 cm, 91.8 cm in 1+, 2+, 3+, 4+, 5+, 6+, 7+, 8+, 9+ and 10+ age groups respectively. The growthincrements in C. mrigala was recorded as 30.24 cm, 17.78 cm, 13.48 cm, 8.81 cm, 7.32 cm, 4.21 cm, 3.46 cm, 3.27cm, 1.58 cm and 1.65 cm for 1+ to 10+ age groups, respectively. The maximum growth increment was recorded in1st year and minimum in 9th year of life. The slow growth increment observed after third year may be attributed tothe maturity attained after second year of life. It is well known that the growth potential is used for the gonaddevelopment. Drag netting is reducing the size of C. mrigala in the Ganga River.