Biology of Cirrhinus mrigala and Oreochromis niloticus

Present investigation was aimed to understand the biodiversity, landing scenario, age and growth, sex ratio, population structure and population dynamics of commercially important fishes Cirrhinus mrigala and Oreochromis niloticus. The fish samples were collected on regular basis during the period August 2011 to July 2012 from the lower stretch of the Yamuna river at Allahabad, India. Fish biodiversity of the Yamuna river at Allahabad consisted of 85 fish species belong to 8 orders, 28 families and 63 genera. Cypriniformes and Cyprinidae were the most rich species order and family. Data on fish landings showed that the O. niloticus and C. carpio have invaded in the lower stretch in a big way in the Yamuna river at Allahabad. The estimated annual catch was dominated by O. niloticus (147.81kg d-1) followed by C. carpio (132.04 kg d-1) and miscellaneous group (92.34 kg d-1) and they accounted for 24.36%, 21.76% and 15.22% in total, respectively. On the basis of samples of C. mrigala in the length range from 16.8 to 94.3 cm showed that the fish attained mean length of 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