Publication

Abstract : Oreochromis niloticus (Linnaeus 1758) (Nile tilapia), with a known ability to adjust to various environmental conditions, have high potential for aquaculture. For determination of population structure of alien fish species, O. niloticus, random samples were collected monthly from March 2008 to February 2009 in middle stretch of the Ganga river at Allahabad. This species is of great socioeconomic importance for the region and keeps active a population of about 600 to 700 fishers at Allahabad. The samples were measuring from 9.4 to 41.5 cm in length which varied from 0 to 5+ age groups. According to the percentage occurrence age group 2+ was dominant, male (26.11%) and female (27.47%), more than one fourth of the total population. Male population was dominated in 0 and 1+ age groups which shared 17.78% and 25.00%, respectively while female population was dominated in 2+, 3+, 4+ and 5+ age groups and shared 27.47%, 15.93%, 11.54% and 5.49%, respectively. In the stock, female population was slightly greater than male. The 5+ age group indicated that the ecological condition was favorable for O. niloticus in the middle stretch of the Ganga river. Approximately 90% of fishes were mature in the present samples. The present study indicates dominance of female population of O. niloticus in the Ganga river. It is believed that this healthy age composition of O. niloticus is due to habitat degradation and water quality of the river stretch.