Age Related Seasonal Changes in the Gonadal Activity of the Fish Notopterus notopterus (Pallas)

Oogenetic and testicular activity of N. notopterus was studied in relation to age and different the seasons in a year. The age was determined based on the annuli on the scale (Scalimetry) per year. Age at first maturity was determined based on the gonadal changes in a seasonal cycle. One year age group of fish during March shows maturing ovary with tertiary nucleolus staged ova 2.3 % (2.0 0.21) and migratory nucleus staged ova 1.26 % (1.1 0.1) with highest number of oogenetic elements in total it is 86.9 2.53. In August it is 7. l % of (5.3 0.15) tertiary nucleolus stage and 2.13 % (1.6 0.16) of migratory nucleus. Similarly, in March the testis shows spermatids 26.13 % (117.8 1.1) and spermatozoa 25.86 % (31.5 0.32). In August it is 19.26 % (61.5 0.47) of spermatids and 25.86 % (117.7 0.42) of spermatozoa. This indicates that the fish attains first maturity in one year age of its life, with moderate gonadal activity. Histological structure of two year matured fish shows all nine stages of oogenetic and spermatogenic elements during spawning period. The ovary shows different stages of oogenetic elements (total 118.3 1.35) bearing 45.98 % of tertiary nucleolus staged ovum and 1.68 % of migratory nucleus ovum. The lobules of testis shows different stages of spermatogenic elements (total 1077.3 1.57) with abundant spermatozoa i. e. , 843.2 0.48 (78.26 %) in March and 728.4 0.16 (74.53 %) in August. Thus 2-year aged fish showing high degree of spermatogenesis. The degree of gonadal activity is 0 age