Age-related changes in ovarian gross and histological characteristics during pubertal development in captive Catla catla (Hamilton, 1822) of age 18-29 months

Annual reproductive cycle of female Catla catla was investigated during the age of 18-29 months through gross and histological studies. Catla is a warm water gonochoristic summer spawner. Ovarian development is quite fast with the increase in the temperature (above 29 degree C) and photoperiod (above 13.50 H) in April. Peak GSI (13.00 plus minus 9.30 %) was observed in June concomitant with the maximum water temperature and photoperiod. On the basis of gross and histological studies, seven ovarian stages namely, immature/resting, regenerating, developing, maturing, mature/ gravid, regressing and regressed were distinguished. Based on GSI studies, spawning seem to last for a very short period (mid June-mid July). Histological studies revealed six stages of oocyte development namely, chromatin nucleolar, perinucleolar, cortical alveolar, early vitellogenic, late vitellogenic and early germinal vesicle movement. Final cue for spawning seems to be the heavy monsoon rains. However, spawning in captivity was not observed in the present study as no final oocytes maturation or post-ovulatory follicles were seen. Total fecundity was measured in May and June separately. Relative fecundity was noted as 2537.80 plus minus 857.21 oocytes/g of ovary amounting to 41.33 plus minus 8.66 oocytes/g body weight in May of fish with 1861.40 plus minus 138.70 g body weight and 49.83 plus minus 2.05 cm total length. These values for the June fish were 1183.61 plus minus 681.72/g ovary and 121.73 plus minus 81.49/g body weight for fish of 1935.00 plus minus 225.70 gram average body weight and 49.67 plus minus 1.69 cm total length. Atretic follicles were quite prevalent in regressing ovaries. Since this is the first endeavor from Pakistan, results are discussed in the light of available literature and in comparison with the published work on this species elsewhere.