BIOCHEMICAL COMPOSITION OF OVARIES AND CHANGES IN BIOLOGICAL INDICES DURING OVARIAN MATURATION IN Schizothorax niger FROM DAL LAKE, KASHMIR

Histological and biochemical studies were conducted on the changes occurring in the ovaries of Schizothorax niger in Dal lake, Jammu and Kashmir from March 2018 to February 2019. This study was aimed to identify ovarian maturation stages histologically and to correlate them with their breeding period, organo-somatic indices and changes in the biochemical composition of the ovary. A total of 120 fish specimens taken were within the range of 24 cm to 43 cm in total length and weight ranging from 115 g to 510 g. Gonadal samples were taken and stained with Haematoxylin and Eosin and were studied under light microscope. Different stages of oocyte development were surveyed and thus, the oocytes identified included primary oocytes, cortical-alveoli oocytes, vitellogenic oocytes, mature oocytes and atretic oocytes. On the basis of presence of different oocytes, five different types of maturity phases were observed which include: Immature, maturing, mature, ripe and spent. During the experimental period, the mean gonadosomatic and hepatosomatic indices in fish exhibited remarkable variation throughout different maturity phases. Maximum gonadosomatic index (15.50 ± 0.75%) and minimum hepatosomatic index (1.87 ± 0.05%) were observed in the month of March indicating peak spawning period for Schizothorax niger. A significant inverse relationship between GSI and HSI was recorded. The single peak in gonadosomatic index during spawning phase (March) reflected that the fish is a spring spawner and an annual breeder. Ovarian biochemical study showed that the lipid (13.36 ± 0.18%) and protein (14.17 ± 0.24%) percentage were highest in spawning phase of ovary, while same were lowest in immature phase. Moisture was found highest (78.12 ± 0.64%) in immature phase and ash was found highest (2.41 ± 0.21%) in mature phase. The results revealed an inverse relationship between moisture and lipid irrespective of their maturity phases. It was concluded that by knowing the accurate breeding season and biochemical changes in ovaries with the progress of maturation we can protect this declining species in natural water bodies by artificial breeding and by formulating the nutrient-rich feed according to the requirement of ovaries at the appropriate phase of reproductive development.