A PRELIMINARY HISTOLOGICAL STUDY ON OVARIUM DEVELOPMENT IN MIRROR CARP AND SCALED CARP (Cyprinus carpio L., 1758) INTRODUCED INTO GELINGÜLLÜ RESERVOIR, TURKEY

Carp (Cyprinus carpio) is the most common species of the Cyprinidae family and is among the important species commercially caught in the Gelingüllü Reservoir, Yozgat, Turkey. In this study, the reproductive biology of mirror carp and scaled carp in Gelingüllü Reservoir was studied in terms of the gonadosomatic index (GSI), fecundity, and ovarian histology. Ovaries were classified into 5 maturity stages based on histological data, as follows: 1. Chromatin-nucleolus stage (oocyte diameter is 20-60 µm); 2. Peri-nucleolar stage (oocyte diameter is 60-200 µm); 3. Cortical alveolar stage (oocyte diameter is 200-600 µm); 4. Vitellogenic stage (oocyte diameter is 600-1000 µm); 5. Maturation stage (oocyte diameter is 1000-1400 µm). When ovulation was completed, post-ovulatory follicles and atretic follicles were noted in the ovaries. The spawning period in both populations extended from April to July, but peak-spawning activity occurred in April and May. Absolute fecundity reached 2.133 million eggs in mirror carp and 1.628 million eggs in scaled carp. Ovaries that contained both yolk stage oocytes and postovulatory follicles indicated that carp is a multiple spawner. Histological analysis in the present study showed that female mirror carp and scaled carp had mature eggs that contributed to sustaining the both populations in Gelingüllü Reservoir