Reproductive biology of Catfish Chrysichthys auratus, Geoffroy Saint-Hilaire, 1809, (Family: Bagridae) from Damietta branch of the River Nile, Egypt

Reproductive biology of 803 specimens of Chrysichthys auratus from Damietta branch of the River Nile, Egypt was studied between January and December 2010. The overall sex ratio (M:F = 1:1.18) was significant at P < 0.05 and the ratio showed insignificant variation in summer and autumn. The length of the onset sexual maturity was 12.3 cm SL at age 1.34 years for males and 9.7 cm SL at age 0.56 years for females. C. auratus showed prolonged spawning season extending from October to June with a peak in March for both sexes and the fish restart their reproductive cycle in July. The maximum value for GSI and GI were shown in March for both sexes (GSI = 0.49% ± 0.30 and 11.17% ± 9.65 for males and females respectively and GI = 1.02% ± 0.64 for males and 22.85% ± 20.00 for females). The reproductive load was 0.464 and 0.366 for males and females respectively. The study of ova diameters showed protracted and indefinite spawning period with diameters ranging from 0.3 to 3.0 mm (mean value = 1.53 ± 0.45). The absolute fecundity ranged from 696 to 4687 eggs but the relative fecundity was from 70 to 247 eggs/unit fish length. The results showed that C. auratus has different life history strategies in Egyptian River Nile water than any other African Rivers.