Investigation of reproductive biology of Capoeta gracilis (Keyserling, 1861) in Zav River Golestan of National Park

To study the biological characteristics of Capoeta gracilis with 171 fish samples that obtained in December 2015 to May 2016 Electroshocker devices.  Sex ratio of male to female was 1.67:1 that showed significant difference between sex ration of male to female in population (X2 = 6.211, p < 0.05).  Maximum total length and weight were 199 mm and 122.43 g for females, 191 mm 93.37 g for males. The weight - length relation of female was W = 0.0097 TL3.11 (r2 = 0.99) and the weight - length relation of male was W = 0.0142 TL2.94 (r2 = 0.99) and the total relation was W = 0.0124 TL3.00 (r2 = 0.99). The results showed positive allometric growth for female and  negative allometric growth for male and  Isometric growth for the population (t-test, tmale= 2.09, tfemale = 2.77, tpopulation= 0.09, p < 0.05). Average absolute fecundity was 17978.11, while relative fecundity (eggs/g) were 1434.06. Eggs diameters were ranged from 0.10 to 0.98 mm with a mean value of 0.44 mm. The highest mean Gonadosomatic for females and for males in April was observed in June, 4.75 and 7.51 for female and male respectively.