The Loach, Oxynoemacheilus bergianus is native to Iran and there is little information about this species. Some biological characteristics of the species were examined by monthly collection of 358 specimens from the Kordan River in Alborz Province using hand net and cast net during September 2013 to August 2014. The Total length range was 32.36-74.36 mm (50.95±10.3SD), and the total weight range was 0.31-4.06 g (1.12±0.68). The maximum age based on otolith readings was 4 + years for males and 5 + years for females. The most frequent age groups were 3 + and 2 + in females and males, respectively. The length-weight relation for females was W=0.0079TL 2.99 (r 2 =0.92) and for males was W=0.0093TL 2.84 (r 2 =0.92). The growth pattern for both sexes was negative allometric. The Von Bertalanffy growth model was estimated as Lt=94.3[1-e -0.15(t+2.5) ] and Lt=86.9 [1-e -0.16(t+3.1) ] for females and males, respectively. The growth performance index was estimated as 7.19 and 7.09 for females and males, respectively, indicating a faster growth rate for females. Based on macroscopic gonad observation, the age of mature was 2 + for females and 1 + for males. Sex ratio was 1Female:1.1Male, not significantly different from the expected ratio. Maturation cycle consisted of five stages. The Gonadosomatic Index (GSI) indicated that reproduction of the fish occurred between February and June, with the highest mean value in April and May for both females and males. Oocyte diameters ranged from 0.15 to 1.33 mm (0.44±0.2). Absolute fecundity ranged between 363 and 2595 (1133±671) eggs. Absolute fecundity and total length (r 2 =0.58) and total weight (r 2 =0.66) were relatively with a good correlation. The relative fecundity was 993 ± 286 (583±187). Therefore, Oxynoemacheilus bergianus is a species with a short lifetime, rapid growth in the first and second year of life and early sexual maturity. This species has a high fecundity and reproduce in a long period from February to June. Keywords: Growth, Reproduction, Nemacheilidae, Kordan River, Iran, Oxynoemacheilus bergianus.
