en Biology & physiology Biology & physiology پژوهشي Orginal research papers In this study growth characteristics of 815 tuwini (Capoeta trutta) in Shour River were investigated during July 2010 through June 2011. The population was composed of 62.94% females and 32.02% males. Sex ratio was 1: 1.96, with significant differences observed at 1:1 (x2= 150.6 df= 1 p<0.05). The age distribution of this population ranged from <1 to 6 years. The distribution of length and weight was between 95 and 300 mm. The average length, except in <1 year olds, was statistically significant between sexes and average weight in all age groups was statistically significant between sexes (p<0.05). Weight-length relationship was determined as W=0.0115L2.9475 (R=0.91) in males and W=0.0096L3.0025 (R= 0.88) in females. Von-Bertalanffy growth equation was Lt= 24.5(1-e -0.333(t+2.54)) for males and Lt= 36.4 (1- e -0.129(t+4.02)) for females. Growth performance index was also estimated as Φ=2.301 in males and Φ=2.223 in females. Capoeta trutta, Growth parameters, Shour river, Iran 262 274 http://jifro.ir/browse.php?a_code=A-10-1272-148&slc_lang=en&sid=1 M Taghavi Niya 100319475328460013263 100319475328460013263 No M Javaheri Baboli mehranjavaheri@gmail.com 100319475328460013264 100319475328460013264 Yes L Roomiani 100319475328460013265 100319475328460013265 No A Pazira 100319475328460013266 100319475328460013266 No F lakzaie 100319475328460013267 100319475328460013267 No