Intrabasin variation in growth models Capoeta capoeta (Guldenstaedt, 1773) in 5 streams of Gorganroud River basin

This study surveyed Intrabasin variation in the growth models of C. capoeta in 5 streams of Gorganroud River basin during the reproduction season between April and May, 2010 and 2011. A total number of 1500 specimens were caught through electro-shocking. Total length, total weight, sex and b-value were determined. Total length ranged between 4.1 and 20 cm and total weight ranged between 0.81 and 108.34 g in Pishkamer and Tilabad streams, respectively. The growth models were estimated separately for each sex. The b-value ranged from 2.90 for the males of Pishkamer and Tilabad to 3.13 for the females of Chelchai. Growth model was positive allometric (b>3) for most of the females, while the males had different growth models. A comparison between the b-value of the streams can aid the identification of the factors contributing to the growth model of the populations. In fact, different types of habitats differ in their general environmental conditions which can cause reactions. This reflects a change in the body form with population. This variation in the allometry coefficient of C. capoeta suggests different growth strategies for the populations.