Study on some biological parameters of the Bitterling (Rhodeus amarus) in Sefidrood River (Guilan Province) and Siyahrood River (Mazandaran Province)

This study aimed to determine and comparison of age composition, sex ratio, growth model, and fecundity of the populations of Rhodeus amarus in Sefidrood River and Siyahrood River. In total 423 fish were caught monthly from February to June 2013. In Sefidrood River, were abundant males (58.2%) than females (41.8%) and in Siyahrood River, females (59.4%) than males (40.6%) and it was different from standard ratio (1male:1female). The fishes in Siyahrood River have had 1 till 8 years old and in Sefidrood River 1 till 9. The average of total length and body weight was 47.9±10.4 mm and 1.98±1.4g in Siyahrood River and 56.3±7.3 mm and 2.88±1.0 g in Sefidrood River, respectively and there were significant statistical differences between these parameters in both rivers(p