Age and growth of Alburnus mossulensis (Cyprinidae) in Bibi-Sayyedan River of Isfahan Province

Population structure and growth of Mossul bleak, Alburnus mossulensis, a native species of cyprinids in Bibi-Sayyedan River of Semirom, Isfahan, were investigated by monthly sampling during December ۲۰۱۰ to December ۲۰۱۱. For this purpose, ۵۴۳ speciments (۳۵۳ females, ۱۵۹ males and ۳۱ immature) were caught using seine net (۵ mm mesh size) and a cast net. Age groups of males and females were ۰+ to ۵+. The most frequent age group was ۲+ in both sexes. The sex ratio was ۱M:۲.۲F (p<۰.۰۱). Males outnumbered the females in younger age classes and females outnumbered the males in older age groups. The highest condition factor was observed in April for males and in March for females. The mean condition factor (CF) was not significantly different between the sexes among all fish during different months (p>۰.۰۵). The largest female was ۱۶.۸۰ cm in total length and ۴۹.۱۲ g in weight, while the largest male was ۱۴.۱۰ cm in total length and ۲۸.۱۹ g in body weight. The length-weight relationship was calculated as W = ۰.۰۱۶۹L۳.۰۳۵۵ (r۲=۰.۹۵) for males, W=۰.۰۰۶۱L ۳.۱۷۵۱ (r۲=۰.۹۸) for females and W=۰.۰۰۶۶L۳.۱۳۹ (r۲=۰.۹۹) for all fish (males, females and immature). Regression coefficient (b) based on Pauly test, was significantly different from ۳ in females, but not in males (p<۰.۰۵), indicating an isometric growth pattern in males and a positive allometric growth pattern in females and all fish.

Keywords:

Age , Growth patern , Length-weight relationship , Sex ratio