Reproductive biology of Mossul bleak (Alburnus mossulensis) in Bibi-Sayyedan River of Tigris basin in Iran

Reproductive characteristics of Mossul bleak, Alburnus mossulensis, a native species of Cyprinidae family in Bibi-Sayyedan River of Semirom, Isfahan, were investigated by monthly sampling during December 2010 to December 2011. Five hundred and fourty three specimens (256 females, 159 males and 31 immature) were caught by a sein net (5 mm mesh size). The collected sampeles were anesthesized in 1% clove oil solution and transported to the laboratory on ice and subjected to dissection and biometric measurments. Age of males and females ranged from 0+ to 5+ years. The sex ratio was 1M: 2.2F (p < 0.05). The females outnumbered the males in all age classes. The largest female was 16.8cm in total length and 49.12g in weight and the largest male was 14.1cm in total length and 28.19g in weight. The age and total length at first maturity of females and males were estimated as 1 year and 5.3cm total length, and 2 years and 4.4cm, respectively. The minimum, maximum, and avarge absolute fecundity were 2064, 10316, and 5505 ± 2686SD, respectively and also, the relative fecundity was 203 ± 58 egg/g body weight. Macroscopic analysis of gonads and gonadostomatic index (GSI) values suggested that spawning ofA. mossulensis occurs from March to June with a peak in April. Thus, A. mosullensis is considered a group-synchronous type species with a capacity for multiple ovulations within a reproductive season (multiple spawner).