Age, growth and spawning season of Luciobarbus esocinus Heckel, 1843 in Gamasiab River, Iran

In the current paper reproductive strategy and growth rates of Luciobarbus esocinus were investigated from 2010 to 2012, in Gamasiab River, Kermanshah, Iran. Samples were collected seasonally by gillnet and electro-fisher device. Sex ratio was evaluated from 162 individuals and the percentage of male and female individuals were 54.76% and 45.24% respectively. Age structure was distributed between I and V and most frequency numbers for males and females belonged to II and IV age group, respectively. Length-weight relationship was computed as W=8E-05TL2.6546 for all individuals. Mean total length and weight was 333.82±13.10 mm and 297.67±4.85 g for males, and 371.5±21.17 mm and 307.85±7.64 g for females. The von-Bertalanffy growth models of L. esocinus were described as Lt =357.14×[1-e (-0.77× (t –0.090))] for males, Lt =367.02×[1-e (-0.78× (t –0.094))] for females and Lt =363.57×[1-e (-0.76× (t –0.087))]for both sexes. Results indicated that growth factors were highly similar in spring, summer and winter. CDA analysis revealed that the total and gonad weight are the main factors in discriminant analysis. The highest GSI values were found in spring for females and winter for males, however, it decreased rapidly after spring in females. Maximum growth rates were observed in early ages (I-II) and depleted with ages. K value and L∞ were determined as 0.77±0.09 Y-1 and 357.14±10.38 mm for males and 0.78±0.24 Y-1 and 367.02±24.15 mm for females, respectively. In conclusion this study provided basic information for stock assessment and management of L. esocinus in Gamsiab Reservoir.