Growth and reproduction of Bulatmai barbel Luciobarbus capito (Güldenstädt, 1773) in Gorganroud River of the Golestan Province- Northern Iran

Abstract

Bulatmai barbel (L. capito) is found in upper parts of most rivers of southern Caspian basin. In order to determine age, growth and reproductive characteristics of this species, a total of 318 specimens was sampled using beach seine in the Gorganroud River -southeast Caspian Sea from May to September 2017. WLRs were found as W=0.020TL^2.74 for females, W=0.016TL^2.80 for males and W = 0.234TL^2.84 for sex combined, indicating negative allometric growth pattern for the species in the area. The age ranged from 0⁺ to 8⁺ in females and 0⁺ to 7⁺ in males. Three growth models were fit to the data set and the Akaike information criterion (AIC) indicated that there were clear differences between the fitting models that were ranked the highest based on AIC selection or AIC weights and those based on model’s accuracy of length and growth parameter estimates. Considering AIC, L_t=667.63*[1-e ^{(-0.10*(t+0.14))}] and L_t=621.11*[1-e ^{(-0.11*(t+0.17))}] were best growth models for females and males respectively. The sex ratio was 1:2.38, highly unbalanced sex ratio. Considering GSI, the peak of reproduction was in May for both sexes. Absolute fecundity ranged from 1865.00 to 170940.00 with mean value of 26388.24, and relative fecundity had an average of 625.29. GSI and absolute fecundity related to fish size statically, while relationship between relative fecundity and egg diameter with fish size was no significant.