Description of the biology of Caspian vimba, Vimba vimba (Linnaeus, 1758), in Gorgan Bay-Miankaleh Wildlife Refuge (southeast Caspian Sea)

We collected Vimba vimba throughout the spawning season (mid April to mid June, 2007) in Gorgan Bay (south-western Iran) and investigated its age, growth, and reproductive traits. The maximum age was 5⁺ years. Both sexes grew allometrically (positive for males: b=3.140 9 and negative for females: b=2.791 4). The von Bertalanffy growth functions were described by the formulae L _t =32.565(1-e^{−0.184(t+0.530)}) for males and L _t =35.950(1-e^{−0.179(t+0.529)}) for females. The overall sex ratio was balanced, but males were predominant in the smaller size classes and females in the larger size classes. Based on the gonadosomatic index (GSI) values, spawning appears to occur between late April and late May in the bay. The highest mean GSI was 6.44 for males in early May and 20.36 for females in late April. Absolute fecundity varies from the minimum of 5 436 eggs for age 3⁺ fish to the maximum of 36 141 eggs for age 5⁺ fish. Fecundity was also positively correlated with fish size (length and weight). Egg diameter ranged from 1.05 to 1.70 mm in the mean of 1.42 mm. There was no correlation between female size and ova diameter.