Considering the large population of kilka in the Caspian Sea and their role in the survival of ecosystem, it is important to know their biological characteristics as a basic information in the fisheries research activities. The project was conducted to evaluate the biological characteristic of these fishes including: reproduction and fecundity rate, relative frequency percentage, age and weight composition and diet. 1000 fish samples from three different species of Clupeidae 1 - Clupeonella cultriventris (common kilka) 2 - Clupeonella engrauliformis (anchovy) 3 - Clupeonella grimmi (big eye kilka) were studied from November 1993 to November 1994. The study indicates that C. cultriventris starts its spawning in the beginning of spring, C. engrauliformis spawns in the middle of summer and C grimmi has a longer spawning period (once starts in the beginning of autumn and the second period starts at the end of winter). Anchovy has the most relative frequency, the average of absolute fecundity for anchovy and big eye kilka are 32847 ± 10150 and 17892 ± 3916, respectively