Rutilus kutum is one of the most important economic fishes of the southern basin and Iranian coasts of the Caspian Sea. More than 5,000 tons of this fish are caught from this area every year, and more than 8,000 fishermen are engaged in catching it in the sea. In recent years, Iranian Fisheries Science Research Institute has sought to determine the bio-technique of its breeding in earthen ponds and rearing tanks for introduction to the country’s aquaculture industry and in this regard has started extensive research. In part of this research, the effect of density on the growth of this fish in earthen ponds was investigated. For this purpose, at the beginning of the spring season, at the temperature of about 14-16 oC, the broods artificially propagated, and the eggs after passing the incubation period and becoming active swimming larvae transferred to earthen ponds with a density of 1,500,000 per hectare. The fry were reared in these ponds until they reached the initial weight of about 0.897 ± 0.677 grams and were fed with special food for larvae and fingerlings (SFK) in addition to natural food. Then, they were transferred to fish breeding ponds with a density of 45,000 per hectare. The length of the rearing period in this stage was about 4 months and the fry were fed with formulated food with 43-46% protein and 10-14% fat. During the breeding period, health checks of the fish fry were carried out, the physical and chemical factors of the water, as well as the plankton and benthos organisms of the rearing ponds were measured and identified. The results showed that the weight of fry at the end of the breeding period reached an average of 17.07±1.99 and a maximum of 52 grams (fig. 1), so the yearling Kutum in the pre-breeding stage in the first year had a good growth in earthen pond.