The article touches upon the problems of breeding goldfish Carassius Auratus (L.), abundance of juveniles, size and age composition of the catches and the growth of this species in small rivers (for example, the Kazanka River and the lower reaches of the Sviyaga River) in terms of stocking the Kuibyshev Reservoir by goldfish. It has been stated that the process of stocking small rivers with goldfish has much in common with that in the reservoir. Spawning in the Kazanka in 2016 proceeded in two stages, and the gonads contained the roe of 2 portions. The first mass spawning took place from 11 to 20 May, and the second spawning – from 11 to 20 June. Macrophytes, driftwood and washed away roots of trees served as substrate for spawning. During the reproduction period of the species in the river the proportion of females made 75.0%, males - 25.0%. In the lower reaches of the Sviyaga in the period of 1998-2001 the proportion of males in catches made 26.1-65.7%. The maximum number of goldfish larvae and fingerlings in the lower reaches of the Sviyaga was observed in 2007-2009 and in 2014. These years had a similar regime of water level, but different temperature conditions in the spring period. Males in the catches had smaller sizes and body weight, compared with females. In the Kazanka in 2013-2016 the average body length of females in catches ranged within 16.7-23.8 cm, and males – within 15.9-20.6 cm. The age composition of goldfish in the river in 2013 consisted of 4-8 summer fish of 2006-2008 generations. Among them prevailed individuals at the age of 6 (53.1%) of the 2006 generation. In 2014-2016 in the catches there were fish aged 6-9 years old, although there were individuals up to 15 years old. The body length of the similar aged individuals of both sexes was not significantly different. Student criterion between both sexes at different ages ranged from 0.06 to 0.84. Growth of individuals of different generations in 2007-2010 also did not differ reliably. Thus, the average body size of 6- year-old fish of these generations ranged from 17.7 to 18.1 cm. The growth of goldfish in different reaches of the Kuibyshev Reservoir was higher than in the Kazanka, but Fulton fatness coefficient in the river was lower. The average values of the fatness coefficient ranged from 3.24 to 3.63 in the river, and in the reservoir reaches they are from 2.93 to 3.07.