Reproductive characteristics of the blue bream Ballerus ballerus (Linnaeus, 1758) of the Kama reservoir

This paper presents the age and sex structure of the spawning part of the blue bream population in the Kama reservoir in 2019-2022. The age structure of the blue bream is characterized by a high number of older groups, which is associated with the peculiarity of fishing in the Kama reservoir. In comparison with earlier data on the reservoir, a reduction in the timing of fish puberty has been established, currently timed to the 5-year-old age for males, and to the 6-year-old age for females. It was revealed that the life expectancy of fish increased to 17 years of age. A study of fertility of blue bream was carried out on 87 females represented by 11 age groups. The limits of variation of individual absolute fecundity have been determined to exceed the earlier data, the minimum of individual absolute fecundity is 8.6 thousand eggs, the maximum of individual absolute fecundity is 78.8 thousand eggs. It is shown, that the reproductive ability of the females of the blue bream in the Kama reservoir remains at a high level and is characterized by increase in the average values of individual relative fertility up to 10 years of age, the maximum average values of relative fertility are observed in 15-year-old fish.