The article analyzes the data of long-term studies of sterlet growth in the Kuibyshev Reservoir (watershed of the Volga River) conducted by researchers of the Tatar branch of the All-Russian Research Institute of Fisheries and Oceanography. Significant variations in sterlet length were found not only from year to year, but also in different parts of the reservoir. There have been stated the changes in sterlet population. In recent years, the reservoir has seen an improvement in the growth of sterlet yearlings in comparison with that of fish in the Volga river and in the first years of the reservoir's existence, and a decrease in the growth rate and size of older individuals. It has been found that starlet species in Kama Reaches grow better than in other parts of the reservoir. Fish with fast linear growth is found to increase its percentage, while the part of slow-growing fish decreases.

The article provides a description of the complex pneumatic fish protection structure (FCS) of the pumping station No. 1 of the Karmanovskaya GRES. Estimated design flow rate of NS No. 1 of water intake is 44 m3/s. The RGU includes an impenetrable screen in the form of a zapan, covering the surface two-meter layer of the water intake flow and a pneumatic (water-air) curtain that provides protection for fish fry of various sizes living in the thickness, surface and bottom layers of the reservoir. Ichthyological studies conducted by the Tatar branch of the Federal State Budgetary Scientific Institution "VNIRO" showed that the complex pneumatic fish protection structure protects juvenile fish living in the reservoir with an average efficiency of 86.51%, which exceeds the regulatory requirements of 70% of the current SP 101.13330.2012 (updated edition of SNiP 2.06.07 -87 "Retaining walls, shipping locks, fish passage and fish protection structures" (as amended No. 1).

The article presents a review of the main commercial fish stocks of the Kuibyshev Reservoir based on the long-term research data (2000–2019). The Kuibyshev Reservoir is the leading fishery reservoir in the Republic of Tatarstan, Mari El, Chuvashia, Ulyanovsk and Samara Re-gions. There have been given the data of regular observing species, sex, size-weight and age composition of fish, their reproduction efficiency, distribution, abundance and reproduction of aquatic biological resources, their habitat, as well as control over their fishing and conservation. The analysis of the influence of environmental factors (level and temperature regimes) and fishing on the fish stocks formation is presented. Based on the presented materials, there have been shown the data about the stocks of the main commercial fish species of the Kuibyshev Reservoir (bream, zander, pike, carp, catfish, sterlet) and of the small-sized ordinary fish stocks, the optimal development of which will bring the catches up to 10 thousand tons and more. It has been inferred that for rational fishing in the reservoir, it is necessary to develop a strategy for the integrated effective development of biological resources of the reservoir on an ecosystem basis for better use of the bioproduction capabilities of its biological resources.

В статье приводятся данные многолетних исследований популяции стерляди Куйбышевского водохранилища и изменения, произошедшие в ее структуре. Анализируются биологические показатели стерляди Куйбышевского водохранилища последних десятилетий в сравнении с таковыми предыдущих лет исследований. Исследование вылова стерляди в Куйбышевском водохранилище выявило, что по сравнению с данными прошлых лет промысловый вылов ее значительно уменьшился. Стерлядь является объектом браконьерского лова и редко сдается на приемные пункты. Основу численности уловов в 2012–2019 гг. в Волжском, Камском и Волжско-Камском плесах, как и по всему водохранилищу, составили рыбы абсолютной длиной 30–45 см. Рыбы промысловой длины 42 см (абсолютная длина 47–48 см) и более составили 4 % от общей численности выборки. В наших уловах по численности преобладает стерлядь массой 150–300 г. Отмечено отсутствие рыб старше 10-летнего возраста, увеличение линейных размеров у 3–5-годовалых особей и численное преобладание самок над самцами. По размерно-весовым показателям у рыб отмечается половой диморфизм. Выявлено, что самки стерляди Волжского плеса Куйбышевского водохранилища, находящиеся на II жировой стадии половой зрелости, растут интенсивнее, чем самки с отсутствием отложения жира в гонадах. Материалы, полученные в ходе исследований, имеют важное практическое значение для рационального рыбохозяйственного использования и природоохранное значение для существующего биоразнообразия. Результаты исследований позволяют оценить современное состояние популяции стерляди как одного из ценнейших представителей семейства осетровых Волги и ее водохранилищ.

The article gives general description of perch population of the Kuybyshev reservoir according to the net fishing in 2014-2017, as well as comparison of the results with literature data. The maximum perch specimen caught during the years of research had a body length 40 cm, weight over 1.5 kg and age of 13 years. Maximum life span of perch in the Kuibyshev reservoir has been calculated, which is 17 years. The prevalence of females over males in the populations of perches with the ratio 2:1, the average age of sexual maturity of females and males coincides and makes 3 years. The decay of the reproductive function of the perch occurs after 5 years. Massive spawning of perch in 2016 was observed in the water with temperature 10°C. The maximum value of individual absolute fertility in perch was 370.3 thousand eggs. Differences in the rate of perch growth in various parts of the Kuibyshev reservoir were revealed. A total fish mortality rate made 0.6. The calculation of the catch of perch by the amateur fishermen was made within the Republic of Tatarstan, which amounted to 1.6 tons in 2016. The data of the Tatar department of the State research institute of fisheries "GosNIORH" on the commercial catches of perch in the Kuibyshev reservoir have been presented.