Features of the growth rate of silver carp (Hypophthalmicthhys) in reservoirs of the Volga Upland within Penza region

Abstract

Background. The silver carp, by its nutritional value, high growth rates, nutrition due to the natural forage base, acting as a biological reclamation of water reservoirs, is the most promising object of aquaculture for water reservoirs of complex purpose of the Volga Upland. In Penza water reservoirs, silver carp are constantly released at the age of larvae or one-year-olds from fish hatcheries, mainly in other regions. Unlike pond farms, reservoirs of complex purpose are not drained almost completely, while partial catch of commercial fish and replenishment of stocks with fish planting material are regularly carried out.And if the growth rate of the silver carp in fish ponds is reliably known until the age of three, the growth rate of the larger silver carp and the silver carp in general in reservoirs of complex purpose has not been studied. The purpose of this work is to study the growth rate of silver carp in the reservoirs of the Volga upland within Penza region. Materials and methods. Large specimens of silver carp from various reservoirs of Penza region from 2010 to 2022 were analyzed. Due to the small size of the fish scales and the blurring of the annual rings, which made it extremely difficult to measure distances on the fish scales using an ocular micrometer, an original research method was used to qualitatively assess the age. A photograph of the scales taken through the eyepiece of a microscope was transferred to a computer, processed and examined using the toolbar of typical programs. The growth rate of the fish was determined by inverse calculations using the Rose Lee formula. Results. When estimating the size of a silver carp by scales, the longitudinal and transverse diameter of the scales can be used. In reverse calculations, it is permissible to use any sector of fish scales with the most pronounced annual rings. There were no visible differences in the growth rates of silver carp from various reservoirs and districts of Penza region.No differences were found in the rates of linear growth of white and variegated silver carp. The weight growth rate of the commodity variegated silver carp is 20-30% higher than the white one. In contrast to the white silver carp, characterized by a fairly even growth rate of the same age groups when grown in ponds, the weight of the variegated silver carp varies significantly both in one generation and in different years in the same reservoir.The maximum increase in the length of the white and variegated silver carp is noted at the age of 2 years, in subsequent years the increase decreases. The annual weight gain increases with age. Regression formulas are constructed on the basis of the revealed dependencies of growth indicators. The dependences between the length and body weight of both types of silver carp are most optimally approximated by a power function, the rest by quadratic regression. Compensatory growth of the silver carp was noted. Conclusions. The technique given in the work allows for more reliable reverse calculations of fish growth by scales. In various reservoirs of the region as a whole, the silver carp is characterized by an equal growth rate, which makes it possible to reliably plan the production of its products. Taking into account the constant weight gain by age, it is advisable to leave the silver carp for rearing for a number of years. Taking into account the largest annual gain among all the inhabitants of the region’s fish in reservoirs of complex purpose, fish ponds without the need for artificial feeding, the silver carp remains the most promising object of aquaculture in the region.

Keywords

• white silver carp
• variegated silver carp
• scales
• reverse calculations
• growth rate
• reservoirs