Biological characteristics of bream (Abramis brama Linnaeus, 1758) of the Kremenchuk Reservoir as an object of commercial fishery
Authors:   National University of Life and Environmental Sciences of Ukraine, Kyiv, Rudyk-Leuska N. , Buzevych O. ,   Institute of Fisheries of the NAAS, Kyiv, Leuskyi M. ,   National University of Life and Environmental Sciences of Ukraine, Kyiv, Burjak I. ,   Institute of Fisheries of the NAAS, Kyiv
Published: December 2024

Purpose. Analysis of individual and population parameters of bream (Abramis brama L.) of the Kremenchuk Reservoir from the point of view for assessing the conditions for the formation and exploitation of the commercial stock of this valuable species in ecological and fisheries terms.

Methodology. Ichthyological material was collected in the spring and summer periods of 2021-24 from commercial catches. The total amount of analyzed fishing effort was 3210 net days, of which mass measurements were conducted on 12086 breams and 692 breams were collected for full biological analysis. The primary material was selected and processed according to generally accepted methods in ichthyology. Total mortality (Z) was determined graphically based on the natural logarithms of the number of age classes in terms of the effort of the standard order of gill nets, as the tangent of the angle of inclination of the regression line; natural mortality (M) of bream was calculated using the coefficients of the Bertalanffy equation.

Findings. The commercial catch of bream in the Kremenchuk Reservoir over the past 25 years has been characterized by instability with a significant decrease in 2020-24 - from 1.6-1.8 thousand tons to 1.1-1.3 thousand tons, while a decrease in the share of this species in the total catch was also observed - from 31-39% to 20-26%. The most abundant commercial contingents of bream of the Kremenchuk Reservoir were represented by individuals of 32-40 cm long, which resulted in relatively low average weighted values in 2021-24: age from 6.1 to 7.3 years, length from 33.3 to 36.8 cm, weight from 829 to 1080 g. The parameters of the von Bertalanffy equation, which characterize the growth rate for bream of the Kremenchuk Reservoir in the period 2021-2023, were: K = 0.119 (year-1), L∞ = 57.9 (cm) to = -0.77 (year), which is fully consistent with the values obtained in previous studies. The distribution of fishing effort by size and age groups of bream in the Kremenchuk reservoir during the study period did not fully correspond to the optimal values ​​in terms of specific accumulation of ichthyomas, which requires appropriate adjustment of the qualitative characteristics of the fish stock in this reservoir.

Originality. It is caused by the need to obtain up-to-date data on the state of self-reproducing populations with the determination and analysis of integral characteristics that affect the conditions of formation and exploitation of their commercial stock.

Practical Value. The obtained data were used to adjust the limits for the harvest of aquatic biological resources of the Kremenchuk Reservoir and fishery regimes in terms of regulating the fishing effort for 2025.

Keywords: Kremenchuk Reservoir, bream, size and weight, catch structure, commercial catch.