Biological justification for fish harvest limits in the Zaporizhzhya (Dnipro) reservoir for 2017

Purpose. To analyze the current state of the populations of roach, bream, pikeperch and silver bream in the Zaporozhye (Dnipro) reservoir and to determine the acceptable amounts of commercial harvest of these fish species for 2017 by determining scientifically justified limits. Methodology. The summarized results of ichthyological studies conducted during 2010–2016 years were used during the research. The materials were collected in the Zaporizhzhya (Dnipro) Reservoir using standard fish sampling methods. A set of standard fishing gears (gill nets with mesh sizes of 30–120 mm) was used for studying fish fauna. Juvenile fish were caught in the third decade of July – first decade of August using a beach seine of 10 m in length. The processing of collected samples was conducted by conventional methods. Findings. We studied the current state of commercial fish populations, the exploitation of which is limited (roach, bream, pikeperch, silver bream). We determined the basic biological parameters of these species, determined the age and sex structure of their populations and assessed their stocks. Based on these data, we determined the rates of natural, fishing and total mortality and calculated the amounts of commercial catches of the investigated fish species. With an optimum catch of the roach not exceeding 25% of the calculated stock, we recommended to set a limit on the catch of this species for 2017 as 190 tons. Next year, it is advisable to set a limit for the bream catch not higher than 88 tons. Due to a critical state of the pikeperch stock in the Zaporozhye (Dnieper) reservoir, the recommended limit of its catch for 2017 should not exceed 14 tons. The estimated catch limit for the silver bream for the following year is recommend to be 70 tons. The harvst of these fish species within the proposed limits will allow carrying out their commercial exploitation without environmental damage. Originality. We presented the results of the study of the stat of commercially important fish populations, the harvest of which is limited annually. These approaches to the commercial harvest of the roach, bream, pikepearch and silver bream are aimed at introducing and implementaing the scientific justification of commercial fish exploitation in the Zaporozhye (Dnipro) reservoir. Practical value. Determination of the proposed commercial harvest limits for the roach, bream, pikeperch and silver bream ensures a rational use of aquatic living resources and conservation of the stocks of the commercial fish species in the conditions of fishing pressure.