Assessing the efficacy of spring stocking of pikeperch (Sander lucioperca) into a eutrophic reservoir

Abstract

Jůza T, Blabolil P, Čech M, Draštík V, Holubová M, Kočvara L, Kubečka J, Malinovskyi O, Policar T, Rychtecký P, Říha M, Sajdlová Z, Tušer M, Vašek M. 2024. Assessing the efficacy of spring stocking of pikeperch (Sander lucioperca) into a eutrophic reservoir. Lake Reserv Manage. 40:196–204. The survival of stocked fish is one of the crucial problems of management measures. In April 2023, approximately ten thousand 1-yr-old pond-reared pikeperch fry were marked and stocked into the small, eutrophic Hubenov Reservoir in the Czech Republic. Later that year, in August, the abundance of the stocked pond-reared pikeperch in the reservoir was estimated through beach seining, electrofishing, and gillnetting. Gillnet results showed that pikeperch avoided pelagic and deeper benthic habitats. Consequently, the most quantitative results were obtained by night beach seining. Our captures indicated that approximately 688 stocked pikeperch individuals were present in the entire reservoir in August, representing 6.5% of the stocked fish. These pikeperch displayed good growth and condition, primarily feeding on European perch fry, the most abundant 0+ fish in the reservoir. Our findings elucidate a relatively high mortality of 1-yr-old pond-reared pikeperch in the reservoir after spring stocking. Despite this mortality, the stocked pikeperch represented 85% of all 1-yr-old pikeperch in the reservoir. This highlights the effectiveness of spring stocking as a valuable tool for supporting the pikeperch population in reservoirs, emphasizing the stocking of an adequate quantity of pond-reared fish to compensate for the observed mortality.