Some peculiarities of the reproduction of stone moroko (Pseudorasbora parva Temminck & Schlegel, 1846) in a pond fish farm of the Polissya zone of Ukraine

Purpose. To establish the fecundity and maturity stages in different portions of stone moroko eggs during preparation for the wintering period in the invaded area - in the conditions of pond fish farms of the Polissya zone. Methodology. The material was collected in the fall of 2022 in ponds of a fish farm located in the Polissya zone. Namely, in the village of Lany-Sokolivski, Lviv region, with water supply from the Sukil River, which belongs to the Dniester River basin. A sample of stone moroko (240 individuals) was selected using a lift net, the standard length and weight of each fish was measured, the sex was determined, scales were collected to determine age, and eggs from females were collected for further fertility studies. Fulton’s and Clark’s condition factors, gonad-somatic index and the number of eggs at different stages of maturity according to Shikhshabekov were calculated [27]. Findings. The gonadosomatic index ranged from 0.25% to 6.62%. At the same time, the values ​​of GSI in males were significantly lower than those in females, which coincided with the data for other water bodies. With age, GSI values ​​decreased for both sexes. The absolute fecundity of stone moroko females ranged from 129 to 1388 eggs, the average value of the individual absolute fecundity index (IAP) was 630.8 eggs. The absolute fecundity of age-2+ fish was 416.4; age-3+ – 569.3; age-4+ – 959.9. For all age groups, the largest number of eggs belonged to the D1 maturity stage. Mature eggs of stage E were the least represented, which was due to the end of the spawning period at the time of sampling. Originality. For the first time, in aquaculture conditions, the reproductive performance of the stone moroko was assessed before the start of the wintering period in a fish farm pond. Practical Value. The stone moroko is one of the most successful invasive fish species in freshwater bodies of Ukraine but data on the characteristics of its reproduction is scarce. Understanding the characteristics of the reproduction of invasive alien species is key to being able to assess their further spread and counteract it.