Length-weight relationships and sex ratio in populations of topmouth gudgeon (Pseudorasbora parva) in Ukraine and Slovakia

Pseudorasbora parva was first documented in Europe in 1961 and spread across Eurasia in less than 40 years.Its rapid expansion can be attributed to its opportunistic life history traits.Current data on P. parva life history in Ukrainian populations are incomplete.However, some information is available from Slovak populations.Samples of P. parva for the current study were collected from canals, rivers, and fish farms in Ukraine and Slovakia to analyze population age structure and growth.A total of 1244 specimens (563 from Slovakia, 681 from Ukraine) were analyzed.Standard lengths ranged from 13 to 71 mm, while weights varied between 0.01 and 7.4 g.The populations comprised age groups from 0+ to 6+.P. parva reached reproductive maturity at age 1+ and lengths of 35-40 mm in Slovakia, and at age 1+ with lengths 30-40 mm in Ukraine.In both Ukrainian and Slovak fish farms, older age groups were more common.In habitats with natural food supply (rivers, irrigation canals) younger age groups (0+ and 1+) predominated.