Background. The life-history traits of non-native species are believed to change in a predictable manner in relation to time since introduction, with populations in the early stages of establishment predicted to invest more energy into reproduction than long-established populations, mainly due to lower intraspecific competition for resources. In Europe, the range of non-native pumpkinseed, Lepomis gibbosus (Linnaeus, 1758), continues to increase. Despite this, the majority of hitherto conducted studies have investigated long-established populations only, very few focusing on newly established populations (<10 years old) or comparisons of life-history traits of new and older populations. Materials and methods. In this study, we compared the fecundity, condition, and population structure of a new and a long-established pumpkinseed population (two- and 14-years after introduction, respectively) in two small central European lakes in order to identify any differences in life-history traits. Results. We confirmed that the established population displayed lower fecundity and poorer overall condition than the new population. Unexpectedly, there was no significant difference in size-at-maturity. Conclusion. While this study confirmed that life-history traits of introduced species appear to change with time since introduction, it also emphasises the possible effect of other factors such as temperature, size of body of water, and relative predator pressure in shaping such traits.

freshwater fish, alien species, introduced species, date of introduction, size-at-maturity, fecundity