Reproductive traits of the invasive round goby (Neogobius melanostomus) along a latitudinal span in Europe.

Abstract

The Ponto-Caspian region is a hotspot of the successful establishment of non-native species in freshwater ecosystems, with the round goby Neogobius melanostomus being a notorious example. However, comparing data on its reproductive biology is complicated due to differing data collection methods, traits examined, and sampling times. To address these inconsistencies, we conducted a study of five established round goby populations across a broad latitudinal range in Europe during a similar period adjusted to the species’ spawning period. The sample included 83 female round gobies from Türkiye, Croatia, Slovakia, Poland, and Finland. We compared reproductive traits, including absolute, batch, and relative fecundity, oocyte size, and gonado-somatic index (GSI), as well as body condition factor. Relative fecundity and condition factor exhibited an interesting pattern, indicating high reproductive investment in the Turkish population through significantly higher values of relative fecundity and lower condition factor compared to other populations. Although no significant differences in GSI values were found among populations, a trend was observed, with the highest values in Türkiye and the lowest in Finland. Generalized Linear Modeling revealed that relative fecundity was positively associated with latitude but negatively influenced by condition. Our findings support the suggested high phenotypic plasticity, particularly in this life-history trait.