Persistence of an invasive fish (Neogobius melanostomus) in a contaminated ecosystem.

Post-establishment dynamics of invasive species have been under-studied. However, understanding these dynamics is particularly important for the management of invasive species known to impact native communities. Following the invasion of a highly invasive species, the round goby (Neogobius melanostomus), we document long-term population changes after establishment and address how population dynamics of a successful invader change through persistence and integration. Round goby present a threat to the areas they invade by out-competing native species for resources. Furthermore, as a pollution tolerant species, round goby present a second threat by acting as a possible vector for contaminant transfer to higher trophic levels in invaded ecosystems with areas of contamination. We sampled round goby for 11 years (2002–2012) at four low contamination sites and two high contamination sites within Hamilton Harbour ON, Canada, an International Joint Commission Area of Concern. Across sampling years, we show that round goby abundance has declined at low contamination sites, while remaining stable at high contamination sites. Moreover, we show that average body size decreased and reproductive investment increased both across sampling years and between sites of low and high contamination. Our results document population demographic shifts in a persist- ing invasive species, and underscore the importance of management practices for this species in contaminated environments.