Range expansion dynamics of the invasive round goby (Neogobius melanostomus) in a river system

The rates of upstream and downstream range expansion of the round goby (Neogobius melanostomus) were examined in the Trent-Severn Waterway in 2009 and 2010. Relative abundance, demographics, and habitat use were also compared between areas of range expansion and a longer established area to determine how these characteristics varied along the invasion pathway. Round gobies were sampled using an angling removal method in May and August of 2009 and 2010 at 75 sites at each area of range expansion and 25 sites near the center of their range where they first became established in the waterway. Areas of range expansion had initially low abundance and low site occupancy in May 2009 relative to the longer established area. Large increases in abundance and site occupancy were observed over the first summer of occupation, but with limited range expansion. Rapid range expansion was observed during the non-reproductive season at the upstream edge of range. Individuals sampled in the expanded upstream range were small and female biased relative to other range locations. Round gobies also exhibited higher habitat selectivity for rocky substrates at range edges than in the longer established area. These characteristics of seasonal dispersal, biased demographics of dispersers, and high habitat selectivity may be important components of successful range expansion of the round goby in invaded ecosystems.