Round goby movement patterns in a non-navigable river

Understanding non-native species dispersal is vital for their future management. The round goby (Neogobius melanostomus) has greatly extended its range since the 1990s, with commercial shipping being the main vector. However, our knowledge regarding their secondary dispersal from points of introduction is surprisingly limited. In this study, a series of field experiments were undertaken on a mid-sized river to assess goby dispersal patterns within an established population, following a simulated release of a large number of propagules, or at a simulated invasion front. Most of the established population remained stationary and just a few individuals undertook long-distance dispersal (principally upstream). Mean distance travelled was 1.1 m·day−1 (max. 29.6 m·day−1). While site fidelity appeared to last for most of the year (including winter), it was surprisingly relaxed during the spawning season. Concentrated release of a large number of propagules resulted in appreciably greater movement rates than in the established population, with upstream movement again dominating. In general, smaller, mostly male fish tended to move further and appeared as first colonizers in uninvaded areas.