To boldly go where no goby has gone before: boldness, dispersal tendency, and metabolism at the invasion front

The successful establishment and expansion of invasive species may be linked to the behavior and dispersal tendency of individuals within an introduced population. To test the prediction that the boldest individuals, with the greatest dispersal tendency would be concentrated in the area of active range expansion, we compared the behavior, dispersal tendency, and metabolic rate of male round goby (Neogobius melanostomus) sampled from the expanding edge of their range with those sampled from an established area in the Trent–Severn Waterway, Ontario, Canada. Behavior and dispersal tendency were assessed in an artificial flume at 2 different water velocities using individuals caught in the spring and autumn of 2013, while resting metabolic rate (RMR) was determined using intermittent flow-through respirometry on fish collected in the autumn only. Round goby from the edge of their expanding range emerged from a shelter sooner, moved farther and faster in the flume, and had higher RMRs than individuals from established areas within the river. Neither water velocity nor season of capture was important in explaining the variation in time of emergence or movement. The higher proportion of bold individuals with high dispersal potential at invasion fronts facilitates further dispersal of round goby populations, and could help explain the rapid expansion of this species in North America and Western Europe. However, the benefits of bold phenotypes in terms of dispersal may be offset by increased energetic costs while at rest.