Swimming and hiding regardless of the habitat: prey fish do not choose between a native and a non-native macrophyte species as a refuge

The ability to respond to a predation threat may be the key factor influencing prey survival. Thus, small-sized fish may adapt to use macrophyte patches as refugia in ecosystems where they face predators. We evaluated the habitat choices of a small fish species (Serrapinnus notomelas) to determine whether these fish prefer native versus recently introduced submerged macrophyte stands in the context of predator avoidance. Specifically, we applied three predator cue treatments: no cue, chemical cue from a hungry predator and presence of a satiated predator. First, we empirically tested the theoretical assumption that the prey fish use vegetated habitats and that the presence of an actual predator has a stronger effect on the choice of habitat than simply a chemical cue. Then we tested the hypothesis that prey do not choose a habitat according to macrophyte species and whether this pattern changed as a result of increasing predation risk. We found that the prey fish preferred vegetated habitats; however, they did not appear to distinguish native from invasive macrophytes. Our results support the hypothesis that the physical structure of macrophytes is more important in determining habitat choice than the evolutionary relationship between the fish and the native macrophyte species.