Size-dependent predation in piscivores: interactions between predator foraging and prey avoidance abilities

Body size is known to play a crucial role in predator-prey interactions. Fo r a given predator size, it has been suggested that prey mortality should b e a dome-shaped function dependent on prey body size. In this study, we exp erimentally tested (i) the suggested mechanisms responsible for the dome-sh aped prey vulnerability function and (ii) whether a prey refuge affected th e form of this function. As prey, we used young-of-the-year Eurasian perch (Perca fluviatilis), and as predator, larger Eurasian perch. The prey morta lity as a function of prey size was dome shaped for large and medium predat ors but decreased monotonically with prey size for small predators. Capture success of predators decreased monotonically with increasing prey size and was lower for small predators. in refuge trials, the mortality of prey dec lined monotonically with prey size for all predator sizes. Refuge use of pr ey increased with the sizes of both prey and predator. Our results suggest that the hypothesized dome-shaped relationship on prey vulnerability can be altered by the presence of an absolute prey refuge. Our results further su ggest that the ability to perform more flexible foraging behaviors is of in creasing importance when prey size increases.