Abstract
The visibility, activity, size and catchability of Calanus spp., herring larvae (Clupea harengus) and cod larvae (Gadus morhua) were quantified to reveal the importance of these prey characters on a predator's (Gobiusculus flavescens) prey choice. Detection probability was positively correlated with prey size, although, G. flavescens did not attack all the detected prey. Prey activity triggered predator attacks, while prey size and catchability had no effect. A rank test (order of prey detected or attacked) and a prey electivity analysis revealed a preference for the active herring larvae and Calanus spp., and a lack of interest for the less active cod larvae. Herring larvae being both the largest and the most active prey suffered the highest risk of predation. Although Calanus spp. were preferred over cod larvae, fewer Calanus spp. than cod larvae were eaten, due to Calanus spp. having a higher evasiveness. Cod larvae responded more frequently on predator attacks than herring larvae, but the herring larvae responded more sufficient.