When is it good to be shy? Experimental evaluation of predation of juvenile salmon by riparian wildlife

摘要: Animal behaviors are often well adapted to their environments. Predation risk avoidance is one of them. However, the fitness effects behavioral variation associated with predation risks poorly understood for aquatic organisms. In this study, we evaluated traits (origin and body size) (regular defensive post-stimulus behaviors) masu salmon [Oncorhynchus masou (Brevoort, 1856)] on risk. We first conducted aquarium experiments examining fish, followed by an evaluation survival after release in a semi-natural stream. After 56 days stream test, 48.3% released fish were lost. On-site camera trapping identified ambush predator, grey heron (Ardea cinerea Linnaeus, 1758), as most frequently visiting predator. By individually matching test stream, found that critical determinant was regular behavior (i.e., hiding when they NOT exposed mimicked bird attack), rather than behavior. Our results indicate can be beneficial prey survival, at least faced predators.