Experimental evaluation of predation of stocked salmon by riparian wildlife: effects of prey size and predator behaviours

摘要: Predation after release is one of the major concerns hatchery fish conservation and propagation. However, relationships between size fish, predator species their behaviours in natural environments are largely unknown. To understand these relationships, we conducted predation experiments outdoor tanks a seminatural stream with exposure to local predators. Masu salmon (Oncorhynchus masou) two different classes were used as experimental prey present study. Camera trap data showed that grey herons (Ardea cinerea) primary system, most shallow areas morning or evening while feeding. Increasing density stocked led increases number occurrences heron. More importantly, by resulted significantly lower survival rate larger compared smaller salmon. The results indicate it important predators, adjust optimum body at choose appropriate stocking site time day for maximising effectiveness stocking.