The effects of sea lice on juvenile pink salmon predation susceptibility

Juvenile pink salmon (Oncorhynchus gorbuscha) infected by sea lice (Lepeophtheirus salmonis) are known to be more susceptible to predation, but the mechanisms by which this occurs are unknown. This thesis used a predation risk framework to understand how L. salmonis may increase juvenile pink salmon predation susceptibility. Infected juvenile pink salmon increased their exposure to predators by returning sooner after a simulated heron attack when infected with a single adult louse. However, when attacked by a model heron, they appear to be equally likely to escape as non-infected fish. When infected with adult female lice, juvenile pink salmon were not able to swim as far in a swim tunnel against a gradually increasing current; suggesting a reduced condition. The effect of infection on condition is a potential driver of the increased risky behaviour (exposure) and has broader implications for predation susceptibility and for juvenile pink salmon early marine survival.