PREDATOR AVOIDANCE IN NAIVE AND EXPERIENCED JUVENILE CHINOOK AND COHO SALMON

We compared the vulnerability of naive and experienced coho and chinook salmon to predation by rainbow trout and related these findings to observations of the specific behaviour of each species during an encounter with the predator. Naive chinook were significantly less vulnerable to capture than naive coho in an open field encounter but there was no difference in capture rate of experienced coho and chinook. In videotaped encounters we found that coho and chinook behaved in significantly different ways when attacked by the predator, both when naive and when experienced. Our results suggest that predator avoidance strategies are highly species specific, that both species adjusted their behaviour after experience with the predator, and that the behavioural changes adopted by coho improved their ability to avoid the predator in an open field but those adopted by chinook did not. Considerable recent research has explored the willingness of different species, sexes, or life stages to risk exposure to a predator to obtain some reward (usually food). Our results further suggest that published experiments that purport to demonstrate differences in risk taking among types of prey may, instead, demonstrate differences in predator avoidance capability.