Abstract

Most animals are at some point in their development required to perform behaviours under the threat of predation. There is a need to trade off behaviours like foraging and territoriality with anti-predator behaviour in order to maximize survival. Recent studies have shown that Atlantic salmon potentially compensate for chronic predation risk by reducing territory size but maintaining the same growth rate. However, no direct measures of foraging or growth were collected. Here, I tested the hypothesis that juvenile Atlantic salmon can adjust behaviours depending on the perceived risk of predation. I conducted trials under semi natural conditions in which the experimental group was exposed to alarm cue and the control group to stream water over two field seasons in 2010 and 2011. Territory size was recorded on Day 1 and Day 7 while foraging was recorded daily for as many individuals as possible. The change in weight between Day 1 and Day 7 was also recorded for every individual. Overall, I found that territory size reduced over the seven day period for the alarm cue group while foraging and growth did not differ significantly between treatments. However, there were significant differences in results over the two field seasons. These results suggest a behavioural compensation between territory defense and foraging under the effect of chronic predation. The differences in response by year can be explained by looking at the resources dynamics of each year. Future work could examine this influence further.