| The introduction of non-native species is one of the most critical factors contributing to
the decline and extirpation of native organisms worldwide. Cutthroat trout
(Oncorhynchus clarkii), native to western North America, are commonly displaced by
invasive brook trout (Salvelinus fontinalis). Higher aggressiveness and the ability to
forage under low light conditions are characteristics of brook trout that could significantly
influence whether this species can out-compete cutthroat trout. In this study, I evaluated
levels of aggression and foraging behavior of cutthroat trout and brook trout to assess
differences in competitive abilities in these two salmonid species. Behavioral
observations from pairwise contests in an experimental arena were used to test for
differences in aggression, ability to defend a feeding station, and the amount of food
captured under conditions of high and low light intensities. I found brook trout were most
aggressive towards other brook trout, captured more food items in high light treatments,
and held feeding stations longer than cutthroat trout. However, brook trout were not
superior nocturnal foragers. My study indicates that while aggressive behavior and
nocturnal foraging may contribute to brook trout success over native cutthroat trout,
population and individual-level factors that drive patterns of extirpation observed in
sympatric populations warrant further study.
Key Words: invasive species, cutthroat trout, brook trout, competition, foraging ecology,
behavior |