Date of Award


Publication Type

Master Thesis

Degree Name



Great Lakes Institute for Environmental Research


foraging, grouper, invasive, learn, lionfish


Hugh MacIsaac


Nigel Hussey




Understanding the way in which species forage, both alone and relative to heterospecifics and conspecifics, has important implications for ecosystem functioning. This is especially true for invasive species for whom context-dependent impacts make comprehensive impact assessments challenging. This thesis examined the foraging ecology of a marine invasive species to better assess its spatially and temporally-mediated impact. The goal of this thesis was to quantify the impact of lionfish (Pterois volitans) in an understudied part of its invaded range, both alone and relative to native analogues. I conducted feeding experiments to evaluate the way in which lionfish move about their environment and to assess the relative roles of behavioural plasticity, foraging efficiency, and cooperative hunting in foraging success. Lionfish showed flexibility in their ability to adopt spatial navigation strategies to remember the locations of profitable prey patches, durations for which lasted up to 6 weeks. Relative to native predators, lionfish exhibited similar consumption rates and lower per capita impacts, though combining their per capita impact with field abundance bolstered their ability to impact native prey populations. Lionfish displayed a high degree of gregariousness and were most efficient when foraging in pairs, whose consumption rates were mediated by the degree of refuge afforded to prey. Overall, these results suggest that the success of lionfish in the eastern Gulf of Mexico lies in the efficiency with which they forage, their behavioural plasticity, and their high population abundance relative to co-occurring native competitors. Understanding the impacts of invasive species is pivotal to managing their threat, though these understandings are contingent upon the assessment of impacts throughout the invaded range of a species.