School of BioSciences - Theses
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ItemHabitat preferences and fitness consequences for fauna associated with novel marine environments( 2017)The rapidly expanding reach of anthropogenic environmental change means that animals must now navigate landscapes comprised largely of modified and degraded habitats. Individuals that correctly perceive habitat quality will be best placed to survive and reproduce in novel environments, but where environmental change outpaces the evolution of behavioural responses, mismatches can arise between cues and the underlying value of habitats. These mismatches can lead individuals to select habitats that offer relatively poor fitness outcomes, creating ecological traps. In environments where ecological traps are likely to occur, data on habitat preferences and fitness consequences can fundamentally change predictions of metapopulation models and increase our understanding of the role that novel habitats play in population persistence, but such data are rarely collected. In this thesis, I first conduct a global meta-analysis to assess the state of knowledge on habitat preference and fitness metrics in animal populations, using wildlife populations associated with aquaculture as a case study. My findings reveal that responses to aquaculture vary widely across taxa and farming systems, ranging from large increases in abundance to near complete displacement. However, the influence of aquaculture on wildlife populations remains poorly understood, as researchers rarely obtain appropriate measures of habitat preference, survival or reproductive success. Accordingly, in subsequent chapters I apply the ecological trap framework to assess marine habitats modified by aquaculture or invasive species. In the first application, I collect wild Atlantic cod (a species known to be attracted to salmon farms) from areas of high and low salmon farming intensity, and compare reproductive fitness via a captive spawning trial with hatchery-rearing of offspring. I found limited negative effects of high farming intensity on quality of offspring. In the second application, I show that the threat of predation by a native keystone predator may limit the ability of an invasive seastar to exploit a food-rich habitat at shellfish farms. In the third application, I show that an invasive canopy-forming marine macroalga provides viable habitat for native fishes and may help to maintain fish biodiversity in areas where urban impacts have driven a decline in native macroalgal canopy cover. Together, this thesis demonstrates the utility of individual-level data on habitat preference and fitness outcomes—via the application of the ecological trap conceptual framework—in assessing the impacts of novel habitats on animals, and recommends greater use of this approach in future investigations into the impacts of human-induced rapid environmental change in coastal marine ecosystems.