Crude oil and its associated by-products are ubiquitous in the aquatic environment due to both natural and anthropogenic sources (i.e. oil seeps and rivers flowing over surface bitumen, and pipeline ruptures, grounded ships, storage tank leaks and tailing pond seepage, respectively). This diversity in sources gives rise to a large family of complex contaminant mixtures, including weathered and unweathered oil, unconventional oil, such as diluted bitumen (dilbit), and crude oil extraction-based mixtures, such as oil sands process water (OSPW). The main objective of my research is to explore the effects of crude oil and oil extraction-related contaminants on ecologically relevant behaviours in both fresh and saltwater fishes. My research objectives are distributed across three contaminant-based studies: i) the impact of weathering and dispersant application on crude oil toxicity to fresh and saltwater fishes, ii) a comparison of diluted bitumen (unconventional crude oil) and conventional crude oil toxicity to freshwater fish, and iii) the effects of raw and ozonated OSPW on freshwater fish. These objectives can be broken into three areas: 1) characterization of toxicity of various crude oils and oil extraction-based contaminants to early life stages; 2) exploration of any lasting impacts of crude oil and oil extraction-based contaminant exposures on a diverse array of ecologically relevant behaviors; and 3) the determination of fish avoidance responses. Ecologically relevant behaviours may serve as sensitive indicators of toxicity, ones that will provide a more in-depth characterization of complex contaminant mixtures and their effects on fitness.