Date of Award


Publication Type

Master Thesis

Degree Name



Great Lakes Institute for Environmental Research


Cohort, Coral trout, Fishing pressure, Genetic diversity, Genetic drift, Natural selection


Daniel D. Heath




Many reef fishes are harvested, making it important to study the effects of exploitation. However, reef fishes often show highly variable and unpredictable genetic patterns, and high levels of gene flow from dispersive larvae can mask the effects of stressors. Since larval dispersal is the main mechanism of gene flow in reef fishes, and inter-reef movements of adults are reduced, studying cohorts offers a solution to assessing the effects of exploitation because it lowers the chance that gene flow will mask the effects of fishing. Here we characterize genetic patterns in the common coral trout, Plectropomus leopardus, an important reef species that is exploited across the Great Barrier Reef. Since larval dispersal is the main mechanism of gene flow in this species, we were able to use a cohort approach to observe genetic patterns at the cohort level and assess how these patterns contribute to the those at the population level. Additionally, decreased gene flow in adults allowed us to characterize the effects of line fishing without dispersal masking the effects. We also present a candidate-loci approach to detect selection in 8 populations of coral trout, allowing us to assess the role of selection in shaping genetic patterns, and identify SNP loci impacted by fishing. We found evidence for variation in genetic structure of coral trout and showed fishing had no impact on neutral genetic diversity, but impacted the average relatedness within populations, indicating that certain families survive fishing pressure more than others. We also identified SNP loci under selection likely as a result of fishing pressure, including those immune, thermal stress, and metabolism genes. We successfully implemented a cohort approach to assess the effects of fishing in this important species. Overall, we have shown that both selection and genetic drift shape genetic structure of this exploited fish.