My PhD research focuses on understanding spatial, predation, and population dynamics of two flatfish fish populations on the Grand Bank off Newfoundland. Despite decades of research focusing on the collapse of fish populations on the Grand Bank, we understand very little about how these populations changed across space and how changes in the ecosystem have impacted their ability to recover. My thesis consists of four chapters: 1) model changes in the spatial distribution of American plaice and yellowtail flounder and determine whether that change was environmentally driven, 2) develop a method for modeling the abundance of an important prey of these flatfish species (Northern sand lance), 3) use a juvenile population dynamics model to assess how natural mortality has has affected the unfished components of the American plaice population since their collapse, and 4) develop a model of intermediate complexity for American plaice and yellowtail flounder that can incorporate multispecies and ecosystem dynamics. My work will contribute to improving our understanding of the mechanisms that resulted in population collapse and lack of recovery to improve future management.