Modeling approaches to understand fish recruitment in large lake ecosystems

Fish population abundance and age structure is primarily determined through annual recruitment success (i.e., early life growth and survival through periods of heightened vulnerability). Many physical and biological processes contribute to fish early life growth and survival. Determining the relative contribution of these to annual recruitment variation is challenging owing to the multiple scales across which highly variable processes influence early life growth, mortality, and eventual survival. Elucidating these mechanisms are increasingly complicated by climate change and various anthropogenic stressors as conditions deviate from historic baselines. Thus, while traditional correlative approaches are often sufficient in explaining broad-scale patterns in historic recruitment variation, they are often unable to elicit processes at finer scales of potential importance and forecast future recruitment potential under climate change. Approaches that a) leverage mechanisms withstanding more than a century of research, and b) attempt to account for spatial and temporal scale-dependencies may promote a new understanding of conditions structuring annual patterns in recruitment and advance forecasting of future recruitment potential. Here, we used statistical and mechanistic modeling strategies to explore patterns in alewife and yellow perch recruitment in large lake ecosystems (i.e., the Laurentian Great Lakes). In chapter 2, we investigated nonstationary shifts in yellow perch stock-recruitment relationships in Saginaw Bay, Lake Huron. In chapter 3, we explore climate-induced physical transport phenologies of larval fish and consider the consequences of transport to experienced thermal conditions and encountered prey availability. Finally, in chapter 4, we investigated spatial scales of recruitment variation in a large lake to understand the relative influence of fine-scale asynchrony in structuring broader patterns in historic and potential future recruitment potential.