Physical-Biological Coupling and the Challenge of Understanding Fish Recruitment in Large Lakes

Ability to understand and predict fish recruitment is a key goal of fishery management agencies in both freshwater and marine ecosystems. Toward this end, an increasing amount of recruitment-oriented research focused on the effects of physical processes on the early life stages of fish (e.g., eggs, larvae), as physical processes have been shown to directly and indirectly influence early life early life growth, survival, and future recruitment to the fishery. However, the majority of this research has been conducted in marine ecosystems when compared to freshwater systems, despite these ecosystems having similar physical processes and economically important fishes with life-history characteristics equally vulnerable to physical controls. Herein, we review the physical processes common to large lakes that may impact freshwater fish recruitment and address the current state of coupled physical-biological research for predicting fish recruitment in freshwater systems. Examples emphasizing the importance of physical forcing in regulating fish recruitment in the Laurentian Great Lakes are provided. Given the similarities in physical and biological components between ecosystems, we argue that understanding, predicting, and managing recruitment variation in the large freshwater lakes of the world will require coupled physical-biological research and modeling approaches that are more typical of marine studies.