Chapter 13: Ecology and Management of Lake Food Webs
Steven R. Chipps and Brian D. S. Graeb
Knowledge of factors that affect lake productivity, species interactions, and energy flow in aquatic food webs has increased appreciably in the last half century. Contributions from the fields of fisheries science and limnology, along with technical and analytical advancements, have provided fisheries managers with new insights and tools to evaluate fish populations. Resource managers now recognize that stocking or removing certain fishes (i.e., biomanipulation) can have an important influence on food web structure and resulting water quality. Similarly, energy-based analytical techniques, such as stable isotope analysis, are increasingly used to supplement traditional diet studies.
In many ways, movement toward food web-based research and management strategies represents a shift in the traditional paradigms of fisheries biologists and limnologists. Not long ago, fisheries management and limnology were guided by different paradigms (Rigler 1982). Fisheries managers, because of their emphasis on stock–recruitment relationships, adult survival, and fishing pressure, often ignored factors such as lake productivity or species interactions. In many cases, fishing mortality was the driving variable of their predictive models. Limnologists, on the other hand, believed that the appropriate scale to study was the whole lake or drainage basin. In their view, useful theories for predicting fish production must contain physical, chemical, and biological components of the system. Unlike the quantitative models used by fisheries managers, the limnological view was more conceptual because quantifying food web interactions required intensive, whole-lake studies (Rigler 1982). Similar studies were generally lacking in fisheries science.
Fortunately, we have come a long way in the last 50 years. Limnologists and fisheries biologists recognize that they share a common goal to understand the structure and function of aquatic systems. Indeed, fisheries management challenges are often linked to water quality issues and (or) poor growth and survival of fishes. Thus, understanding food web interactions can help direct management decisions about water quality improvement, fish stocking, macrophyte management, species introductions, or other food web components. In this chapter, factors that influence the structure and function of aquatic food webs are discussed and the implications of food web interactions for fisheries management are explored.