11: Assessment of Diets and Feeding Patterns
Steven R. Chipps and James E. Garvey
Quantitative assessment of food habits is an important aspect of fisheries management. Successful management of sport fishes often hinges on our ability to manage prey resources (Noble 1981; DeVries and Stein 1990). As a result, knowledge of prey resources can help guide management efforts aimed at increasing fish production. Accurate description of fish diets and feeding habits also provides the basis for understanding trophic interactions in aquatic food webs (Garvey et al. 1998a; Vander Zanden et al. 2000). Diet composition analysis or other techniques, such as stable isotope analysis, can be used to evaluate effects of ontogeny, habitat, or the establishment of exotic species.
Diets of fishes represent an integration of many ecological components that include behavior, condition, habitat use, energy intake and inter- and intraspecific interactions. As a result, food habit studies can be incorporated in a variety of different research objectives. In the simplest case, a food habits study might be conducted to determine the most frequently consumed prey or determine whether a particular food category is present in the stomach of fishes. In other instances, we may be interested in more complex questions, such as (1) determining the relative importance of different food types to fish nutrition, (2) quantifying the consumption rate of individual prey types (Chapter 12), or (3) understanding foraging trade-offs associated with predator avoidance (Chapter 16). Each of these questions requires information on fish diets but necessitates different approaches in how we collect and analyze data. In this chapter, we outline quantitative techniques used to describe food habits and feeding patterns of fishes.