Animal decision making and its ecological consequences: the future of aquatic ecology and behaviour

It is virtually impossible to predict the next 25 years of research in aquatic ecology and behaviour with any accuracy. However, by identifying those areas that are the current frontiers of the discipline it is possible to guess at the most likely research developments over the next decade. From my own biased perspective, the research programme most likely to be productive in the near future is that of behavioural ecology, which studies, among other things, animal decision making in an ecological context. I focus on situations in which animals must make decisions under conflicting objectives, e.g., to simultaneously maximize net energy intake while minimizing risk of predation. New data on guppies (Poecilia reticulata) are presented and the recent literature is reviewed to support the notion that animals in such situations behave so as to maximize fitness. Habitat choices, ontogenetic habitat shifts, and the phenomena of vertical migration and downstream drift are beginning to be considered in this general evolutionary framework, with novel results, and this trend will undoubtedly continue. Extension of the logic of trade-offs to the community level leads to a number of new insights about the processes that shape community structure, and affirms the need for aquatic ecologists of the future to have a thorough understanding of animal behaviour, and a working knowledge of such tools of evolutionary ecology as optimality reasoning and game theory.