Biotic interactions: I. Predation and parasitism

Abstract

Abiotic factors such as temperature and oxygen set limits on where individual fish can survive and these factors influence the patterns of allocation of time and material resources by individuals (see Chapter 4). Within the limits set by abiotic factors, encounters with other organisms can also change an individual’s risk of dying or change its pattern of allocation of time and resources with consequences for its growth and reproduction. Encounters which result in the fish feeding or mating have already been described (see Chapters 3 and 7); other types of encounter are the subject of this chapter and the next. Interactions with other organisms are of a fundamentally different nature from interactions with abiotic factors because the fitnesses of all the interacting organisms may be affected. The outcome of a biotic interaction may have consequences for the distribution, abundance and genetic composition of the populations of which the interacting organisms are members and for the species composition of the assemblage present in a location (see Chapter 12 for a discussion of assemblages). But even if the consequences of the interactions are more easily observed through changes at the population or assemblage level, these consequences result from the effects of the interactions on the individual participants.