Methods for Fish Biology

Chapter 18: Autecology

Donald M. Baltz


Autecology is the study of single-species ecology. Many of the techniques used in autecology, such as methods to determine reproductive cycles, have been described elsewhere in this book (for other purposes) as well as in Fisheries Techniques (Nielsen and Johnson 1983). I draw them together in this chapter and describe in detail the ways to study microhabitat use by fishes. Box 18.1 contains a glossary of key ecological terms used in this chapter.

Interrelations of species are the focus of synecology, treated in Chapter 19. Synecologists use many autecological techniques because community dynamics cannot be understood unless the ecology of component species is known. Hixon (1980), Larson (1980), and Fausch and White (1981) are among those who have integrated aut- and synecology in their work.

Autecology comprises studies of a species’ life history and environmental requirements.

A life history study primarily addresses the way in which a species lives. The usual characteristics of interest are age-specific growth rates, longevity, survivorship, reproduction, feeding habits, behavior, and general life history strategy.

A study of environmental requirements deals with a species’ niche dimensions or axes (see niche, Box 18.1). Relevant physicochemical niche dimensions include temperature, light, water depth and velocity, dissolved oxygen concentration, salinity, and pH. Most descriptions of fish microhabitats emphasize the physical characteristics of sites or locations occupied by individual fish such as depth, substrate, and cover. Chemical variables often receive less attention because they normally do not vary much within an environment, but they should be described in detail when they do vary and especially when one or more of them determines the suitability of a habitat for spawning or some other important function (see, for example, Matthews and Hill 1977, 1979a, 1979b).

The goal of an environmental requirements study is to describe a species’ niche—that is, how the species uses resources—in the fundamental sense without the presence of other species. However, niche dimensions measured in the field probably are restricted by competitors, predators, and symbionts (Hutchinson 1958; Colwell and Futuyama 1971; Hurlbert 1981). The influences of other species may not be immediately apparent, so inferences about fundamental niches should be made cautiously if field data are not supported by laboratory studies (Baltz et al. 1982).