The adaptive significance of locomotor, specifically orientation responses in fishes to environmental stimuli, is emphasized. General locomotor behavior is usually extremely variable over time whereas the responses mentioned are, most frequently, very subtle.

Techniques are described to detect and quantify these responses by comparing locomotion before stimulation with that during exposure to the environmental variable(s) under study. Models for such comparison are based on time series analysis of relevant locomotor variables, such as frequency and size of turns, length and orientation of steps, velocity, and others. Two techniques for data acquisition of these variables, by means of electronic monitoring of locomotion under controlled physical and chemical conditions, are described in some detail.

Attention is called to the possible interaction of environmental conditions and the behavioral responses of fish, an aspect which, hitherto, has received too little consideration in studies on biological effects of environmental variables.