We describe a technique for the quantitative description of social systems produced by aggressive interactions between individuals. The assumption underlying the technique is that individuals often employ one or both of two different strategies to gain access to resources. One strategy is to use an established relationship to claim resources wherever they are found (dominance); the other is to exclude competitors from resources in a specific area (territoriality). Our technique allows us to quantify the degree to which the behavioral dimension of each of these strategies is manifested by each individual and also by the whole set of interacting individuals. It will be possible to correlate the quantified social system variables generated by this approach with quantified ecological variables, such as population density and abundance of food, thus contributing to the development of a more rigorous behavioral ecology.

We illustrate this method with quantitative descriptions of variation in juvenile rainbow trout (Oncorbyn-cus mykiss) correlated with variation in population density and stream flow velocity.