Web Ecology 1: 1–10.

The study of life-history theory is of fundamental impor-tance to the analysis of population performance and thus to both theoretical ecology and resource management. Life-history theory is based on the concept of trade-off constraints between alternative energy-consuming func-tions, and the resulting balance between life history traits tends to maximize fitness (i.e. total reproductive output) (e.g. Beverton 1963, Roff 1992, Stearns 1992, Charnov 1993). When various life-history parameters (e.g. growth, maturation and mortality) are plotted against each other for a large number of fish species, clear patterns emerge (e.g. Pauly 1998a, Froese and Pauly 1998). Thus, for in-stance, tropical fishes are smaller, attain their asymptotic sizes faster, have for any given asymptotic size higher natu-ral mortality, and have higher trophic levels than their colder counterparts (Pauly 1998a). Several empirical stud-ies on fishes have shown that some of the emerging pat-terns are consistent with the trade-off concept (e.g. nega-tive correlations between current reproduction and some component of fitness, usually survival of offspring, mortal