Some methods available for the study of the population dynamics of tropical fish are reviewed; emphasis is given to questions of growth, mortality and recruitment, and to relatively new approaches, such as aging by means of daily otolith structures, detailed analysis of length-frequency data and to comparative studies. A package of methods is discussed which is based on a set of 3 new, simple computer programs written in BASIC for the analysis of length-frequency data (ELEFAN I, II and III)