The definition, nomenclature, methodology, main aspec ts and research directions of the ecomorphology (or ecological morphology) of fi sh were reviewed on the basis of collected literatures in this paper. Ecomorphol ogy is a comparative discipline; the central goal is the study of the interactio ns between the morphology of organisms and their ecology both in the present and over evolutionary time. These interactions can be studied at multiple levels: a mong individuals within a species, among species and higher taxa, among guilds a nd communities. From an ecological perspective ecomorphological studies have thr ee aims: (1) measurements of the correlation between general morphological varia tion and ecological variation; (2) making ecological inferences from morphologic al pattern; (3) determination of the underlying morphological mechanism that inf luences resource use by an organism and the degree to which ecomorphological rel ationships are influenced by other factors. The main aspects of ecomorphological research include application of a more functional approach to the choice of cha racters, integration of morphological, behavioral, and physiological information to address adaptation, and the expansion of spatial and temporal (ontogenetic a nd evolutionary) scales of ecomorphological questions. In the future, research d irections for ecomorphology include additions to the knowledge base, further int egration of information from other disciplines, examination of the relative cont ribution of genetic versus environmental factors in producing and maintaining ec ological and morphological diversity, and insights from ecomorphological studies used to reveal the composition of ecological communities and predict the impact s on existing communities by biotic or abiotic disturbance, including species in troductions or other anthropogenic manipulations.