It is generally assumed that fish populations are regulated primarily in the juvenile (pre–recruit) phase of the life cycle, although density dependence in growth and reproductive parameters within the recruited phase has been widely reported. Here we present evidence to suggest that density–dependent growth in the recruited phase is a key process in the regulation of many fish populations. We analyse 16 fish populations with long–term records of size–at–age and biomass data, and detect significant density–dependent growth in nine. Among–population comparisons show a close, inverse relationship between the estimated decline in asymptotic length per unit biomass density, and the long–term average biomass density of populations. A simple population model demonstrates that regulation by density–dependent growth alone is sufficient to generate the observed relationship. Density–dependent growth should be accounted for in fisheries' assessments, and the empirical relationship established here can provide indicative estimates of the density–dependent growth parameter where population–specific data are lacking.