Connectivity is a key factor in metacom- munity ecology, because it influences dispersal and colonization rates. However, it has received less attention in aquatic than in terrestrial ecology research. We investigated whether connectivity is a good predictor of species richness in functional fish communities (freshwater, FS; estuarine, ES and estu- arine-freshwater, EFS) from 31 coastal lakes in southern Brazil. We used a model selection approach, including lake area and distance from the ocean as additional predictors of species richness and two connectivity metrics: primary connectivity (CP) and estuarine connectivity (CE), which measure connec- tivity to neighboring lakes and system-wide connec- tivity, respectively. Both metrics estimate functional connectivity and were calculated on habitat-based cost distances. Connectivity was more important for pre- dicting richness of functional communities than for total richness, particularly CE, which was distinctively related to each functional fish community richness (directly related to ES and EFS, and inversely related to FS; CP was related only to ES). Remarkably, connectivity was more important than area for predicting ES and EFS richness. These results add support to dispersal limitation as an important mech- anism influencing fish communities. We suggest that incorporating environmental filters (habitat type) to quantify connectivity is useful for accessing the patterns of species richness.