We investigated spatio-temporal variability in the abundances and biomasses of four species of inshore serranids (the dusky grouper Ephinephelus marginatus, the island grouper Mycteroperca fusca, the painted comber Serranus scriba, and the blacktail comber S. atricauda) throughout the Canarian Archipelago (central-east Atlantic Ocean) with underwater visual transects. By means of a multiscaled sampling design spanning three orders of magnitude of spatial variability (from 10 s of meters among replicated 100 m2 transects to 100 s of kilometres among islands) and four sampling periods, we related differences in the distributions of serranids to differences in the degree of human pressure, such as fishing intensity and human population. Differences in human pressure among islands provide the most parsimonious explanation for many of the consistent inter-island differences in the abundance and biomass of the analyzed species. Larger-bodied serranids (E. marginatus and M. fusca) are more vulnerable than the smaller species (S. scriba and S. atricauda). In fact, the larger, more vulnerable species have been almost completely extirpated from the most intensely fished islands. Our results show that the larger groupers have been overexploited throughout the Canary Islands, and highlight the urgent need for stringent management measures and better control of littoral reef fish resources.