Rocky reefs and sandy areas near reefs at depths to 240 m. Juveniles may be found in rock pools.
C. brachydactylus is a small-benthic-invertebrate predator, There is some dietary overlap between the species assembages of the reef predators, in which this fish occurs, but each appears to have a dietary niche which reduces interspecific competition for food. Its diet includes crabs, anphipods, bivalves and other invertebrates.
C. brachydactylis is preyed upon by large reef predators, including the santer seabream, (
Cheimerius nufar), red steenbras (
Petrus rupestris), scotsman (
Polysteganus praeorbitalis), and yellowbelly rockcod (
Epinephelus marginatus). ==Importance to humans==