Overview
The Bank Steenbras (Chirodactylus grandis), also known in South Africa as the Butterfish, is an imposing, long-lived morwong fish endemic to the turbulent coastal waters of the Cape. Inhabiting deep offshore reefs and rocky banks where Atlantic and Indian Ocean currents converge, this deep-bodied perciform is recognized by its reddish-brown flank, fleshy lips, and thickened lower pectoral fin rays that it uses like delicate fingertips to probe the seafloor.
Biology and Physical Characteristics
Chirodactylus grandis features an arched, compressed body profile with large, smooth cycloid scales. Its coloration ranges from golden-bronze to warm reddish-brown on the upper dorsal surface, fading to creamy silver on the belly. The head is large with prominent bulbous eyes adapted for low-light vision in deep water, complemented by thick rubbery lips housing small, conical crushing teeth. The most remarkable feature of the bank steenbras is its pectoral fins: the lower five to seven rays are unbranched, thickened, and free of membranes at their tips, packed with mechanoreceptors and chemoreceptors that allow the fish to ‘walk’ along rock faces and detect buried prey.
Behavior and Ecology
Operating primarily as a solitary or small-group bottom dweller, the bank steenbras cruises deep reef slopes, using its sensory pectoral rays to feel through gravel crevices for crabs, sea urchins, and polychaetes. When prey is detected, its powerful jaws crush the hard exoskeletons with ease. Slow-growing and late to reach sexual maturity, adults spawn during winter months along offshore banks, with pelagic larvae drifting in ocean currents before settling onto rocky reefs.
Conservation and Human Impact
Assessed as Vulnerable by the IUCN due to historic commercial linefishing and recreational overexploitation, Chirodactylus grandis has suffered significant population depletion. Because of its longevity, site fidelity to specific offshore pinnacles, and slow reproductive turnover, localized banks have experienced severe declines. South African fisheries authorities have enacted strict bag limits, minimum size restrictions, and marine protected area zones (such as the Tsitsikamma National Park) to facilitate population recovery.
Interesting Factoid
The bank steenbras has finger-like spikes growing out of its lower fins that have a sense of touch and taste, allowing it to literally ‘walk’ across the sea bottom and taste for hidden crabs under rocks!
Last updated: October 2026