Notes on a remotely operated vehicle survey to describe reef ichthyofauna and habitats-Agulhas Bank, South Africa

Background: Despite their ecological and economic importance, reef habitats on the central Agulhas Bank, off the southern tip of Africa, remain poorly studied. The ichthyofauna of these habitats cannot be surveyed using trawl gear. Objective: Preliminary assessment of the use of a remotely operated vehicle (ROV) to investigate the ichthyofauna associated with deep reef habitats on the central Agulhas Bank. Method: Underwater visual surveys were carried out during ROV dives (maximum duration 60 minutes; area covered approximately 800 m2; maximum dive depth 100 m). Results & discussion: The number of detected fish species (36) compares well with that reported from fishing surveys and commercial fisher data. Most (68%) fishes appeared to be undisturbed by the ROV. Species saturation was reached after a maximum of 135 minutes survey time, but species numbers increased and saturation times shortened (34 minutes minimum) with the introduction of bait. Conclusion: ROV surveys may represent a non-extractive alternative to assess demersal ichthyofaunal diversity in relation to habitat structure and benthic cover on temperate reefs around South Africa.