Abstract
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.
Highlights
Surveys of the marine ichthyofauna associated with temperate reefs are challenging because, unlike soft sediment, these habitats cannot be surveyed with trawl gear (Sink et al 2012)
Reefs often harbour complex species assemblages, stratified according to physical and biological gradients (Ross & Quattrini 2007; Söffker, Sloman & Hall-Spencer 2011). Survey methods for such habitats have mostly been confined to diver-based underwater visual census (UVC) for shallow depths (30 m) (Söffker et al 2011)
We report on the first remotely operated vehicle (ROV) dives to investigate the deep reef ichthyofauna and its associated habitats on the central Agulhas Bank
Summary
Surveys of the marine ichthyofauna associated with temperate reefs are challenging because, unlike soft sediment, these habitats cannot be surveyed with trawl gear (Sink et al 2012). Reefs often harbour complex species assemblages, stratified according to physical and biological gradients (Ross & Quattrini 2007; Söffker, Sloman & Hall-Spencer 2011) Survey methods for such habitats have mostly been confined to diver-based underwater visual census (UVC) for shallow depths (30 m) (Söffker et al 2011). In addition to general habitat observations, we were interested in (1) fish behaviour towards a ROV, (2) deployment times sufficient to detect representative species assemblages and (3) the number of fish species detected relative to other surveys 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
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