ROV assessment of mesophotic fish and associated habitats across the continental shelf of the Amathole region

Abstract

Understanding how fsh associate with habitats across marine landscapes is crucial to developing efective marine spatial planning (MSP) in an expanding and diversifying ocean economy. Globally, anthropogenic pressures impact the barely understood temperate mesophotic ecosystems and South Africa’s remote Amathole shelf is no exception. The Kei and East London region encompass three coastal marine protected areas (MPAs), two of which were recently extended to the shelf-edge. The strong Agulhas current (exceeding 3 m/s), which runs along the narrow shelf exacerbates sampling challenges. For the frst time, a remotely operated vehicle (ROV) surveyed fsh and their associated habitats across the shelf. Results indicated fsh assemblages difered between the two principle sampling areas, and across the shelf. The number of distinct fsh assemblages was higher inshore and on the shelf-edge, relative to the mid-shelf. However, the mid-shelf had the highest species richness. Unique visuals of rare Rhinobatos ocellatus (Speckled guitarfsh) and shoaling Polyprion americanus (wreckfsh) were collected. Visual evidence of rhodolith beds, deep-water lace corals and critically endangered endemic seabreams were ecologically important observations. The ROV enabled in situ sampling without damaging sensitive habitats or extracting fish.