Species Diversity, Abundance, and Biomass of Fish at Offshore Platforms in the Arabian Gulf

Johan Mølgård Sørensen^1,2*Felipe Torquato²Lauren Faulkner³Christopher G. Lowe³Mathieu Carrara⁴Alexei Godina⁴Fahad Al-Jamali²Radhouan Ben-Hamadou^2,5Peter Rask Møller¹Pedro Range^6*

• ¹Natural History Museum of Denmark, University of Copenhagen, Copenhagen, Denmark
• ²Department of Biological and Environmental Sciences, College of Arts and Sciences, Qatar University, Doha, Qatar
• ³Department of Biological Sciences, California State University Long Beach, Long Beach, California, United States
• ⁴TotalEnergies Research Center Qatar, TotalEnergies EP Qatar, Doha, Qatar
• ⁵Earthna Center for a Sustainable Future, Qatar Foundation, Doha, Qatar
• ⁶Environmental Science Center, Qatar University, Doha, Qatar

This study explored fish assemblages associated with platform artificial reefs in Qatar's Al Khalij oilfield using remotely operated vehicle (ROV) video surveys. We assessed species diversity, abundance, and biomass across depth gradients to understand the ecological role of offshore platforms in supporting marine life within the Arabian Gulf. By surveying the full water column around two platforms, we counted 4,474 fishes, estimated a total biomass of 6,184 kg per platform, and identified 46 taxa, with Carangidae (jacks) and Serranidae (groupers) as the most diverse families, and Pinjalo pinjalo (Pinjalo), Scomberoides commersonnianus (Talang queenfish), and Lutjanus argentimaculatus (mangrove red snapper) as the most abundant species. A clear stratification in assemblage was observed with increasing depth: Carangidae dominated surface layers, while Serranidae were prevalent near the seafloor. The reefing effect of the platforms was evident, with benthopelagic species, such as Pomacanthus maculosus (yellowbar angelfish), Acanthopagrus bifasciatus (twobar seabream), and Heniochus acuminatus (pennant coralfish), observed throughout the water column. Abundance and biomass generally declined with depth, although hotspots occurred near structurally complex areas and the seafloor. Comparisons with studies from Qatar's Al Shaheen oilfield, 120 km northwest, revealed differences in species composition, likely due to variations in structural complexity, platform size, and geographic location, as well as differences in sampling design. While ROV surveys proved valuable, visibility constraints highlighted the need for complementary methods, such as eDNA metabarcoding, to enhance species detection. These findings provided insights into the biodiversity supported by offshore platforms, informing Rigs-to-Reefs initiatives aimed at enhancing marine biodiversity in the Arabian Gulf.