Abstract
Marine protected areas (MPAs) have become a crucial conservation strategy in response to anthropogenic threats impacting the world’s oceans. However, some MPAs have conflicting goals that compromise conservation effectiveness. To guide future MPA development, the conservation value of current MPAs need to be accurately quantify using diversity metrics, such as species richness and rarity. This study focused on the demersal soft-sediment fauna of the Western Indian Ocean (WIO) and explored their environmental predictors and distributions. Hotspot areas of high species richness and rare taxa were identified, comparing them to existing MPAs, to evaluate their value as a conservation strategy for these fauna. The results show that depth, which negatively correlates with water temperature, and latitude, which positively correlates with longitude, are the most influential predictors of demersal species richness and rarity. Various other environmental factors are significantly associated with these two diversity measures. Hotspots of species richness and rarity occur in deeper, cooler waters away from the coastline, which are less exposed to disturbances. Higher richness was found outside of MPAs, likely because most WIO MPAs are in shallow waters, while the studied demersal fauna favour deeper conditions. These findings underscore the need for MPAs to comprise a mosaic of habitat types to effectively conserve the diversity of demersal species.