† Paul J Clerkin1*, James D S Knuckey1, and David A Ebert 1
BIODIVERSITY AND ENDEMISM OF WESTERN INDIAN OCEAN CHONDRICHTHYANS
1-Pacific Shark Research Center, Moss Landing Marine Laboratories, 8272 Moss Landing Road, Moss Landing, CA 95039, USA, Poster Presentation, 2014 Sharks International, Durban, South, Africa, 2014 **Not present
Abstract: The Western Indian Ocean (WIO) is habitat to over 280 species of Chondrichthyans, a number that represents 23.4% of known Chondrichthyan species, and comprises 152 species of sharks, 121 species of batoids, and 8 species of chimaera. Yet, biodiversity of WIO Chondrichthyans is relatively unknown compared to other diverse, but better studied regions. The most species-rich groups within the WIO are Carcharhiniformes (82 species), Myliobatiformes (46 species), Squaliformes (36 species), and Rajiformes (29 species.) The proximity of the WIO to the Indo-Pacific, a region shown to be a center of origin for the marine tropics, could account for the relatively high number of WIO Chondrichthyan species. Most WIO Chondrichthyans are coastal species, and this might explain why certain groups known to inhabit the deeper waters of the tropics, e.g., Rajiformes, are reported in lower numbers than in other regions. Within the region, seamount ecosystems appear to be hotspots of biodiversity and show a high degree of endemism compared to continental shelf and upper slope habitats. A recent survey collected at depths of 500 m–1,500 m along seamounts of the Madagascar Ridge includes 8 undescribed species along with 23 species of the genera Centrophorus, Deania, Centroscymnus, Centroselachus, Proscymnodon, Zameus, Etmopterus, Dalatias, Apristurus, Bythaelurus, Pseudotriakis, Hydrolagus, and Chimaera. The majority of Chondrichthyan species found in the WIO are listed as Data Deficient (100 species), Near Threatened (54 species), or Vulnerable (51 species) on the IUCN Red List. Enhanced identification of WIO Chondrichthyans is crucial for developing improved management and conservation policies for this group.
Keywords: biodiversity, Western Indian Ocean, deep-sea, new species