The status of Indian Ocean shark and ray communities

Sharks and rays in the Indian Ocean are thought to be under increasing pressure from over fishing and habitat degradation, although the current status of populations is unknown in many countries. To address this gap in... [ view full abstract ]

Sharks and rays in the Indian Ocean are thought to be under increasing pressure from over fishing and habitat degradation, although the current status of populations is unknown in many countries. To address this gap in knowledge, shark and ray communities throughout the region were surveyed using baited remote underwater video stations as part of the Global FinPrint Project. More than 6,700 deployments across 13 countries were made during daylight hours for 60-minute periods. A total of 38 species of sharks were recorded of which >77% of observations were Carcharhinus melanopterus, C. amblyrhynchos and Triaenodon obesus. A total of 32 species of rays were recorded of which the most common species Neotrygon Kuhlii made up 12.5% of observations. Mean relative abundance hr^-1 across the region for sharks was 0.86 ± 0.02 SE, while it was considerably lower for rays at 0.15 ± 0.01 SE. Countries that had relatively high shark abundance (>0.5 sharks hr^-1) included Australia, Maldives, Mozambique, Seychelles, and South Africa. Rays were relatively high in abundance (>0.2 rays hr^-1) in Mozambique, South Africa, and Maldives. Only 45% of countries surveyed had all components of the trophic community represented (High, Medium, and Low trophic positions). Drivers of community level patterns are discussed and related to current management and conservation measures.