SPYING ON ELASMOBRANCHS: DIVERSITY AND ABUNDANCE USING BRUVS IN ZAVORA BAY, MOZAMBIQUE

Student: 
Alexandra Hanusch

The marine life of Zavora Bay, Mozambique, is highly diverse however the ecology of elasmobranchs is poorly understood. The aim of this study was to investigate the diversity and abundance of elasmobranchs in the coastal waters of Zavora using baited remote underwater video systems (BRUVs). Twenty-five BRUV deployments were performed between January and May 2019 for over 60 mins in depths of 16 to 33 m. Generally, there was a low elasmobranch diversity and abundance observed. The BRUV recorded total of 31 elasmobranch individuals, representing 27.27 % of known elasmobranch species for Zavora Bay. Depth was identified to significantly affect the mean relative abundance of elasmobranchs (MaxN). Brillouin Index (HB) presented that the deep reefs were the most diverse areas. At deep reefs, Taeniura meyeni and Neotrygon kuhlii were the most common species. The UVC surveys showed that elasmobranchs are more abundant at deep reefs than at shallow ones. In both methods, T. meyeni and N. kuhlii were more often observed than other species. Interestingly, UVC recorded more individuals and elasmobranch species than the BRUV method. This study demonstrates the importance of BRUVs to rapidly obtain estimates of elasmobranch diversity and abundance, especially under rough and turbid water conditions