Additional file 2: of Diel patterns in three-dimensional use of space by sea snakes

Three-dimensional space use by a representative Hydrophis curtus within the study site (Fig. 3a). Day-time core (50%-3DKUD; dark red) and extent (95%-3DKUD; light red) 3DKUD as well as night-time core (50%-3DKUD; dark blue) and extent (95%-3DKUD; light blue) 3DKUD are represented. Surrounding bathymetry and sea surface are also rendered to provide context. Black points represent the locations of acoustic receivers within the study site. For the interactive version of this data please visit https://dl.dropboxusercontent.com/u/31456301/3DSS/SM2/index.html . Close up version of this model is available in Additional file 4

Additional file 3: of Diel patterns in three-dimensional use of space by sea snakes

Three-dimensional space use by a representative Hydrophis elegans within the study site (Fig. 3c). Day-time core (50%-3DKUD; dark red) and extent (95%-3DKUD; light red) 3DKUD as well as night-time core (50%-3DKUD; dark blue) and extent (95%-3DKUD; light blue) 3DKUD are represented. Surrounding bathymetry and sea surface are also rendered to provide context. Black points represent the locations of acoustic receivers within the study site. For the interactive version of this data please visit https://dl.dropboxusercontent.com/u/31456301/3DSS/SM4/index.html . Close up version of this model is available in Additional file 5

DataSheet_1_Video surveys of sea snakes in the mesophotic zone shed light on trends in populations.docx

Declines in abundance of sea snakes have been observed on reefs throughout the Indo-Pacific, although the reasons are unknown. To date, surveys have occurred on shallow reefs, despite sea snakes occurring over a large depth range. It is not known if populations of sea snakes in deep habitats have undergone similar declines. To address this, we analysed deep-water video data from a historical hotspot of sea snake diversity, Ashmore Reef, in 2004, 2016, and 2021. We collected 288 hours of video using baited remote underwater videos and a remotely operated vehicle at depths between 13 and 112 m. We observed 80 individuals of seven species with Aipysurus laevis (n = 30), Hydrophis peronii (n = 8), and H. ocellatus (n = 6) being the most abundant. Five of the species (A. duboisii, A. apraefrontalis, H. ocellatus, H. kingii, and Emydocephalus orarius) had not been reported in shallow waters for a decade prior to our study. We found no evidence of a decline in sea snakes across years in deep-water surveys, although abundances were lower than those in early shallow-water surveys. A comparison of BRUVS data from 2004 and 2016 was consistent with the hypothesis that predation by sharks may have contributed to the loss of sea snakes in shallow habitats. Our study highlights the use of underwater video to collect information on sea snakes in the mesophotic zone and also suggests that future monitoring should include these depths in order to capture a more complete representation of habitats occupied.</p