The HROV Nereus was used to conduct exploration and characterization (including downloading video seafloor transects) of the Kermadec Trench region in May 2014. Geo-referenced vehicle navigation was conducted using the R/V Thompson’s GPS launch position of the vehicle, the estimated initial on bottom position of the vehicle, the course over ground (determined by the Gyro heading, Doppler Velocity Profiler, and thruster speed).

The HROV transected between 1 and 5 meters off the seafloor, utilizing a down-looking Sony 4k HD camera system, in collaboration with the Advanced Imaging and Visualization Lab at the Woods Hole Oceanographic Institution. Megafauna was enumerated via direct counts from continuous video. Taxonomic identifications were based on comparison with published morphological characters when possible.

Nereus transect video was annotated using CADTV version 11 software and geo-referencing of continuous navigation was conducted via Matlab (2011 Release; MathWorks, Inc.) and Microsoft Excel for Mac 14.7.3.

Summary of HADES-K Nereus dives:

Nereus Dive #	Date	Mission Depth (m)	Dive Duration (hrs:min)	# of Transects	Bottom Duration (hrs:min)
64	4/14/2014	4000	12:00	1	6:41
72	5/2/2014	6060	17:19	4	9:28
73	5/4/2014	7000	18:04	2	8:09
74	5/5/2014	8100	19:57	1	10:07
75	5/8/2014	9000	13:44	0	2:16
76	5/10/2014	10,000	11:54	2	6:28